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Merge pull request #323 from appleboy/patch-9

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fix: coding style and file format for all example.
This commit is contained in:
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2017-02-11 00:06:18 -05:00
committed by GitHub
parent da57568722 416e29d95a
commit 65085a87c7
206 changed files with 5531 additions and 5451 deletions
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87
eBook/examples/chapter_10/embed_func1.go
View File

@@ -1,43 +1,44 @@
package main
import (
"fmt"
)
type Log struct {
msg string
}
type Customer struct {
Name string
log *Log
}
func main() {
// c := new(Customer)
// c.Name = "Barak Obama"
// c.log = new(Log)
// c.log.msg = "1 - Yes we can!"
// shorter:
c := &Customer{"Barak Obama", &Log{"1 - Yes we can!"}}
// fmt.Println(c) // &{Barak Obama 1 - Yes we can!}
c.Log().Add("2 - After me the world will be a better place!")
//fmt.Println(c.log)
fmt.Println(c.Log())
}
func (l *Log) Add(s string) {
l.msg += "\n" + s
}
func (l *Log) String() string {
return l.msg
}
func (c *Customer) Log() *Log {
return c.log
}
/* Output:
1 - Yes we can!
2 - After me the world will be a better place!
*/
package main
import (
"fmt"
)
type Log struct {
msg string
}
type Customer struct {
Name string
log *Log
}
func main() {
// c := new(Customer)
// c.Name = "Barak Obama"
// c.log = new(Log)
// c.log.msg = "1 - Yes we can!"
// shorter:
c := &Customer{"Barak Obama", &Log{"1 - Yes we can!"}}
// fmt.Println(c) // &{Barak Obama 1 - Yes we can!}
c.Log().Add("2 - After me the world will be a better place!")
//fmt.Println(c.log)
fmt.Println(c.Log())
}
func (l *Log) Add(s string) {
l.msg += "\n" + s
}
func (l *Log) String() string {
return l.msg
}
func (c *Customer) Log() *Log {
return c.log
}
/* Output:
1 - Yes we can!
2 - After me the world will be a better place!
*/

76
eBook/examples/chapter_10/embed_func2.go
View File

@@ -1,38 +1,38 @@
package main
import (
"fmt"
)
type Log struct {
msg string
}
type Customer struct {
Name string
Log
}
func main() {
c := &Customer{"Barak Obama", Log{"1 - Yes we can!"}}
c.Add("2 - After me the world will be a better place!")
fmt.Println(c)
}
func (l *Log) Add(s string) {
l.msg += "\n" + s
}
func (c *Customer) String() string {
return c.Name + "\nLog:" + fmt.Sprintln(c.Log)
}
func (l *Log) String() string {
return l.msg
}
/* Output:
Barak Obama
Log:{1 - Yes we can!
2 - After me the world will be a better place!}
*/
package main
import (
"fmt"
)
type Log struct {
msg string
}
type Customer struct {
Name string
Log
}
func main() {
c := &Customer{"Barak Obama", Log{"1 - Yes we can!"}}
c.Add("2 - After me the world will be a better place!")
fmt.Println(c)
}
func (l *Log) Add(s string) {
l.msg += "\n" + s
}
func (c *Customer) String() string {
return c.Name + "\nLog:" + fmt.Sprintln(c.Log)
}
func (l *Log) String() string {
return l.msg
}
/* Output:
Barak Obama
Log:{1 - Yes we can!
2 - After me the world will be a better place!}
*/

36
eBook/examples/chapter_10/embedd_struct.go
View File

@@ -1,18 +1,18 @@
package main
import "fmt"
type A struct {
ax, ay int
}
type B struct {
A
bx, by float32
}
func main() {
b := B{A{1, 2}, 3.0, 4.0}
fmt.Println(b.ax, b.ay, b.bx, b.by)
fmt.Println(b.A)
}
package main
import "fmt"
type A struct {
ax, ay int
}
type B struct {
A
bx, by float32
}
func main() {
b := B{A{1, 2}, 3.0, 4.0}
fmt.Println(b.ax, b.ay, b.bx, b.by)
fmt.Println(b.A)
}

33
eBook/examples/chapter_10/main.go
View File

@@ -1,16 +1,17 @@
package main
import (
"fmt"
"./struct_pack/structPack"
)
func main() {
struct1 := new(structPack.ExpStruct)
struct1.Mi1 = 10
struct1.Mf1 = 16.
fmt.Printf("Mi1 = %d\n", struct1.Mi1)
fmt.Printf("Mf1 = %f\n", struct1.Mf1)
}
// Mi1 = 10
// Mf1 = 16.000000
package main
import (
"./struct_pack/structPack"
"fmt"
)
func main() {
struct1 := new(structPack.ExpStruct)
struct1.Mi1 = 10
struct1.Mf1 = 16.
fmt.Printf("Mi1 = %d\n", struct1.Mi1)
fmt.Printf("Mf1 = %f\n", struct1.Mf1)
}
// Mi1 = 10
// Mf1 = 16.000000

58
eBook/examples/chapter_10/method1.go
View File

@@ -1,29 +1,29 @@
package main
import "fmt"
type TwoInts struct {
a int
b int
}
func main() {
two1 := new(TwoInts)
two1.a = 12
two1.b = 10
fmt.Printf("The sum is: %d\n", two1.AddThem())
fmt.Printf("Add them to the param: %d\n", two1.AddToParam(20))
// literal:
two2 := TwoInts{3, 4}
fmt.Printf("The sum is: %d\n", two2.AddThem())
}
func (tn *TwoInts) AddThem() int {
return tn.a + tn.b
}
func (tn *TwoInts) AddToParam(param int) int {
return tn.a + tn.b + param
}
package main
import "fmt"
type TwoInts struct {
a int
b int
}
func main() {
two1 := new(TwoInts)
two1.a = 12
two1.b = 10
fmt.Printf("The sum is: %d\n", two1.AddThem())
fmt.Printf("Add them to the param: %d\n", two1.AddToParam(20))
// literal:
two2 := TwoInts{3, 4}
fmt.Printf("The sum is: %d\n", two2.AddThem())
}
func (tn *TwoInts) AddThem() int {
return tn.a + tn.b
}
func (tn *TwoInts) AddToParam(param int) int {
return tn.a + tn.b + param
}

32
eBook/examples/chapter_10/method2.go
View File

@@ -1,16 +1,16 @@
package main
import "fmt"
type IntVector []int
func (v IntVector) Sum() (s int) {
for _, x := range v {
s += x
}
return
}
func main() {
fmt.Println(IntVector{1, 2, 3}.Sum()) // Output: 6
}
package main
import "fmt"
type IntVector []int
func (v IntVector) Sum() (s int) {
for _, x := range v {
s += x
}
return
}
func main() {
fmt.Println(IntVector{1, 2, 3}.Sum()) // Output: 6
}

48
eBook/examples/chapter_10/method3.go
View File

@@ -1,24 +1,24 @@
package main
import (
"fmt"
"math"
)
type Point struct {
x, y float64
}
func (p *Point) Abs() float64 {
return math.Sqrt(p.x*p.x + p.y*p.y)
}
type NamedPoint struct {
Point
name string
}
func main() {
n := &NamedPoint{Point{3, 4}, "Pythagoras"}
fmt.Println(n.Abs()) // prints 5
}
package main
import (
"fmt"
"math"
)
type Point struct {
x, y float64
}
func (p *Point) Abs() float64 {
return math.Sqrt(p.x*p.x + p.y*p.y)
}
type NamedPoint struct {
Point
name string
}
func main() {
n := &NamedPoint{Point{3, 4}, "Pythagoras"}
fmt.Println(n.Abs()) // prints 5
}

56
eBook/examples/chapter_10/method4.go
View File

@@ -1,28 +1,28 @@
package main
import (
"fmt"
"math"
)
type Point struct {
x, y float64
}
func (p *Point) Abs() float64 {
return math.Sqrt(p.x*p.x + p.y*p.y)
}
type NamedPoint struct {
Point
name string
}
func (n *NamedPoint) Abs() float64 {
return n.Point.Abs() * 100.
}
func main() {
n := &NamedPoint{Point{3, 4}, "Pythagoras"}
fmt.Println(n.Abs()) // prints 500
}
package main
import (
"fmt"
"math"
)
type Point struct {
x, y float64
}
func (p *Point) Abs() float64 {
return math.Sqrt(p.x*p.x + p.y*p.y)
}
type NamedPoint struct {
Point
name string
}
func (n *NamedPoint) Abs() float64 {
return n.Point.Abs() * 100.
}
func main() {
n := &NamedPoint{Point{3, 4}, "Pythagoras"}
fmt.Println(n.Abs()) // prints 500
}

51
eBook/examples/chapter_10/method_on_time.go
View File

@@ -1,25 +1,26 @@
// method_on_time.go
package main
import (
"fmt"
"time"
)
type myTime struct {
time.Time //anonymous field
}
func (t myTime) first3Chars() string {
return t.Time.String()[0:3]
}
func main() {
m := myTime{time.Now()}
fmt.Println("Full time now:", m.String()) //calling existing String method on anonymous Time field
fmt.Println("First 3 chars:", m.first3Chars()) //calling myTime.first3Chars
}
/* Output:
Full time now: Mon Oct 24 15:34:54 Romance Daylight Time 2011
First 3 chars: Mon
*/
// method_on_time.go
package main
import (
"fmt"
"time"
)
type myTime struct {
time.Time //anonymous field
}
func (t myTime) first3Chars() string {
return t.Time.String()[0:3]
}
func main() {
m := myTime{time.Now()}
fmt.Println("Full time now:", m.String()) //calling existing String method on anonymous Time field
fmt.Println("First 3 chars:", m.first3Chars()) //calling myTime.first3Chars
}
/* Output:
Full time now: Mon Oct 24 15:34:54 Romance Daylight Time 2011
First 3 chars: Mon
*/

52
eBook/examples/chapter_10/method_string.go
View File

@@ -1,27 +1,25 @@
package main
import (
"fmt"
"strconv"
)
type TwoInts struct {
a int
b int
}
func main() {
two1 := new(TwoInts)
two1.a = 12
two1.b = 10
fmt.Printf("two1 is: %v\n", two1)
fmt.Println("two1 is:", two1)
fmt.Printf("two1 is: %T\n", two1)
fmt.Printf("two1 is: %#v\n", two1)
}
func (tn *TwoInts) String() string {
return "(" + strconv.Itoa(tn.a) + " / " + strconv.Itoa(tn.b) + ")"
}
package main
import (
"fmt"
"strconv"
)
type TwoInts struct {
a int
b int
}
func main() {
two1 := new(TwoInts)
two1.a = 12
two1.b = 10
fmt.Printf("two1 is: %v\n", two1)
fmt.Println("two1 is:", two1)
fmt.Printf("two1 is: %T\n", two1)
fmt.Printf("two1 is: %#v\n", two1)
}
func (tn *TwoInts) String() string {
return "(" + strconv.Itoa(tn.a) + " / " + strconv.Itoa(tn.b) + ")"
}

45
eBook/examples/chapter_10/methodset1.go
View File

@@ -1,22 +1,23 @@
// methodset1.go
package main
import (
"fmt"
)
type List []int
func (l List) Len() int { return len(l) }
func (l *List) Append(val int) { *l = append(*l, val) }
func main() {
// A bare value
var lst List
lst.Append(1)
fmt.Printf("%v (len: %d)\n", lst, lst.Len()) // [1] (len: 1)
// A pointer value
plst := new(List)
plst.Append(2)
fmt.Printf("%v (len: %d)\n", plst, lst.Len()) // &[2] (len: 1)
}
// methodset1.go
package main
import (
"fmt"
)
type List []int
func (l List) Len() int { return len(l) }
func (l *List) Append(val int) { *l = append(*l, val) }
func main() {
// A bare value
var lst List
lst.Append(1)
fmt.Printf("%v (len: %d)\n", lst, lst.Len()) // [1] (len: 1)
// A pointer value
plst := new(List)
plst.Append(2)
fmt.Printf("%v (len: %d)\n", plst, lst.Len()) // &[2] (len: 1)
}

69
eBook/examples/chapter_10/mult_inheritance.go
View File

@@ -1,34 +1,35 @@
// mult_inheritance.go
package main
import "fmt"
type Camera struct { }
func (c *Camera) TakeAPicture() string {
return "Click"
}
type Phone struct { }
func (p *Phone ) Call() string {
return "Ring Ring"
}
// multiple inheritance
type CameraPhone struct {
Camera
Phone
}
func main() {
cp := new(CameraPhone)
fmt.Println("Our new CameraPhone exhibits multiple behaviors ...")
fmt.Println("It exhibits behavior of a Camera: ", cp.TakeAPicture())
fmt.Println("It works like a Phone too: ", cp.Call())
}
/* Output:
Our new CameraPhone exhibits multiple behaviors ...
It exhibits behavior of a Camera: Click
It works like a Phone too: Ring Ring
*/
// mult_inheritance.go
package main
import "fmt"
type Camera struct{}
func (c *Camera) TakeAPicture() string {
return "Click"
}
type Phone struct{}
func (p *Phone) Call() string {
return "Ring Ring"
}
// multiple inheritance
type CameraPhone struct {
Camera
Phone
}
func main() {
cp := new(CameraPhone)
fmt.Println("Our new CameraPhone exhibits multiple behaviors ...")
fmt.Println("It exhibits behavior of a Camera: ", cp.TakeAPicture())
fmt.Println("It works like a Phone too: ", cp.Call())
}
/* Output:
Our new CameraPhone exhibits multiple behaviors ...
It exhibits behavior of a Camera: Click
It works like a Phone too: Ring Ring
*/

54
eBook/examples/chapter_10/new_make.go
View File

@@ -1,27 +1,27 @@
// annoy1.go
package main
type Foo map[string]string
type Bar struct {
thingOne string
thingTwo int
}
func main() {
// OK:
y := new(Bar)
(*y).thingOne = "hello"
(*y).thingTwo = 1
// not OK:
z := make(Bar) // compile error: cannot make type Bar
z.thingOne = "hello"
z.thingTwo = 1
// OK:
x := make(Foo)
x["x"] = "goodbye"
x["y"] = "world"
// not OK:
u := new(Foo)
(*u)["x"] = "goodbye" // !! panic !!: runtime error: assignment to entry in nil map
(*u)["y"] = "world"
}
// annoy1.go
package main
type Foo map[string]string
type Bar struct {
thingOne string
thingTwo int
}
func main() {
// OK:
y := new(Bar)
(*y).thingOne = "hello"
(*y).thingTwo = 1
// not OK:
z := make(Bar) // compile error: cannot make type Bar
z.thingOne = "hello"
z.thingTwo = 1
// OK:
x := make(Foo)
x["x"] = "goodbye"
x["y"] = "world"
// not OK:
u := new(Foo)
(*u)["x"] = "goodbye" // !! panic !!: runtime error: assignment to entry in nil map
(*u)["y"] = "world"
}

83
eBook/examples/chapter_10/person.go
View File

@@ -1,41 +1,42 @@
package main
import (
"fmt"
"strings"
)
type Person struct {
firstName string
lastName string
}
func upPerson (p *Person) {
p.firstName = strings.ToUpper(p.firstName)
p.lastName = strings.ToUpper(p.lastName)
}
func main() {
// 1- struct as a value type:
var pers1 Person
pers1.firstName = "Chris"
pers1.lastName = "Woodward"
upPerson(&pers1)
fmt.Printf("The name of the person is %s %s\n", pers1.firstName, pers1.lastName)
// 2 - struct as a pointer:
pers2 := new(Person)
pers2.firstName = "Chris"
pers2.lastName = "Woodward"
(*pers2).lastName = "Woodward"
upPerson(pers2)
fmt.Printf("The name of the person is %s %s\n", pers2.firstName, pers2.lastName)
// 3 - struct as a literal:
pers3 := &Person{"Chris","Woodward"}
upPerson(pers3)
fmt.Printf("The name of the person is %s %s\n", pers3.firstName, pers3.lastName)
}
/* Output:
The name of the person is CHRIS WOODWARD
The name of the person is CHRIS WOODWARD
The name of the person is CHRIS WOODWARD
*/
package main
import (
"fmt"
"strings"
)
type Person struct {
firstName string
lastName string
}
func upPerson(p *Person) {
p.firstName = strings.ToUpper(p.firstName)
p.lastName = strings.ToUpper(p.lastName)
}
func main() {
// 1- struct as a value type:
var pers1 Person
pers1.firstName = "Chris"
pers1.lastName = "Woodward"
upPerson(&pers1)
fmt.Printf("The name of the person is %s %s\n", pers1.firstName, pers1.lastName)
// 2 - struct as a pointer:
pers2 := new(Person)
pers2.firstName = "Chris"
pers2.lastName = "Woodward"
(*pers2).lastName = "Woodward"
upPerson(pers2)
fmt.Printf("The name of the person is %s %s\n", pers2.firstName, pers2.lastName)
// 3 - struct as a literal:
pers3 := &Person{"Chris", "Woodward"}
upPerson(pers3)
fmt.Printf("The name of the person is %s %s\n", pers3.firstName, pers3.lastName)
}
/* Output:
The name of the person is CHRIS WOODWARD
The name of the person is CHRIS WOODWARD
The name of the person is CHRIS WOODWARD
*/

31
eBook/examples/chapter_10/person2.go
View File

@@ -1,17 +1,14 @@
package person
type Person struct {
firstName string
lastName string
}
func (p *Person) FirstName() string {
return p.firstName
}
func (p *Person) SetFirstName(newName string) {
p.firstName = newName
}
package person
type Person struct {
firstName string
lastName string
}
func (p *Person) FirstName() string {
return p.firstName
}
func (p *Person) SetFirstName(newName string) {
p.firstName = newName
}

57
eBook/examples/chapter_10/pointer_value.go
View File

@@ -1,28 +1,29 @@
// pointer_value.go
package main
import (
"fmt"
)
type B struct {
thing int
}
func (b *B) change() { b.thing = 1 }
func (b B) write() string { return fmt.Sprint(b) }
func main() {
var b1 B // b1 is value
b1.change()
fmt.Println(b1.write())
b2 := new(B) // b2 is pointer
b2.change()
fmt.Println(b2.write())
}
/* Output:
{1}
{1}
*/
// pointer_value.go
package main
import (
"fmt"
)
type B struct {
thing int
}
func (b *B) change() { b.thing = 1 }
func (b B) write() string { return fmt.Sprint(b) }
func main() {
var b1 B // b1 is value
b1.change()
fmt.Println(b1.write())
b2 := new(B) // b2 is pointer
b2.change()
fmt.Println(b2.write())
}
/* Output:
{1}
{1}
*/

49
eBook/examples/chapter_10/struct_conversions.go
View File

@@ -1,24 +1,25 @@
// struct_conversions.go
package main
import (
"fmt"
)
type number struct {
f float32
}
type nr number // alias type
func main() {
a := number{5.0}
b := nr{5.0}
// var i float32 = b // compile-error: cannot use b (type nr) as type float32 in assignment
// var i = float32(b) // compile-error: cannot convert b (type nr) to type float32
// var c number = b // compile-error: cannot use b (type nr) as type number in assignment
// needs a conversion:
var c = number(b)
fmt.Println(a, b, c)
}
// output: {5} {5} {5}
// struct_conversions.go
package main
import (
"fmt"
)
type number struct {
f float32
}
type nr number // alias type
func main() {
a := number{5.0}
b := nr{5.0}
// var i float32 = b // compile-error: cannot use b (type nr) as type float32 in assignment
// var i = float32(b) // compile-error: cannot convert b (type nr) to type float32
// var c number = b // compile-error: cannot use b (type nr) as type number in assignment
// needs a conversion:
var c = number(b)
fmt.Println(a, b, c)
}
// output: {5} {5} {5}

12
eBook/examples/chapter_10/struct_pack/structPack.go
View File

@@ -1,6 +1,6 @@
package structPack
type ExpStruct struct {
Mi1 int
Mf1 float32
}
package structPack
type ExpStruct struct {
Mi1 int
Mf1 float32
}

61
eBook/examples/chapter_10/struct_tag.go
View File

@@ -1,30 +1,31 @@
package main
import (
"fmt"
"reflect"
)
type TagType struct { // tags
field1 bool "An important answer"
field2 string "The name of the thing"
field3 int "How much there are"
}
func main() {
tt := TagType{true, "Barak Obama", 1}
for i:= 0; i < 3; i++ {
refTag(tt, i)
}
}
func refTag(tt TagType, ix int) {
ttType := reflect.TypeOf(tt)
ixField := ttType.Field(ix)
fmt.Printf("%v\n", ixField.Tag)
}
/* Output:
An important answer
The name of the thing
How much there are
*/
package main
import (
"fmt"
"reflect"
)
type TagType struct { // tags
field1 bool "An important answer"
field2 string "The name of the thing"
field3 int "How much there are"
}
func main() {
tt := TagType{true, "Barak Obama", 1}
for i := 0; i < 3; i++ {
refTag(tt, i)
}
}
func refTag(tt TagType, ix int) {
ttType := reflect.TypeOf(tt)
ixField := ttType.Field(ix)
fmt.Printf("%v\n", ixField.Tag)
}
/* Output:
An important answer
The name of the thing
How much there are
*/

68
eBook/examples/chapter_10/structs_anonymous_fields.go
View File

@@ -1,34 +1,34 @@
package main
import "fmt"
type innerS struct {
in1 int
in2 int
}
type outerS struct {
b int
c float32
int // anonymous field
innerS // anonymous field
}
func main() {
outer := new(outerS)
outer.b = 6
outer.c = 7.5
outer.int = 60
outer.in1 = 5
outer.in2 = 10
fmt.Printf("outer.b is: %d\n", outer.b)
fmt.Printf("outer.c is: %f\n", outer.c)
fmt.Printf("outer.int is: %d\n", outer.int)
fmt.Printf("outer.in1 is: %d\n", outer.in1)
fmt.Printf("outer.in2 is: %d\n", outer.in2)
// with a struct-literal:
outer2 := outerS{6, 7.5, 60, innerS{5, 10}}
fmt.Println("outer2 is: ", outer2)
}
package main
import "fmt"
type innerS struct {
in1 int
in2 int
}
type outerS struct {
b int
c float32
int // anonymous field
innerS // anonymous field
}
func main() {
outer := new(outerS)
outer.b = 6
outer.c = 7.5
outer.int = 60
outer.in1 = 5
outer.in2 = 10
fmt.Printf("outer.b is: %d\n", outer.b)
fmt.Printf("outer.c is: %f\n", outer.c)
fmt.Printf("outer.int is: %d\n", outer.int)
fmt.Printf("outer.in1 is: %d\n", outer.in1)
fmt.Printf("outer.in2 is: %d\n", outer.in2)
// with a struct-literal:
outer2 := outerS{6, 7.5, 60, innerS{5, 10}}
fmt.Println("outer2 is: ", outer2)
}

46
eBook/examples/chapter_10/structs_fields.go
View File

@@ -1,23 +1,23 @@
package main
import "fmt"
type struct1 struct {
i1 int
f1 float32
str string
}
func main() {
// var ms *struct1 = new(struct1)
// better:
ms := new(struct1)
ms.i1 = 10
ms.f1 = 15.5
ms.str = "Chris"
// ms := &struct1{10, 15.5, "Chris"}
fmt.Printf("The int is: %d\n", ms.i1)
fmt.Printf("The float is: %f\n", ms.f1)
fmt.Printf("The string is: %s\n", ms.str)
fmt.Println(ms) // output: &{10 15.5 Chris}
}
package main
import "fmt"
type struct1 struct {
i1 int
f1 float32
str string
}
func main() {
// var ms *struct1 = new(struct1)
// better:
ms := new(struct1)
ms.i1 = 10
ms.f1 = 15.5
ms.str = "Chris"
// ms := &struct1{10, 15.5, "Chris"}
fmt.Printf("The int is: %d\n", ms.i1)
fmt.Printf("The float is: %f\n", ms.f1)
fmt.Printf("The string is: %s\n", ms.str)
fmt.Println(ms) // output: &{10 15.5 Chris}
}

28
eBook/examples/chapter_10/use_person2.go
View File

@@ -1,14 +1,14 @@
package main
import (
"fmt"
"./person"
)
func main() {
p := new(person.Person)
// error: p.firstName undefined (cannot refer to unexported field or method firstName)
// p.firstName = "Eric"
p.SetFirstName("Eric")
fmt.Println(p.FirstName()) // Output: Eric
}
package main
import (
"./person"
"fmt"
)
func main() {
p := new(person.Person)
// error: p.firstName undefined (cannot refer to unexported field or method firstName)
// p.firstName = "Eric"
p.SetFirstName("Eric")
fmt.Println(p.FirstName()) // Output: Eric
}

189
eBook/examples/chapter_11/cars.go
View File

@@ -1,95 +1,94 @@
// cars.go
package main
import (
"fmt"
)
type Any interface{}
type Car struct {
Model string
Manufacturer string
BuildYear int
// ...
}
type Cars []*Car
func main() {
// make some cars:
ford := &Car{"Fiesta","Ford", 2008}
bmw := &Car{"XL 450", "BMW", 2011}
merc := &Car{"D600", "Mercedes", 2009}
bmw2 := &Car{"X 800", "BMW", 2008}
// query:
allCars := Cars([]*Car{ford, bmw, merc, bmw2})
allNewBMWs := allCars.FindAll(func(car *Car) bool {
return (car.Manufacturer == "BMW") && (car.BuildYear > 2010)
})
fmt.Println("AllCars: ", allCars)
fmt.Println("New BMWs: ", allNewBMWs)
//
manufacturers := []string{"Ford", "Aston Martin", "Land Rover", "BMW", "Jaguar"}
sortedAppender, sortedCars := MakeSortedAppender(manufacturers)
allCars.Process(sortedAppender)
fmt.Println("Map sortedCars: ", sortedCars)
BMWCount := len(sortedCars["BMW"])
fmt.Println("We have ", BMWCount, " BMWs")
}
// Process all cars with the given function f:
func (cs Cars) Process(f func(car *Car)) {
for _, c := range cs {
f(c)
}
}
// Find all cars matching a given criteria.
func (cs Cars) FindAll(f func(car *Car) bool) Cars {
cars := make([]*Car, 0)
cs.Process(func(c *Car) {
if f(c) {
cars = append(cars, c)
}
})
return cars
}
// Process cars and create new data.
func (cs Cars) Map(f func(car *Car) Any) []Any {
result := make([]Any, 0)
ix := 0
cs.Process(func(c *Car) {
result[ix] = f(c)
ix++
})
return result
}
func MakeSortedAppender(manufacturers []string) (func(car *Car), map[string]Cars) {
// Prepare maps of sorted cars.
sortedCars := make(map[string]Cars)
for _, m := range manufacturers {
sortedCars[m] = make([]*Car, 0)
}
sortedCars["Default"] = make([]*Car, 0)
// Prepare appender function:
appender := func(c *Car) {
if _, ok := sortedCars[c.Manufacturer]; ok {
sortedCars[c.Manufacturer] = append(sortedCars[c.Manufacturer], c)
} else {
sortedCars["Default"] = append(sortedCars["Default"], c)
}
}
return appender, sortedCars
}
/* Output:
AllCars: [0xf8400038a0 0xf840003bd0 0xf840003ba0 0xf840003b70]
New BMWs: [0xf840003bd0]
Map sortedCars: map[Default:[0xf840003ba0] Jaguar:[] Land Rover:[] BMW:[0xf840003bd0 0xf840003b70] Aston Martin:[] Ford:[0xf8400038a0]]
We have 2 BMWs
*/
// cars.go
package main
import (
"fmt"
)
type Any interface{}
type Car struct {
Model string
Manufacturer string
BuildYear int
// ...
}
type Cars []*Car
func main() {
// make some cars:
ford := &Car{"Fiesta", "Ford", 2008}
bmw := &Car{"XL 450", "BMW", 2011}
merc := &Car{"D600", "Mercedes", 2009}
bmw2 := &Car{"X 800", "BMW", 2008}
// query:
allCars := Cars([]*Car{ford, bmw, merc, bmw2})
allNewBMWs := allCars.FindAll(func(car *Car) bool {
return (car.Manufacturer == "BMW") && (car.BuildYear > 2010)
})
fmt.Println("AllCars: ", allCars)
fmt.Println("New BMWs: ", allNewBMWs)
//
manufacturers := []string{"Ford", "Aston Martin", "Land Rover", "BMW", "Jaguar"}
sortedAppender, sortedCars := MakeSortedAppender(manufacturers)
allCars.Process(sortedAppender)
fmt.Println("Map sortedCars: ", sortedCars)
BMWCount := len(sortedCars["BMW"])
fmt.Println("We have ", BMWCount, " BMWs")
}
// Process all cars with the given function f:
func (cs Cars) Process(f func(car *Car)) {
for _, c := range cs {
f(c)
}
}
// Find all cars matching a given criteria.
func (cs Cars) FindAll(f func(car *Car) bool) Cars {
cars := make([]*Car, 0)
cs.Process(func(c *Car) {
if f(c) {
cars = append(cars, c)
}
})
return cars
}
// Process cars and create new data.
func (cs Cars) Map(f func(car *Car) Any) []Any {
result := make([]Any, 0)
ix := 0
cs.Process(func(c *Car) {
result[ix] = f(c)
ix++
})
return result
}
func MakeSortedAppender(manufacturers []string) (func(car *Car), map[string]Cars) {
// Prepare maps of sorted cars.
sortedCars := make(map[string]Cars)
for _, m := range manufacturers {
sortedCars[m] = make([]*Car, 0)
}
sortedCars["Default"] = make([]*Car, 0)
// Prepare appender function:
appender := func(c *Car) {
if _, ok := sortedCars[c.Manufacturer]; ok {
sortedCars[c.Manufacturer] = append(sortedCars[c.Manufacturer], c)
} else {
sortedCars["Default"] = append(sortedCars["Default"], c)
}
}
return appender, sortedCars
}
/* Output:
AllCars: [0xf8400038a0 0xf840003bd0 0xf840003ba0 0xf840003b70]
New BMWs: [0xf840003bd0]
Map sortedCars: map[Default:[0xf840003ba0] Jaguar:[] Land Rover:[] BMW:[0xf840003bd0 0xf840003b70] Aston Martin:[] Ford:[0xf8400038a0]]
We have 2 BMWs
*/

64
eBook/examples/chapter_11/duck_dance.go
View File

@@ -1,32 +1,32 @@
package main
import "fmt"
type IDuck interface {
Quack()
Walk()
}
func DuckDance(duck IDuck) {
for i := 1; i <= 3; i++ {
duck.Quack()
duck.Walk()
}
}
type Bird struct {
// ...
}
func (b *Bird) Quack() {
fmt.Println("I am quacking!")
}
func (b *Bird) Walk() {
fmt.Println("I am walking!")
}
func main() {
b := new(Bird)
DuckDance(b)
}
package main
import "fmt"
type IDuck interface {
Quack()
Walk()
}
func DuckDance(duck IDuck) {
for i := 1; i <= 3; i++ {
duck.Quack()
duck.Walk()
}
}
type Bird struct {
// ...
}
func (b *Bird) Quack() {
fmt.Println("I am quacking!")
}
func (b *Bird) Walk() {
fmt.Println("I am walking!")
}
func main() {
b := new(Bird)
DuckDance(b)
}

76
eBook/examples/chapter_11/empty_interface.go
View File

@@ -1,38 +1,38 @@
package main
import "fmt"
var i = 5
var str = "ABC"
type Person struct {
name string
age int
}
type Any interface{}
func main() {
var val Any
val = 5
fmt.Printf("val has the value: %v\n", val)
val = str
fmt.Printf("val has the value: %v\n", val)
pers1 := new(Person)
pers1.name = "Rob Pike"
pers1.age = 55
val = pers1
fmt.Printf("val has the value: %v\n", val)
switch t := val.(type) {
case int:
fmt.Printf("Type int %T\n", t)
case string:
fmt.Printf("Type string %T\n", t)
case bool:
fmt.Printf("Type boolean %T\n", t)
case *Person:
fmt.Printf("Type pointer to Person %T\n", *t)
default:
fmt.Printf("Unexpected type %T", t)
}
}
package main
import "fmt"
var i = 5
var str = "ABC"
type Person struct {
name string
age int
}
type Any interface{}
func main() {
var val Any
val = 5
fmt.Printf("val has the value: %v\n", val)
val = str
fmt.Printf("val has the value: %v\n", val)
pers1 := new(Person)
pers1.name = "Rob Pike"
pers1.age = 55
val = pers1
fmt.Printf("val has the value: %v\n", val)
switch t := val.(type) {
case int:
fmt.Printf("Type int %T\n", t)
case string:
fmt.Printf("Type string %T\n", t)
case bool:
fmt.Printf("Type boolean %T\n", t)
case *Person:
fmt.Printf("Type pointer to Person %T\n", *t)
default:
fmt.Printf("Unexpected type %T", t)
}
}

1
eBook/examples/chapter_11/emptyint_switch.go
View File

@@ -29,4 +29,5 @@ func TypeSwitch() {
func main() {
TypeSwitch()
}
// Output: any hello is a special String!

61
eBook/examples/chapter_11/interfaces.go
View File

@@ -1,30 +1,31 @@
package main
import "fmt"
type Shaper interface {
Area() float32
// Perimeter() float32
}
type Square struct {
side float32
}
func (sq *Square) Area() float32 {
return sq.side * sq.side
}
func main() {
sq1 := new(Square)
sq1.side = 5
// var areaIntf Shaper
// areaIntf = sq1
// shorter, without separate declaration:
// areaIntf := Shaper(sq1)
// or even:
areaIntf := sq1
fmt.Printf("The square has area: %f\n", areaIntf.Area())
}
// The square has area: 25.000000
package main
import "fmt"
type Shaper interface {
Area() float32
// Perimeter() float32
}
type Square struct {
side float32
}
func (sq *Square) Area() float32 {
return sq.side * sq.side
}
func main() {
sq1 := new(Square)
sq1.side = 5
// var areaIntf Shaper
// areaIntf = sq1
// shorter, without separate declaration:
// areaIntf := Shaper(sq1)
// or even:
areaIntf := sq1
fmt.Printf("The square has area: %f\n", areaIntf.Area())
}
// The square has area: 25.000000

88
eBook/examples/chapter_11/interfaces_poly.go
View File

@@ -1,45 +1,43 @@
// interfaces_poly.go
package main
import "fmt"
type Shaper interface {
Area() float32
}
type Square struct {
side float32
}
func (sq *Square) Area() float32 {
return sq.side * sq.side
}
type Rectangle struct {
length, width float32
}
func (r Rectangle) Area() float32 {
return r.length * r.width
}
func main() {
r := Rectangle{5, 3} // Area() of Rectangle needs a value
q := &Square{5} // Area() of Square needs a pointer
shapes := []Shaper{r, q}
fmt.Println("Looping through shapes for area ...")
for n, _ := range shapes {
fmt.Println("Shape details: ", shapes[n])
fmt.Println("Area of this shape is: ", shapes[n].Area())
}
}
/* Output:
Looping through shapes for area ...
Shape details: {5 3}
Area of this shape is: 15
Shape details: &{5}
Area of this shape is: 25
*/
// interfaces_poly.go
package main
import "fmt"
type Shaper interface {
Area() float32
}
type Square struct {
side float32
}
func (sq *Square) Area() float32 {
return sq.side * sq.side
}
type Rectangle struct {
length, width float32
}
func (r Rectangle) Area() float32 {
return r.length * r.width
}
func main() {
r := Rectangle{5, 3} // Area() of Rectangle needs a value
q := &Square{5} // Area() of Square needs a pointer
shapes := []Shaper{r, q}
fmt.Println("Looping through shapes for area ...")
for n := range shapes {
fmt.Println("Shape details: ", shapes[n])
fmt.Println("Area of this shape is: ", shapes[n].Area())
}
}
/* Output:
Looping through shapes for area ...
Shape details: {5 3}
Area of this shape is: 15
Shape details: &{5}
Area of this shape is: 25
*/

97
eBook/examples/chapter_11/methodset2.go
View File

@@ -1,48 +1,49 @@
// methodset2.go
package main
import (
"fmt"
)
type List []int
func (l List) Len() int { return len(l) }
func (l *List) Append(val int) { *l = append(*l, val) }
type Appender interface {
Append(int)
}
func CountInto(a Appender, start, end int) {
for i := start; i <= end; i++ {
a.Append(i)
}
}
type Lener interface {
Len() int
}
func LongEnough(l Lener) bool {
return l.Len()*10 > 42
}
func main() {
// A bare value
var lst List
// compiler error:
// cannot use lst (type List) as type Appender in function argument:
// List does not implement Appender (Append method requires pointer receiver)
// CountInto(lst, 1, 10) // INVALID: Append has a pointer receiver
if LongEnough(lst) { // VALID: Identical receiver type
fmt.Printf(" - lst is long enough")
}
// A pointer value
plst := new(List)
CountInto(plst, 1, 10) // VALID: Identical receiver type
if LongEnough(plst) { // VALID: a *List can be dereferenced for the receiver
fmt.Printf(" - plst is long enough") // - plst is long enoug
}
}
// methodset2.go
package main
import (
"fmt"
)
type List []int
func (l List) Len() int { return len(l) }
func (l *List) Append(val int) { *l = append(*l, val) }
type Appender interface {
Append(int)
}
func CountInto(a Appender, start, end int) {
for i := start; i <= end; i++ {
a.Append(i)
}
}
type Lener interface {
Len() int
}
func LongEnough(l Lener) bool {
return l.Len()*10 > 42
}
func main() {
// A bare value
var lst List
// compiler error:
// cannot use lst (type List) as type Appender in function argument:
// List does not implement Appender (Append method requires pointer receiver)
// CountInto(lst, 1, 10) // INVALID: Append has a pointer receiver
if LongEnough(lst) { // VALID: Identical receiver type
fmt.Printf(" - lst is long enough")
}
// A pointer value
plst := new(List)
CountInto(plst, 1, 10) // VALID: Identical receiver type
if LongEnough(plst) { // VALID: a *List can be dereferenced for the receiver
fmt.Printf(" - plst is long enough") // - plst is long enoug
}
}

131
eBook/examples/chapter_11/multi_interfaces_poly.go
View File

@@ -1,65 +1,66 @@
//multi_interfaces_poly.go
package main
import "fmt"
type Shaper interface {
Area() float32
}
type TopologicalGenus interface {
Rank() int
}
type Square struct {
side float32
}
func (sq *Square) Area() float32 {
return sq.side * sq.side
}
func (sq *Square) Rank() int {
return 1
}
type Rectangle struct {
length, width float32
}
func (r Rectangle) Area() float32 {
return r.length * r.width
}
func (r Rectangle) Rank() int {
return 2
}
func main() {
r := Rectangle{5, 3} // Area() of Rectangle needs a value
q := &Square{5} // Area() of Square needs a pointer
shapes := []Shaper{r, q}
fmt.Println("Looping through shapes for area ...")
for n, _ := range shapes {
fmt.Println("Shape details: ", shapes[n])
fmt.Println("Area of this shape is: ", shapes[n].Area())
}
topgen := []TopologicalGenus{r, q}
fmt.Println("Looping through topgen for rank ...")
for n, _ := range topgen {
fmt.Println("Shape details: ", topgen[n])
fmt.Println("Topological Genus of this shape is: ", topgen[n].Rank())
}
}
/* Output:
Looping through shapes for area ...
Shape details: {5 3}
Area of this shape is: 15
Shape details: &{5}
Area of this shape is: 25
Looping through topgen for rank ...
Shape details: {5 3}
Topological Genus of this shape is: 2
Shape details: &{5}
Topological Genus of this shape is: 1
*/
//multi_interfaces_poly.go
package main
import "fmt"
type Shaper interface {
Area() float32
}
type TopologicalGenus interface {
Rank() int
}
type Square struct {
side float32
}
func (sq *Square) Area() float32 {
return sq.side * sq.side
}
func (sq *Square) Rank() int {
return 1
}
type Rectangle struct {
length, width float32
}
func (r Rectangle) Area() float32 {
return r.length * r.width
}
func (r Rectangle) Rank() int {
return 2
}
func main() {
r := Rectangle{5, 3} // Area() of Rectangle needs a value
q := &Square{5} // Area() of Square needs a pointer
shapes := []Shaper{r, q}
fmt.Println("Looping through shapes for area ...")
for n := range shapes {
fmt.Println("Shape details: ", shapes[n])
fmt.Println("Area of this shape is: ", shapes[n].Area())
}
topgen := []TopologicalGenus{r, q}
fmt.Println("Looping through topgen for rank ...")
for n := range topgen {
fmt.Println("Shape details: ", topgen[n])
fmt.Println("Topological Genus of this shape is: ", topgen[n].Rank())
}
}
/* Output:
Looping through shapes for area ...
Shape details: {5 3}
Area of this shape is: 15
Shape details: &{5}
Area of this shape is: 25
Looping through topgen for rank ...
Shape details: {5 3}
Topological Genus of this shape is: 2
Shape details: &{5}
Topological Genus of this shape is: 1
*/

62
eBook/examples/chapter_11/node_structures.go
View File

@@ -1,31 +1,31 @@
// node_structures.go
package main
import "fmt"
type Node struct {
le *Node
data interface{}
ri *Node
}
func NewNode(left, right *Node) *Node {
return &Node{left, nil, right}
}
func (n *Node) SetData(data interface{}) {
n.data = data
}
func main() {
root := NewNode(nil,nil)
root.SetData("root node")
// make child (leaf) nodes:
a := NewNode(nil,nil)
a.SetData("left node")
b := NewNode(nil,nil)
b.SetData("right node")
root.le = a
root.ri = b
fmt.Printf("%v\n", root) // Output: &{0x125275f0 root node 0x125275e0}
}
// node_structures.go
package main
import "fmt"
type Node struct {
le *Node
data interface{}
ri *Node
}
func NewNode(left, right *Node) *Node {
return &Node{left, nil, right}
}
func (n *Node) SetData(data interface{}) {
n.data = data
}
func main() {
root := NewNode(nil, nil)
root.SetData("root node")
// make child (leaf) nodes:
a := NewNode(nil, nil)
a.SetData("left node")
b := NewNode(nil, nil)
b.SetData("right node")
root.le = a
root.ri = b
fmt.Printf("%v\n", root) // Output: &{0x125275f0 root node 0x125275e0}
}

93
eBook/examples/chapter_11/print.go
View File

@@ -1,43 +1,50 @@
// print.go
package main
import (
"os"
"strconv"
)
type Stringer interface {
String() string
}
type Celsius float64
func (c Celsius) String() string {
return strconv.FormatFloat(float64(c),'f', 1, 64) + " °C"
}
type Day int
var dayName = []string{"Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"}
func (day Day) String() string {
return dayName[day]
}
func print(args ...interface{}) {
for i, arg := range args {
if i > 0 {os.Stdout.WriteString(" ")}
switch a := arg.(type) { // type switch
case Stringer: os.Stdout.WriteString(a.String())
case int: os.Stdout.WriteString(strconv.Itoa(a))
case string: os.Stdout.WriteString(a)
// more types
default: os.Stdout.WriteString("???")
}
}
}
func main() {
print(Day(1), "was", Celsius(18.36)) // Tuesday was 18.4 °C
}
// Tuesday was 18.4 °C
// print.go
package main
import (
"os"
"strconv"
)
type Stringer interface {
String() string
}
type Celsius float64
func (c Celsius) String() string {
return strconv.FormatFloat(float64(c), 'f', 1, 64) + " °C"
}
type Day int
var dayName = []string{"Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"}
func (day Day) String() string {
return dayName[day]
}
func print(args ...interface{}) {
for i, arg := range args {
if i > 0 {
os.Stdout.WriteString(" ")
}
switch a := arg.(type) { // type switch
case Stringer:
os.Stdout.WriteString(a.String())
case int:
os.Stdout.WriteString(strconv.Itoa(a))
case string:
os.Stdout.WriteString(a)
// more types
default:
os.Stdout.WriteString("???")
}
}
}
func main() {
print(Day(1), "was", Celsius(18.36)) // Tuesday was 18.4 °C
}
// Tuesday was 18.4 °C

65
eBook/examples/chapter_11/reflect1.go
View File

@@ -1,32 +1,33 @@
// reflect1.go
// blog: Laws of Reflection
package main
import (
"fmt"
"reflect"
)
func main() {
var x float64 = 3.4
fmt.Println("type:", reflect.TypeOf(x))
v := reflect.ValueOf(x)
fmt.Println("value:", v)
fmt.Println("type:", v.Type())
fmt.Println("kind:", v.Kind())
fmt.Println("value:", v.Float())
fmt.Println(v.Interface())
fmt.Printf("value is %5.2e\n", v.Interface())
y := v.Interface().(float64)
fmt.Println(y)
}
/* output:
type: float64
value: <float64 Value>
type: float64
kind: float64
value: 3.4
3.4
value is 3.40e+00
3.4
*/
// reflect1.go
// blog: Laws of Reflection
package main
import (
"fmt"
"reflect"
)
func main() {
var x float64 = 3.4
fmt.Println("type:", reflect.TypeOf(x))
v := reflect.ValueOf(x)
fmt.Println("value:", v)
fmt.Println("type:", v.Type())
fmt.Println("kind:", v.Kind())
fmt.Println("value:", v.Float())
fmt.Println(v.Interface())
fmt.Printf("value is %5.2e\n", v.Interface())
y := v.Interface().(float64)
fmt.Println(y)
}
/* output:
type: float64
value: <float64 Value>
type: float64
kind: float64
value: 3.4
3.4
value is 3.40e+00
3.4
*/

67
eBook/examples/chapter_11/reflect2.go
View File

@@ -1,33 +1,34 @@
// reflect2.go
package main
import (
"fmt"
"reflect"
)
func main() {
var x float64 = 3.4
v := reflect.ValueOf(x)
// setting a value:
// v.SetFloat(3.1415) // Error: will panic: reflect.Value.SetFloat using unaddressable value
fmt.Println("settability of v:", v.CanSet())
v = reflect.ValueOf(&x) // Note: take the address of x.
fmt.Println("type of v:", v.Type())
fmt.Println("settability of v:", v.CanSet())
v = v.Elem()
fmt.Println("The Elem of v is: ", v)
fmt.Println("settability of v:", v.CanSet())
v.SetFloat(3.1415) // this works!
fmt.Println(v.Interface())
fmt.Println(v)
}
/* Output:
settability of v: false
type of v: *float64
settability of v: false
The Elem of v is: <float64 Value>
settability of v: true
3.1415
<float64 Value>
*/
// reflect2.go
package main
import (
"fmt"
"reflect"
)
func main() {
var x float64 = 3.4
v := reflect.ValueOf(x)
// setting a value:
// v.SetFloat(3.1415) // Error: will panic: reflect.Value.SetFloat using unaddressable value
fmt.Println("settability of v:", v.CanSet())
v = reflect.ValueOf(&x) // Note: take the address of x.
fmt.Println("type of v:", v.Type())
fmt.Println("settability of v:", v.CanSet())
v = v.Elem()
fmt.Println("The Elem of v is: ", v)
fmt.Println("settability of v:", v.CanSet())
v.SetFloat(3.1415) // this works!
fmt.Println(v.Interface())
fmt.Println(v)
}
/* Output:
settability of v: false
type of v: *float64
settability of v: false
The Elem of v is: <float64 Value>
settability of v: true
3.1415
<float64 Value>
*/

95
eBook/examples/chapter_11/reflect_struct.go
View File

@@ -1,47 +1,48 @@
// reflect.go
package main
import (
"fmt"
"reflect"
)
type NotknownType struct {
s1, s2, s3 string
}
func (n NotknownType) String() string {
return n.s1 + " - " + n.s2 + " - " + n.s3
}
// variable to investigate:
var secret interface {} = NotknownType{"Ada", "Go", "Oberon"}
func main() {
value := reflect.ValueOf(secret) // <main.NotknownType Value>
typ := reflect.TypeOf(secret) // main.NotknownType
// alternative:
//typ := value.Type() // main.NotknownType
fmt.Println(typ)
knd := value.Kind() // struct
fmt.Println(knd)
// iterate through the fields of the struct:
for i:= 0; i < value.NumField(); i++ {
fmt.Printf("Field %d: %v\n", i, value.Field(i))
// error: panic: reflect.Value.SetString using value obtained using unexported field
//value.Field(i).SetString("C#")
}
// call the first method, which is String():
results := value.Method(0).Call(nil)
fmt.Println(results) // [Ada - Go - Oberon]
}
/* Output:
main.NotknownType
struct
Field 0: Ada
Field 1: Go
Field 2: Oberon
[Ada - Go - Oberon]
*/
// reflect.go
package main
import (
"fmt"
"reflect"
)
type NotknownType struct {
s1, s2, s3 string
}
func (n NotknownType) String() string {
return n.s1 + " - " + n.s2 + " - " + n.s3
}
// variable to investigate:
var secret interface{} = NotknownType{"Ada", "Go", "Oberon"}
func main() {
value := reflect.ValueOf(secret) // <main.NotknownType Value>
typ := reflect.TypeOf(secret) // main.NotknownType
// alternative:
//typ := value.Type() // main.NotknownType
fmt.Println(typ)
knd := value.Kind() // struct
fmt.Println(knd)
// iterate through the fields of the struct:
for i := 0; i < value.NumField(); i++ {
fmt.Printf("Field %d: %v\n", i, value.Field(i))
// error: panic: reflect.Value.SetString using value obtained using unexported field
//value.Field(i).SetString("C#")
}
// call the first method, which is String():
results := value.Method(0).Call(nil)
fmt.Println(results) // [Ada - Go - Oberon]
}
/* Output:
main.NotknownType
struct
Field 0: Ada
Field 1: Go
Field 2: Oberon
[Ada - Go - Oberon]
*/

63
eBook/examples/chapter_11/reflect_struct2.go
View File

@@ -1,31 +1,32 @@
// reflect_struct2.go
package main
import (
"fmt"
"reflect"
)
type T struct {
A int
B string
}
func main() {
t := T{23, "skidoo"}
s := reflect.ValueOf(&t).Elem()
typeOfT := s.Type()
for i := 0; i < s.NumField(); i++ {
f := s.Field(i)
fmt.Printf("%d: %s %s = %v\n", i,
typeOfT.Field(i).Name, f.Type(), f.Interface())
}
s.Field(0).SetInt(77)
s.Field(1).SetString("Sunset Strip")
fmt.Println("t is now", t)
}
/* Output:
0: A int = 23
1: B string = skidoo
t is now {77 Sunset Strip}
*/
// reflect_struct2.go
package main
import (
"fmt"
"reflect"
)
type T struct {
A int
B string
}
func main() {
t := T{23, "skidoo"}
s := reflect.ValueOf(&t).Elem()
typeOfT := s.Type()
for i := 0; i < s.NumField(); i++ {
f := s.Field(i)
fmt.Printf("%d: %s %s = %v\n", i,
typeOfT.Field(i).Name, f.Type(), f.Interface())
}
s.Field(0).SetInt(77)
s.Field(1).SetString("Sunset Strip")
fmt.Println("t is now", t)
}
/* Output:
0: A int = 23
1: B string = skidoo
t is now {77 Sunset Strip}
*/

118
eBook/examples/chapter_11/sort/sort.go
View File

@@ -1,58 +1,60 @@
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Sorting using a general interface
package sort
// Sorting interface
type Interface interface {
Len() int
Less(i, j int) bool
Swap(i, j int)
}
// General sort function
func Sort(data Interface) {
for i := 1; i < data.Len(); i++ {
for j := i; j > 0 && data.Less(j, j-1); j-- {
data.Swap(j, j-1)
}
}
}
// Test if data is sorted
func IsSorted(data Interface) bool {
n := data.Len()
for i := n - 1; i > 0; i-- {
if data.Less(i, i-1) {
return false
}
}
return true
}
// Convenience types for common cases: IntArray
type IntArray []int
func (p IntArray) Len() int { return len(p) }
func (p IntArray) Less(i, j int) bool { return p[i] < p[j] }
func (p IntArray) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
type Float64Array []float64
func (p Float64Array) Len() int { return len(p) }
func (p Float64Array) Less(i, j int) bool { return p[i] < p[j] }
func (p Float64Array) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
type StringArray []string
func (p StringArray) Len() int { return len(p) }
func (p StringArray) Less(i, j int) bool { return p[i] < p[j] }
func (p StringArray) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
// Convenience wrappers for common cases
func SortInts(a []int) { Sort(IntArray(a)) }
func SortFloat64s(a []float64) { Sort(Float64Array(a)) }
func SortStrings(a []string) { Sort(StringArray(a)) }
func IntsAreSorted(a []int) bool { return IsSorted(IntArray(a)) }
func Float64sAreSorted(a []float64) bool { return IsSorted(Float64Array(a)) }
func StringsAreSorted(a []string) bool { return IsSorted(StringArray(a)) }
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Sorting using a general interface
package sort
// Sorting interface
type Interface interface {
Len() int
Less(i, j int) bool
Swap(i, j int)
}
// General sort function
func Sort(data Interface) {
for i := 1; i < data.Len(); i++ {
for j := i; j > 0 && data.Less(j, j-1); j-- {
data.Swap(j, j-1)
}
}
}
// Test if data is sorted
func IsSorted(data Interface) bool {
n := data.Len()
for i := n - 1; i > 0; i-- {
if data.Less(i, i-1) {
return false
}
}
return true
}
// Convenience types for common cases: IntArray
type IntArray []int
func (p IntArray) Len() int { return len(p) }
func (p IntArray) Less(i, j int) bool { return p[i] < p[j] }
func (p IntArray) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
type Float64Array []float64
func (p Float64Array) Len() int { return len(p) }
func (p Float64Array) Less(i, j int) bool { return p[i] < p[j] }
func (p Float64Array) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
type StringArray []string
func (p StringArray) Len() int { return len(p) }
func (p StringArray) Less(i, j int) bool { return p[i] < p[j] }
func (p StringArray) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
// Convenience wrappers for common cases
func SortInts(a []int) { Sort(IntArray(a)) }
func SortFloat64s(a []float64) { Sort(Float64Array(a)) }
func SortStrings(a []string) { Sort(StringArray(a)) }
func IntsAreSorted(a []int) bool { return IsSorted(IntArray(a)) }
func Float64sAreSorted(a []float64) bool { return IsSorted(Float64Array(a)) }
func StringsAreSorted(a []string) bool { return IsSorted(StringArray(a)) }

163
eBook/examples/chapter_11/sortmain.go
View File

@@ -1,82 +1,81 @@
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// This package gives an example of how to use a custom package with interfaces
package main
import (
"fmt"
"./sort"
)
// sorting of slice of integers
func ints() {
data := []int{74, 59, 238, -784, 9845, 959, 905, 0, 0, 42, 7586, -5467984, 7586}
a := sort.IntArray(data) //conversion to type IntArray
sort.Sort(a)
if !sort.IsSorted(a) {
panic("fail")
}
fmt.Printf("The sorted array is: %v\n", a)
}
// sorting of slice of strings
func strings() {
data := []string{"monday", "friday", "tuesday", "wednesday", "sunday","thursday", "", "saturday"}
a := sort.StringArray(data)
sort.Sort(a)
if !sort.IsSorted(a) {
panic("fail")
}
fmt.Printf("The sorted array is: %v\n", a)
}
// a type which describes a day of the week
type day struct {
num int
shortName string
longName string
}
type dayArray struct {
data []*day
}
func (p *dayArray) Len() int { return len(p.data) }
func (p *dayArray) Less(i, j int) bool { return p.data[i].num < p.data[j].num }
func (p *dayArray) Swap(i, j int) { p.data[i], p.data[j] = p.data[j], p.data[i] }
// sorting of custom type day
func days() {
Sunday := day{0, "SUN", "Sunday"}
Monday := day{1, "MON", "Monday"}
Tuesday := day{2, "TUE", "Tuesday"}
Wednesday := day{3, "WED", "Wednesday"}
Thursday := day{4, "THU", "Thursday"}
Friday := day{5, "FRI", "Friday"}
Saturday := day{6, "SAT", "Saturday"}
data := []*day{&Tuesday, &Thursday, &Wednesday, &Sunday, &Monday, &Friday, &Saturday}
a := dayArray{data}
sort.Sort(&a)
if !sort.IsSorted(&a) {
panic("fail")
}
for _, d := range data {
fmt.Printf("%s ", d.longName)
}
fmt.Printf("\n")
}
func main() {
ints()
strings()
days()
}
/* Output:
The sorted array is: [-5467984 -784 0 0 42 59 74 238 905 959 7586 7586 9845]
The sorted array is: [ friday monday saturday sunday thursday tuesday wednesday]
Sunday Monday Tuesday Wednesday Thursday Friday Saturday
*/
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// This package gives an example of how to use a custom package with interfaces
package main
import (
"./sort"
"fmt"
)
// sorting of slice of integers
func ints() {
data := []int{74, 59, 238, -784, 9845, 959, 905, 0, 0, 42, 7586, -5467984, 7586}
a := sort.IntArray(data) //conversion to type IntArray
sort.Sort(a)
if !sort.IsSorted(a) {
panic("fail")
}
fmt.Printf("The sorted array is: %v\n", a)
}
// sorting of slice of strings
func strings() {
data := []string{"monday", "friday", "tuesday", "wednesday", "sunday", "thursday", "", "saturday"}
a := sort.StringArray(data)
sort.Sort(a)
if !sort.IsSorted(a) {
panic("fail")
}
fmt.Printf("The sorted array is: %v\n", a)
}
// a type which describes a day of the week
type day struct {
num int
shortName string
longName string
}
type dayArray struct {
data []*day
}
func (p *dayArray) Len() int { return len(p.data) }
func (p *dayArray) Less(i, j int) bool { return p.data[i].num < p.data[j].num }
func (p *dayArray) Swap(i, j int) { p.data[i], p.data[j] = p.data[j], p.data[i] }
// sorting of custom type day
func days() {
Sunday := day{0, "SUN", "Sunday"}
Monday := day{1, "MON", "Monday"}
Tuesday := day{2, "TUE", "Tuesday"}
Wednesday := day{3, "WED", "Wednesday"}
Thursday := day{4, "THU", "Thursday"}
Friday := day{5, "FRI", "Friday"}
Saturday := day{6, "SAT", "Saturday"}
data := []*day{&Tuesday, &Thursday, &Wednesday, &Sunday, &Monday, &Friday, &Saturday}
a := dayArray{data}
sort.Sort(&a)
if !sort.IsSorted(&a) {
panic("fail")
}
for _, d := range data {
fmt.Printf("%s ", d.longName)
}
fmt.Printf("\n")
}
func main() {
ints()
strings()
days()
}
/* Output:
The sorted array is: [-5467984 -784 0 0 42 59 74 238 905 959 7586 7586 9845]
The sorted array is: [ friday monday saturday sunday thursday tuesday wednesday]
Sunday Monday Tuesday Wednesday Thursday Friday Saturday
*/

46
eBook/examples/chapter_11/static.go
View File

@@ -1,23 +1,23 @@
// static.go
package main
import (
"io"
"os"
"bufio"
"bytes"
"fmt"
)
var r io.Reader
func main() {
r = os.Stdin
r = bufio.NewReader(r)
r = new(bytes.Buffer)
f, _ := os.Open("test.txt")
r = bufio.NewReader(f)
var s *bytes.Buffer = new(bytes.Buffer)
r = s
fmt.Println(s)
}
// static.go
package main
import (
"bufio"
"bytes"
"fmt"
"io"
"os"
)
var r io.Reader
func main() {
r = os.Stdin
r = bufio.NewReader(r)
r = new(bytes.Buffer)
f, _ := os.Open("test.txt")
r = bufio.NewReader(f)
var s *bytes.Buffer = new(bytes.Buffer)
r = s
fmt.Println(s)
}

8
eBook/examples/chapter_11/tideland-cgl.googlecode.com/hg/cgl.go
View File

@@ -43,8 +43,8 @@ package cgl
import (
"bytes"
"crypto/rand"
"fmt"
"encoding/hex"
"fmt"
"io"
"log"
"reflect"
@@ -120,7 +120,7 @@ func (uuid UUID) String() string {
// MORE ID FUNCTIONS
//--------------------
// LimitedSepIdentifier builds an identifier out of multiple parts,
// LimitedSepIdentifier builds an identifier out of multiple parts,
// all as lowercase strings and concatenated with the separator
// Non letters and digits are exchanged with dashes and
// reduced to a maximum of one each. If limit is true only
@@ -173,8 +173,8 @@ func Identifier(parts ...interface{}) string {
return SepIdentifier(":", parts...)
}
// TypeAsIdentifierPart transforms the name of the arguments type into
// a part for identifiers. It's splitted at each uppercase char,
// TypeAsIdentifierPart transforms the name of the arguments type into
// a part for identifiers. It's splitted at each uppercase char,
// concatenated with dashes and transferred to lowercase.
func TypeAsIdentifierPart(i interface{}) string {
var buf bytes.Buffer

4
eBook/examples/chapter_11/tideland-cgl.googlecode.com/hg/cglmon.go
View File

@@ -151,7 +151,7 @@ func (sm *SystemMonitor) MeasuringPointsMap(f func(*MeasuringPoint) interface{})
return resp.([]interface{})
}
// MeasuringPointsDo performs the function f for
// MeasuringPointsDo performs the function f for
// all measuring points.
func (sm *SystemMonitor) MeasuringPointsDo(f func(*MeasuringPoint)) {
cmd := &command{cmdMeasuringPointsDo, f, nil}
@@ -450,7 +450,7 @@ type Measuring struct {
endTime int64
}
// EndMEasuring ends a measuring and passes it to the
// EndMEasuring ends a measuring and passes it to the
// measuring server in the background.
func (m *Measuring) EndMeasuring() int64 {
m.endTime = time.Nanoseconds()

124
eBook/examples/chapter_11/type_interfaces.go
View File

@@ -1,62 +1,62 @@
package main
import (
"fmt"
"math"
)
type Square struct {
side float32
}
type Circle struct {
radius float32
}
type Shaper interface {
Area() float32
}
func main() {
var areaIntf Shaper
sq1 := new(Square)
sq1.side = 5
areaIntf = sq1
// Is Square the type of areaIntf ?
if t, ok := areaIntf.(*Square); ok {
fmt.Printf("The type of areaIntf is: %T\n", t)
}
if u, ok := areaIntf.(*Circle); ok {
fmt.Printf("The type of areaIntf is: %T\n", u)
} else {
fmt.Println("areaIntf does not contain a variable of type Circle")
}
// testing with switch:
switch t := areaIntf.(type) {
case *Square:
fmt.Printf("Type Square %T with value %v\n", t, t)
case *Circle:
fmt.Printf("Type Circle %T with value %v\n", t, t)
/*
case bool:
fmt.Printf("Type boolean %t\n", t)
case int:
fmt.Printf("Type int %d\n", t)
case *bool:
fmt.Printf("Type pointer to boolean %t\n", *t)
case *int:
fmt.Printf("Type pointer to int %d\n", *t)
*/
default:
fmt.Printf("Unexpected type %T", t)
}
}
func (sq *Square) Area() float32 {
return sq.side * sq.side
}
func (ci *Circle) Area() float32 {
return ci.radius * ci.radius * math.Pi
}
package main
import (
"fmt"
"math"
)
type Square struct {
side float32
}
type Circle struct {
radius float32
}
type Shaper interface {
Area() float32
}
func main() {
var areaIntf Shaper
sq1 := new(Square)
sq1.side = 5
areaIntf = sq1
// Is Square the type of areaIntf ?
if t, ok := areaIntf.(*Square); ok {
fmt.Printf("The type of areaIntf is: %T\n", t)
}
if u, ok := areaIntf.(*Circle); ok {
fmt.Printf("The type of areaIntf is: %T\n", u)
} else {
fmt.Println("areaIntf does not contain a variable of type Circle")
}
// testing with switch:
switch t := areaIntf.(type) {
case *Square:
fmt.Printf("Type Square %T with value %v\n", t, t)
case *Circle:
fmt.Printf("Type Circle %T with value %v\n", t, t)
/*
case bool:
fmt.Printf("Type boolean %t\n", t)
case int:
fmt.Printf("Type int %d\n", t)
case *bool:
fmt.Printf("Type pointer to boolean %t\n", *t)
case *int:
fmt.Printf("Type pointer to int %d\n", *t)
*/
default:
fmt.Printf("Unexpected type %T", t)
}
}
func (sq *Square) Area() float32 {
return sq.side * sq.side
}
func (ci *Circle) Area() float32 {
return ci.radius * ci.radius * math.Pi
}

71
eBook/examples/chapter_12/cat.go
View File

@@ -1,36 +1,35 @@
package main
import (
"os"
"io"
"fmt"
"bufio"
"flag"
)
func cat(r *bufio.Reader) {
for {
buf, err := r.ReadBytes('\n')
if err == io.EOF {
break
}
fmt.Fprintf(os.Stdout, "%s", buf)
}
return
}
func main() {
flag.Parse()
if flag.NArg() == 0 {
cat(bufio.NewReader(os.Stdin))
}
for i := 0; i < flag.NArg(); i++ {
f, err := os.Open(flag.Arg(i))
if err != nil {
fmt.Fprintf(os.Stderr, "%s:error reading from %s: %s\n", os.Args[0], flag.Arg(i), err.Error())
continue
}
cat(bufio.NewReader(f))
}
}
package main
import (
"bufio"
"flag"
"fmt"
"io"
"os"
)
func cat(r *bufio.Reader) {
for {
buf, err := r.ReadBytes('\n')
if err == io.EOF {
break
}
fmt.Fprintf(os.Stdout, "%s", buf)
}
return
}
func main() {
flag.Parse()
if flag.NArg() == 0 {
cat(bufio.NewReader(os.Stdin))
}
for i := 0; i < flag.NArg(); i++ {
f, err := os.Open(flag.Arg(i))
if err != nil {
fmt.Fprintf(os.Stderr, "%s:error reading from %s: %s\n", os.Args[0], flag.Arg(i), err.Error())
continue
}
cat(bufio.NewReader(f))
}
}

82
eBook/examples/chapter_12/cat2.go
View File

@@ -1,41 +1,41 @@
package main
import (
"flag"
"fmt"
"os"
)
func cat(f *os.File) {
const NBUF = 512
var buf [NBUF]byte
for {
switch nr, err := f.Read(buf[:]); true {
case nr < 0:
fmt.Fprintf(os.Stderr, "cat: error reading: %s\n", err.Error())
os.Exit(1)
case nr == 0: // EOF
return
case nr > 0:
if nw, ew := os.Stdout.Write(buf[0:nr]); nw != nr {
fmt.Fprintf(os.Stderr, "cat: error writing: %s\n", ew.Error())
}
}
}
}
func main() {
flag.Parse() // Scans the arg list and sets up flags
if flag.NArg() == 0 {
cat(os.Stdin)
}
for i := 0; i < flag.NArg(); i++ {
f, err := os.Open(flag.Arg(i))
if f == nil {
fmt.Fprintf(os.Stderr, "cat: can't open %s: error %s\n", flag.Arg(i), err)
os.Exit(1)
}
cat(f)
f.Close()
}
}
package main
import (
"flag"
"fmt"
"os"
)
func cat(f *os.File) {
const NBUF = 512
var buf [NBUF]byte
for {
switch nr, err := f.Read(buf[:]); true {
case nr < 0:
fmt.Fprintf(os.Stderr, "cat: error reading: %s\n", err.Error())
os.Exit(1)
case nr == 0: // EOF
return
case nr > 0:
if nw, ew := os.Stdout.Write(buf[0:nr]); nw != nr {
fmt.Fprintf(os.Stderr, "cat: error writing: %s\n", ew.Error())
}
}
}
}
func main() {
flag.Parse() // Scans the arg list and sets up flags
if flag.NArg() == 0 {
cat(os.Stdin)
}
for i := 0; i < flag.NArg(); i++ {
f, err := os.Open(flag.Arg(i))
if f == nil {
fmt.Fprintf(os.Stderr, "cat: can't open %s: error %s\n", flag.Arg(i), err)
os.Exit(1)
}
cat(f)
f.Close()
}
}

58
eBook/examples/chapter_12/echo.go
View File

@@ -1,29 +1,29 @@
package main
import (
"os"
"flag" // command line option parser
)
var NewLine = flag.Bool("n", false, "print newline") // echo -n flag, of type *bool
const (
Space = " "
Newline = "\n"
)
func main() {
flag.PrintDefaults()
flag.Parse() // Scans the arg list and sets up flags
var s string = ""
for i := 0; i < flag.NArg(); i++ {
if i > 0 {
s += " "
if *NewLine { // -n is parsed, flag becomes true
s += Newline
}
}
s += flag.Arg(i)
}
os.Stdout.WriteString(s)
}
package main
import (
"flag" // command line option parser
"os"
)
var NewLine = flag.Bool("n", false, "print newline") // echo -n flag, of type *bool
const (
Space = " "
Newline = "\n"
)
func main() {
flag.PrintDefaults()
flag.Parse() // Scans the arg list and sets up flags
var s string = ""
for i := 0; i < flag.NArg(); i++ {
if i > 0 {
s += " "
if *NewLine { // -n is parsed, flag becomes true
s += Newline
}
}
s += flag.Arg(i)
}
os.Stdout.WriteString(s)
}

58
eBook/examples/chapter_12/filecopy.go
View File

@@ -1,29 +1,29 @@
// filecopy.go
package main
import (
"fmt"
"io"
"os"
)
func main() {
CopyFile("target.txt", "source.txt")
fmt.Println("Copy done!")
}
func CopyFile(dstName, srcName string) (written int64, err error) {
src, err := os.Open(srcName)
if err != nil {
return
}
defer src.Close()
dst, err := os.OpenFile(dstName, os.O_WRONLY|os.O_CREATE, 0644)
if err != nil {
return
}
defer dst.Close()
return io.Copy(dst, src)
}
// filecopy.go
package main
import (
"fmt"
"io"
"os"
)
func main() {
CopyFile("target.txt", "source.txt")
fmt.Println("Copy done!")
}
func CopyFile(dstName, srcName string) (written int64, err error) {
src, err := os.Open(srcName)
if err != nil {
return
}
defer src.Close()
dst, err := os.OpenFile(dstName, os.O_WRONLY|os.O_CREATE, 0644)
if err != nil {
return
}
defer dst.Close()
return io.Copy(dst, src)
}

68
eBook/examples/chapter_12/fileinput.go
View File

@@ -1,34 +1,34 @@
package main
import (
"bufio"
"fmt"
"io"
"os"
)
func main() {
// var inputFile *os.File
// var inputError, readerError os.Error
// var inputReader *bufio.Reader
// var inputString string
inputFile, inputError := os.Open("input.dat")
if inputError != nil {
fmt.Printf("An error occurred on opening the inputfile\n" +
"Does the file exist?\n" +
"Have you got acces to it?\n")
return // exit the function on error
}
defer inputFile.Close()
inputReader := bufio.NewReader(inputFile)
for {
inputString, readerError := inputReader.ReadString('\n')
if readerError == io.EOF {
return // error or EOF
}
fmt.Printf("The input was: %s", inputString)
}
}
package main
import (
"bufio"
"fmt"
"io"
"os"
)
func main() {
// var inputFile *os.File
// var inputError, readerError os.Error
// var inputReader *bufio.Reader
// var inputString string
inputFile, inputError := os.Open("input.dat")
if inputError != nil {
fmt.Printf("An error occurred on opening the inputfile\n" +
"Does the file exist?\n" +
"Have you got acces to it?\n")
return // exit the function on error
}
defer inputFile.Close()
inputReader := bufio.NewReader(inputFile)
for {
inputString, readerError := inputReader.ReadString('\n')
if readerError == io.EOF {
return // error or EOF
}
fmt.Printf("The input was: %s", inputString)
}
}

56
eBook/examples/chapter_12/fileoutput.go
View File

@@ -1,28 +1,28 @@
package main
import (
"os"
"bufio"
"fmt"
)
func main () {
// var outputWriter *bufio.Writer
// var outputFile *os.File
// var outputError os.Error
// var outputString string
outputFile, outputError := os.OpenFile("output.dat", os.O_WRONLY|os.O_CREATE, 0666)
if outputError != nil {
fmt.Printf("An error occurred with file opening or creation\n")
return
}
defer outputFile.Close()
outputWriter := bufio.NewWriter(outputFile)
outputString := "hello world!\n"
for i:=0; i<10; i++ {
outputWriter.WriteString(outputString)
}
outputWriter.Flush()
}
package main
import (
"bufio"
"fmt"
"os"
)
func main() {
// var outputWriter *bufio.Writer
// var outputFile *os.File
// var outputError os.Error
// var outputString string
outputFile, outputError := os.OpenFile("output.dat", os.O_WRONLY|os.O_CREATE, 0666)
if outputError != nil {
fmt.Printf("An error occurred with file opening or creation\n")
return
}
defer outputFile.Close()
outputWriter := bufio.NewWriter(outputFile)
outputString := "hello world!\n"
for i := 0; i < 10; i++ {
outputWriter.WriteString(outputString)
}
outputWriter.Flush()
}

20
eBook/examples/chapter_12/filewrite.go
View File

@@ -1,10 +1,10 @@
package main
import "os"
func main() {
os.Stdout.WriteString("hello, world\n")
f, _ := os.OpenFile("test", os.O_CREATE|os.O_WRONLY, 0)
defer f.Close()
f.WriteString("hello, world in a file\n")
}
package main
import "os"
func main() {
os.Stdout.WriteString("hello, world\n")
f, _ := os.OpenFile("test", os.O_CREATE|os.O_WRONLY, 0)
defer f.Close()
f.WriteString("hello, world in a file\n")
}

83
eBook/examples/chapter_12/gob1.go
View File

@@ -1,41 +1,42 @@
// gob1.go
package main
import (
"bytes"
"fmt"
"encoding/gob"
"log"
)
type P struct {
X, Y, Z int
Name string
}
type Q struct {
X, Y *int32
Name string
}
func main() {
// Initialize the encoder and decoder. Normally enc and dec would be
// bound to network connections and the encoder and decoder would
// run in different processes.
var network bytes.Buffer // Stand-in for a network connection
enc := gob.NewEncoder(&network) // Will write to network.
dec := gob.NewDecoder(&network) // Will read from network.
// Encode (send) the value.
err := enc.Encode(P{3, 4, 5, "Pythagoras"})
if err != nil {
log.Fatal("encode error:", err)
}
// Decode (receive) the value.
var q Q
err = dec.Decode(&q)
if err != nil {
log.Fatal("decode error:", err)
}
fmt.Printf("%q: {%d,%d}\n", q.Name, *q.X, *q.Y)
}
// Output: "Pythagoras": {3,4}
// gob1.go
package main
import (
"bytes"
"encoding/gob"
"fmt"
"log"
)
type P struct {
X, Y, Z int
Name string
}
type Q struct {
X, Y *int32
Name string
}
func main() {
// Initialize the encoder and decoder. Normally enc and dec would be
// bound to network connections and the encoder and decoder would
// run in different processes.
var network bytes.Buffer // Stand-in for a network connection
enc := gob.NewEncoder(&network) // Will write to network.
dec := gob.NewDecoder(&network) // Will read from network.
// Encode (send) the value.
err := enc.Encode(P{3, 4, 5, "Pythagoras"})
if err != nil {
log.Fatal("encode error:", err)
}
// Decode (receive) the value.
var q Q
err = dec.Decode(&q)
if err != nil {
log.Fatal("decode error:", err)
}
fmt.Printf("%q: {%d,%d}\n", q.Name, *q.X, *q.Y)
}
// Output: "Pythagoras": {3,4}

77
eBook/examples/chapter_12/gob2.go
View File

@@ -1,39 +1,38 @@
// gob2.go
package main
import (
"encoding/gob"
"log"
"os"
)
type Address struct {
Type string
City string
Country string
}
type VCard struct {
FirstName string
LastName string
Addresses []*Address
Remark string
}
var content string
func main() {
pa := &Address{"private", "Aartselaar","Belgium"}
wa := &Address{"work", "Boom", "Belgium"}
vc := VCard{"Jan", "Kersschot", []*Address{pa,wa}, "none"}
// fmt.Printf("%v: \n", vc) // {Jan Kersschot [0x126d2b80 0x126d2be0] none}:
// using an encoder:
file, _ := os.OpenFile("vcard.gob", os.O_CREATE|os.O_WRONLY, 0666)
defer file.Close()
enc := gob.NewEncoder(file)
err := enc.Encode(vc)
if err != nil {
log.Println("Error in encoding gob")
}
}
// gob2.go
package main
import (
"encoding/gob"
"log"
"os"
)
type Address struct {
Type string
City string
Country string
}
type VCard struct {
FirstName string
LastName string
Addresses []*Address
Remark string
}
var content string
func main() {
pa := &Address{"private", "Aartselaar", "Belgium"}
wa := &Address{"work", "Boom", "Belgium"}
vc := VCard{"Jan", "Kersschot", []*Address{pa, wa}, "none"}
// fmt.Printf("%v: \n", vc) // {Jan Kersschot [0x126d2b80 0x126d2be0] none}:
// using an encoder:
file, _ := os.OpenFile("vcard.gob", os.O_CREATE|os.O_WRONLY, 0666)
defer file.Close()
enc := gob.NewEncoder(file)
err := enc.Encode(vc)
if err != nil {
log.Println("Error in encoding gob")
}
}

70
eBook/examples/chapter_12/gzipped.go
View File

@@ -1,35 +1,35 @@
// gzipped.go
package main
import (
"fmt"
"bufio"
"os"
"compress/gzip"
)
func main() {
fName := "MyFile.gz"
var r *bufio.Reader
fi, err := os.Open(fName)
if err != nil {
fmt.Fprintf(os.Stderr, "%v, Can't open %s: error: %s\n", os.Args[0], fName,
err)
os.Exit(1)
}
fz, err := gzip.NewReader(fi)
if err != nil {
r = bufio.NewReader(fi)
} else {
r = bufio.NewReader(fz)
}
for {
line, err := r.ReadString('\n')
if err != nil {
fmt.Println("Done reading file")
os.Exit(0)
}
fmt.Println(line)
}
}
// gzipped.go
package main
import (
"bufio"
"compress/gzip"
"fmt"
"os"
)
func main() {
fName := "MyFile.gz"
var r *bufio.Reader
fi, err := os.Open(fName)
if err != nil {
fmt.Fprintf(os.Stderr, "%v, Can't open %s: error: %s\n", os.Args[0], fName,
err)
os.Exit(1)
}
fz, err := gzip.NewReader(fi)
if err != nil {
r = bufio.NewReader(fi)
} else {
r = bufio.NewReader(fz)
}
for {
line, err := r.ReadString('\n')
if err != nil {
fmt.Println("Done reading file")
os.Exit(0)
}
fmt.Println(line)
}
}

63
eBook/examples/chapter_12/hash_sha1.go
View File

@@ -1,31 +1,32 @@
// hash_sha1.go
package main
import (
"fmt"
"crypto/sha1"
"io"
"log"
)
func main() {
hasher := sha1.New()
io.WriteString(hasher, "test")
b := []byte{}
fmt.Printf("Result: %x\n", hasher.Sum(b))
fmt.Printf("Result: %d\n", hasher.Sum(b))
//
hasher.Reset()
data := []byte("We shall overcome!")
n, err := hasher.Write(data)
if n!=len(data) || err!=nil {
log.Printf("Hash write error: %v / %v", n, err)
}
checksum := hasher.Sum(b)
fmt.Printf("Result: %x\n", checksum)
}
/* Output:
Result: a94a8fe5ccb19ba61c4c0873d391e987982fbbd3
Result: [169 74 143 229 204 177 155 166 28 76 8 115 211 145 233 135 152 47 187 211]
Result: e2222bfc59850bbb00a722e764a555603bb59b2a
*/
// hash_sha1.go
package main
import (
"crypto/sha1"
"fmt"
"io"
"log"
)
func main() {
hasher := sha1.New()
io.WriteString(hasher, "test")
b := []byte{}
fmt.Printf("Result: %x\n", hasher.Sum(b))
fmt.Printf("Result: %d\n", hasher.Sum(b))
//
hasher.Reset()
data := []byte("We shall overcome!")
n, err := hasher.Write(data)
if n != len(data) || err != nil {
log.Printf("Hash write error: %v / %v", n, err)
}
checksum := hasher.Sum(b)
fmt.Printf("Result: %x\n", checksum)
}
/* Output:
Result: a94a8fe5ccb19ba61c4c0873d391e987982fbbd3
Result: [169 74 143 229 204 177 155 166 28 76 8 115 211 145 233 135 152 47 187 211]
Result: e2222bfc59850bbb00a722e764a555603bb59b2a
*/

36
eBook/examples/chapter_12/io_interfaces.go
View File

@@ -1,18 +1,18 @@
// interfaces being used in the GO-package fmt
package main
import (
"bufio"
"fmt"
"os"
)
func main() {
// unbuffered
fmt.Fprintf(os.Stdout, "%s\n", "hello world! - unbuffered")
// buffered: os.Stdout implements io.Writer
buf := bufio.NewWriter(os.Stdout)
// and now so does buf.
fmt.Fprintf(buf, "%s\n", "hello world! - buffered")
buf.Flush()
}
// interfaces being used in the GO-package fmt
package main
import (
"bufio"
"fmt"
"os"
)
func main() {
// unbuffered
fmt.Fprintf(os.Stdout, "%s\n", "hello world! - unbuffered")
// buffered: os.Stdout implements io.Writer
buf := bufio.NewWriter(os.Stdout)
// and now so does buf.
fmt.Fprintf(buf, "%s\n", "hello world! - buffered")
buf.Flush()
}

80
eBook/examples/chapter_12/json.go
View File

@@ -1,40 +1,40 @@
// json.go
package main
import (
"fmt"
"encoding/json"
"log"
"os"
)
type Address struct {
Type string
City string
Country string
}
type VCard struct {
FirstName string
LastName string
Addresses []*Address
Remark string
}
func main() {
pa := &Address{"private", "Aartselaar","Belgium"}
wa := &Address{"work", "Boom", "Belgium"}
vc := VCard{"Jan", "Kersschot", []*Address{pa,wa}, "none"}
// fmt.Printf("%v: \n", vc) // {Jan Kersschot [0x126d2b80 0x126d2be0] none}:
// JSON format:
js, _ := json.Marshal(vc)
fmt.Printf("JSON format: %s", js)
// using an encoder:
file, _ := os.OpenFile("vcard.json", os.O_CREATE|os.O_WRONLY, 0)
defer file.Close()
enc := json.NewEncoder(file)
err := enc.Encode(vc)
if err != nil {
log.Println("Error in encoding json")
}
}
// json.go
package main
import (
"encoding/json"
"fmt"
"log"
"os"
)
type Address struct {
Type string
City string
Country string
}
type VCard struct {
FirstName string
LastName string
Addresses []*Address
Remark string
}
func main() {
pa := &Address{"private", "Aartselaar", "Belgium"}
wa := &Address{"work", "Boom", "Belgium"}
vc := VCard{"Jan", "Kersschot", []*Address{pa, wa}, "none"}
// fmt.Printf("%v: \n", vc) // {Jan Kersschot [0x126d2b80 0x126d2be0] none}:
// JSON format:
js, _ := json.Marshal(vc)
fmt.Printf("JSON format: %s", js)
// using an encoder:
file, _ := os.OpenFile("vcard.json", os.O_CREATE|os.O_WRONLY, 0)
defer file.Close()
enc := json.NewEncoder(file)
err := enc.Encode(vc)
if err != nil {
log.Println("Error in encoding json")
}
}

109
eBook/examples/chapter_12/json_xml_case.go
View File

@@ -1,54 +1,55 @@
// json_xml_case.go
package main
import (
"encoding/json"
"encoding/xml"
"fmt"
"log"
"strings"
)
type thing struct {
Field1 int
Field2 string
}
func main() {
x := `<x><field1>423</field1><field2>hello from xml</field2></x>`
j := `{"field1": 423, "field2": "hello from json"}`
tx := thing{}
if err := xml.Unmarshal(strings.NewReader(x), &tx); err != nil {
log.Fatalf("Error unmarshaling XML: %v", err)
}
tj := thing{}
if err := json.Unmarshal([]byte(j), &tj); err != nil {
log.Fatalf("Error unmarshaling JSON: %v", err)
}
fmt.Printf("From JSON: %#v\n", tj)
fmt.Printf("From XML: %#v\n", tx)
}
/* Output with
type thing struct {
Field1 int
Field2 string
}:
From XML: main.thing{Field1:0, Field2:""} // All matching is case sensitive!
From JSON: main.thing{Field1:423, Field2:"hello from json"}
Output with
type thing struct {
field1 int
field2 string
}:
2012/02/22 10:51:11 Error unmarshaling JSON: json: cannot unmarshal object
field1" into unexported field field1 of type main.thing
JSON uses reflection to unmarshal!
*/
// json_xml_case.go
package main
import (
"encoding/json"
"encoding/xml"
"fmt"
"log"
"strings"
)
type thing struct {
Field1 int
Field2 string
}
func main() {
x := `<x><field1>423</field1><field2>hello from xml</field2></x>`
j := `{"field1": 423, "field2": "hello from json"}`
tx := thing{}
if err := xml.Unmarshal(strings.NewReader(x), &tx); err != nil {
log.Fatalf("Error unmarshaling XML: %v", err)
}
tj := thing{}
if err := json.Unmarshal([]byte(j), &tj); err != nil {
log.Fatalf("Error unmarshaling JSON: %v", err)
}
fmt.Printf("From JSON: %#v\n", tj)
fmt.Printf("From XML: %#v\n", tx)
}
/* Output with
type thing struct {
Field1 int
Field2 string
}:
From XML: main.thing{Field1:0, Field2:""} // All matching is case sensitive!
From JSON: main.thing{Field1:423, Field2:"hello from json"}
Output with
type thing struct {
field1 int
field2 string
}:
2012/02/22 10:51:11 Error unmarshaling JSON: json: cannot unmarshal object
field1" into unexported field field1 of type main.thing
JSON uses reflection to unmarshal!
*/

32
eBook/examples/chapter_12/os_args.go
View File

@@ -1,16 +1,16 @@
// os_args.go
package main
import (
"fmt"
"os"
"strings"
)
func main() {
who := "Alice "
if len(os.Args) > 1 {
who += strings.Join(os.Args[1:], " ")
}
fmt.Println("Good Morning", who)
}
// os_args.go
package main
import (
"fmt"
"os"
"strings"
)
func main() {
who := "Alice "
if len(os.Args) > 1 {
who += strings.Join(os.Args[1:], " ")
}
fmt.Println("Good Morning", who)
}

77
eBook/examples/chapter_12/read_file2.go
View File

@@ -1,38 +1,39 @@
// read_csvfile.go
package main
import (
"fmt"
"os"
// "io/ioutil"
// "strings"
)
func main() {
file, err := os.Open("products2.txt")
if err != nil {
panic(err)
}
defer file.Close()
var col1, col2, col3 []string
for {
var v1, v2, v3 string
_, err := fmt.Fscanln(file, &v1, &v2, &v3)
if err != nil {
break
}
col1 = append(col1, v1)
col2 = append(col2, v2)
col3 = append(col3, v3)
}
fmt.Println(col1)
fmt.Println(col2)
fmt.Println(col3)
}
/* Output:
[ABC FUNC GO]
[40 56 45]
[150 280 356]
*/
// read_csvfile.go
package main
import (
"fmt"
"os"
// "io/ioutil"
// "strings"
)
func main() {
file, err := os.Open("products2.txt")
if err != nil {
panic(err)
}
defer file.Close()
var col1, col2, col3 []string
for {
var v1, v2, v3 string
_, err := fmt.Fscanln(file, &v1, &v2, &v3)
if err != nil {
break
}
col1 = append(col1, v1)
col2 = append(col2, v2)
col3 = append(col3, v3)
}
fmt.Println(col1)
fmt.Println(col2)
fmt.Println(col3)
}
/* Output:
[ABC FUNC GO]
[40 56 45]
[150 280 356]
*/

58
eBook/examples/chapter_12/read_files.go
View File

@@ -1,30 +1,28 @@
// read_files.go
package main
import (
"bufio"
"flag"
"fmt"
"io"
"os"
)
func main() {
fmt.Printf("Reading files...\n")
flag.Parse()
for i := 0; i < flag.NArg(); i++ {
fmt.Printf("[File: %v]\n", flag.Arg(i))
fin, err := os.Open(flag.Arg(i))
if err != nil {
fmt.Printf("The file %v does not exist!\n", flag.Arg(i))
break
}
r := bufio.NewReader(fin)
for line, _, err := r.ReadLine();
err != io.EOF;
line, _, err = r.ReadLine() {
fmt.Printf("Lines: %v (error %v)\n", string(line), err)
}
}
}
// read_files.go
package main
import (
"bufio"
"flag"
"fmt"
"io"
"os"
)
func main() {
fmt.Printf("Reading files...\n")
flag.Parse()
for i := 0; i < flag.NArg(); i++ {
fmt.Printf("[File: %v]\n", flag.Arg(i))
fin, err := os.Open(flag.Arg(i))
if err != nil {
fmt.Printf("The file %v does not exist!\n", flag.Arg(i))
break
}
r := bufio.NewReader(fin)
for line, _, err := r.ReadLine(); err != io.EOF; line, _, err = r.ReadLine() {
fmt.Printf("Lines: %v (error %v)\n", string(line), err)
}
}
}

42
eBook/examples/chapter_12/read_write_file1.go
View File

@@ -1,21 +1,21 @@
// read_write_file.go
package main
import (
"fmt"
"io/ioutil"
)
func main() {
inputFile := "products.txt"
outputFile := "products_copy.txt"
buf, err := ioutil.ReadFile(inputFile)
if err != nil {
panic(err.Error())
}
fmt.Printf("%s\n", string(buf))
err = ioutil.WriteFile(outputFile, buf, 0644) // oct, not hex
if err != nil {
panic(err.Error())
}
}
// read_write_file.go
package main
import (
"fmt"
"io/ioutil"
)
func main() {
inputFile := "products.txt"
outputFile := "products_copy.txt"
buf, err := ioutil.ReadFile(inputFile)
if err != nil {
panic(err.Error())
}
fmt.Printf("%s\n", string(buf))
err = ioutil.WriteFile(outputFile, buf, 0644) // oct, not hex
if err != nil {
panic(err.Error())
}
}

48
eBook/examples/chapter_12/readinput1.go
View File

@@ -1,24 +1,24 @@
// read input from the console:
package main
import (
"fmt"
)
var (
firstName, lastName, s string
i int
f float32
input = "56.12 / 5212 / Go"
format = "%f / %d / %s"
)
func main() {
fmt.Println("Please enter your full name: ")
fmt.Scanln(&firstName, &lastName)
// fmt.Scanf("%s %s", &firstName, &lastName)
fmt.Printf("Hi %s %s!\n", firstName, lastName) // Hi Chris Naegels
fmt.Sscanf(input, format, &f, &i, &s)
fmt.Println("From the string we read: ", f, i, s) // From the string we read: 56.12 5212 Go
}
// read input from the console:
package main
import (
"fmt"
)
var (
firstName, lastName, s string
i int
f float32
input = "56.12 / 5212 / Go"
format = "%f / %d / %s"
)
func main() {
fmt.Println("Please enter your full name: ")
fmt.Scanln(&firstName, &lastName)
// fmt.Scanf("%s %s", &firstName, &lastName)
fmt.Printf("Hi %s %s!\n", firstName, lastName) // Hi Chris Naegels
fmt.Sscanf(input, format, &f, &i, &s)
fmt.Println("From the string we read: ", f, i, s) // From the string we read: 56.12 5212 Go
}

44
eBook/examples/chapter_12/readinput2.go
View File

@@ -1,22 +1,22 @@
// read input from the console:
package main
import (
"fmt"
"bufio"
"os"
)
var inputReader *bufio.Reader
var input string
var err error
func main() {
inputReader = bufio.NewReader(os.Stdin) // reader for input
fmt.Println("Please enter some input: ")
input, err = inputReader.ReadString('\n')
if err == nil {
fmt.Printf("The input was: %s\n", input)
}
}
// read input from the console:
package main
import (
"bufio"
"fmt"
"os"
)
var inputReader *bufio.Reader
var input string
var err error
func main() {
inputReader = bufio.NewReader(os.Stdin) // reader for input
fmt.Println("Please enter some input: ")
input, err = inputReader.ReadString('\n')
if err == nil {
fmt.Printf("The input was: %s\n", input)
}
}

92
eBook/examples/chapter_12/switch_input.go
View File

@@ -1,41 +1,51 @@
package main
import (
"fmt"
"os"
"bufio"
)
func main() {
inputReader := bufio.NewReader(os.Stdin)
fmt.Println("Please enter your name:")
input, err := inputReader.ReadString('\n')
if err != nil {
fmt.Println("There were errors reading, exiting program.")
return
}
fmt.Printf("Your name is %s", input)
// For Unix: test with delimiter "\n", for Windows: test with "\r\n"
switch input {
case "Philip\r\n": fmt.Println("Welcome Philip!")
case "Chris\r\n": fmt.Println("Welcome Chris!")
case "Ivo\r\n": fmt.Println("Welcome Ivo!")
default: fmt.Printf("You are not welcome here! Goodbye!")
}
// version 2:
switch input {
case "Philip\r\n": fallthrough
case "Ivo\r\n": fallthrough
case "Chris\r\n": fmt.Printf("Welcome %s\n", input)
default: fmt.Printf("You are not welcome here! Goodbye!\n")
}
// version 3:
switch input {
case "Philip\r\n", "Ivo\r\n": fmt.Printf("Welcome %s\n", input)
default: fmt.Printf("You are not welcome here! Goodbye!\n")
}
}
package main
import (
"bufio"
"fmt"
"os"
)
func main() {
inputReader := bufio.NewReader(os.Stdin)
fmt.Println("Please enter your name:")
input, err := inputReader.ReadString('\n')
if err != nil {
fmt.Println("There were errors reading, exiting program.")
return
}
fmt.Printf("Your name is %s", input)
// For Unix: test with delimiter "\n", for Windows: test with "\r\n"
switch input {
case "Philip\r\n":
fmt.Println("Welcome Philip!")
case "Chris\r\n":
fmt.Println("Welcome Chris!")
case "Ivo\r\n":
fmt.Println("Welcome Ivo!")
default:
fmt.Printf("You are not welcome here! Goodbye!")
}
// version 2:
switch input {
case "Philip\r\n":
fallthrough
case "Ivo\r\n":
fallthrough
case "Chris\r\n":
fmt.Printf("Welcome %s\n", input)
default:
fmt.Printf("You are not welcome here! Goodbye!\n")
}
// version 3:
switch input {
case "Philip\r\n", "Ivo\r\n":
fmt.Printf("Welcome %s\n", input)
default:
fmt.Printf("You are not welcome here! Goodbye!\n")
}
}

99
eBook/examples/chapter_12/xml.go
View File

@@ -1,49 +1,50 @@
// xml.go
package main
import (
"fmt"
"strings"
"encoding/xml"
)
var t, token xml.Token
var err error
func main() {
input := "<Person><FirstName>Laura</FirstName><LastName>Lynn</LastName></Person>"
inputReader := strings.NewReader(input)
p := xml.NewDecoder(inputReader)
for t, err = p.Token(); err == nil; t, err = p.Token() {
switch token := t.(type) {
case xml.StartElement:
name := token.Name.Local
fmt.Printf("Token name: %s\n", name)
for _, attr := range token.Attr {
attrName := attr.Name.Local
attrValue := attr.Value
fmt.Printf("An attribute is: %s %s\n", attrName, attrValue)
// ...
}
case xml.EndElement:
fmt.Println("End of token")
case xml.CharData:
content := string([]byte(token))
fmt.Printf("This is the content: %v\n", content )
// ...
default:
// ...
}
}
}
/* Output:
Token name: Person
Token name: FirstName
This is the content: Laura
End of token
Token name: LastName
This is the content: Lynn
End of token
End of token
*/
// xml.go
package main
import (
"encoding/xml"
"fmt"
"strings"
)
var t, token xml.Token
var err error
func main() {
input := "<Person><FirstName>Laura</FirstName><LastName>Lynn</LastName></Person>"
inputReader := strings.NewReader(input)
p := xml.NewDecoder(inputReader)
for t, err = p.Token(); err == nil; t, err = p.Token() {
switch token := t.(type) {
case xml.StartElement:
name := token.Name.Local
fmt.Printf("Token name: %s\n", name)
for _, attr := range token.Attr {
attrName := attr.Name.Local
attrValue := attr.Value
fmt.Printf("An attribute is: %s %s\n", attrName, attrValue)
// ...
}
case xml.EndElement:
fmt.Println("End of token")
case xml.CharData:
content := string([]byte(token))
fmt.Printf("This is the content: %v\n", content)
// ...
default:
// ...
}
}
}
/* Output:
Token name: Person
Token name: FirstName
This is the content: Laura
End of token
Token name: LastName
This is the content: Lynn
End of token
End of token
*/

29
eBook/examples/chapter_13/errors.go
View File

@@ -1,14 +1,15 @@
// errors.go
package main
import (
"errors"
"fmt"
)
var errNotFound error = errors.New("Not found error")
func main() {
fmt.Printf("error: %v", errNotFound)
}
// error: Not found error
// errors.go
package main
import (
"errors"
"fmt"
)
var errNotFound error = errors.New("Not found error")
func main() {
fmt.Printf("error: %v", errNotFound)
}
// error: Not found error

20
eBook/examples/chapter_13/even/even/even.go
View File

@@ -1,10 +1,10 @@
// even.go
package even
func Even(i int) bool { // Exported function
return i%2 == 0
}
func Odd(i int) bool { // Exported function
return i%2 != 0
}
// even.go
package even
func Even(i int) bool { // Exported function
return i%2 == 0
}
func Odd(i int) bool { // Exported function
return i%2 != 0
}

54
eBook/examples/chapter_13/even/even/oddeven_test.go
View File

@@ -1,27 +1,27 @@
// oddeven_test.go
package even
import "testing"
func TestEven(t *testing.T) {
if !Even(10) {
t.Log(" 10 must be even!")
t.Fail()
}
if Even(7) {
t.Log(" 7 is not even!")
t.Fail()
}
}
func TestOdd(t *testing.T) {
if !Odd(11) {
t.Log(" 11 must be odd!")
t.Fail()
}
if Odd(10) {
t.Log(" 10 is not odd!")
t.Fail()
}
}
// oddeven_test.go
package even
import "testing"
func TestEven(t *testing.T) {
if !Even(10) {
t.Log(" 10 must be even!")
t.Fail()
}
if Even(7) {
t.Log(" 7 is not even!")
t.Fail()
}
}
func TestOdd(t *testing.T) {
if !Odd(11) {
t.Log(" 11 must be odd!")
t.Fail()
}
if Odd(10) {
t.Log(" 10 is not odd!")
t.Fail()
}
}

26
eBook/examples/chapter_13/even/even_main/even_main.go
View File

@@ -1,13 +1,13 @@
// test_oddeven.go
package main
import (
"fmt"
"even/even"
)
func main() {
for i:=0; i<=100; i++ {
fmt.Printf("Is the integer %d even? %v\n", i, even.Even(i))
}
}
// test_oddeven.go
package main
import (
"even/even"
"fmt"
)
func main() {
for i := 0; i <= 100; i++ {
fmt.Printf("Is the integer %d even? %v\n", i, even.Even(i))
}
}

122
eBook/examples/chapter_13/exec.go
View File

@@ -1,61 +1,61 @@
// exec.go
package main
import (
"fmt"
"os/exec"
"os"
)
func main() {
// 1) os.StartProcess //
/*********************/
/* Linux: */
env := os.Environ()
procAttr := &os.ProcAttr{
Env: env,
Files: []*os.File{
os.Stdin,
os.Stdout,
os.Stderr,
},
}
// 1st example: list files
pid, err := os.StartProcess("/bin/ls", []string{"ls", "-l"}, procAttr)
if err != nil {
fmt.Printf("Error %v starting process!", err) //
os.Exit(1)
}
fmt.Printf("The process id is %v", pid)
// 2nd example: show all processes
pid, err = os.StartProcess("/bin/ps", []string{"-e", "-opid,ppid,comm"}, procAttr)
if err != nil {
fmt.Printf("Error %v starting process!", err) //
os.Exit(1)
}
fmt.Printf("The process id is %v", pid)
/* Output 1st:
The process id is &{2054 0}total 2056
-rwxr-xr-x 1 ivo ivo 1157555 2011-07-04 16:48 Mieken_exec
-rw-r--r-- 1 ivo ivo 2124 2011-07-04 16:48 Mieken_exec.go
-rw-r--r-- 1 ivo ivo 18528 2011-07-04 16:48 Mieken_exec_go_.6
-rwxr-xr-x 1 ivo ivo 913920 2011-06-03 16:13 panic.exe
-rw-r--r-- 1 ivo ivo 180 2011-04-11 20:39 panic.go
*/
// 2) exec.Run //
/***************/
// Linux: OK, but not for ls ?
// cmd := exec.Command("ls", "-l") // no error, but doesn't show anything ?
// cmd := exec.Command("ls") // no error, but doesn't show anything ?
cmd := exec.Command("gedit") // this opens a gedit-window
err = cmd.Run()
if err != nil {
fmt.Printf("Error %v executing command!", err)
os.Exit(1)
}
fmt.Printf("The command is %v", cmd)
// The command is &{/bin/ls [ls -l] [] <nil> <nil> <nil> 0xf840000210 <nil> true [0xf84000ea50 0xf84000e9f0 0xf84000e9c0] [0xf84000ea50 0xf84000e9f0 0xf84000e9c0] [] [] 0xf8400128c0}
}
// in Windows: uitvoering: Error fork/exec /bin/ls: The system cannot find the path specified. starting process!
// exec.go
package main
import (
"fmt"
"os"
"os/exec"
)
func main() {
// 1) os.StartProcess //
/*********************/
/* Linux: */
env := os.Environ()
procAttr := &os.ProcAttr{
Env: env,
Files: []*os.File{
os.Stdin,
os.Stdout,
os.Stderr,
},
}
// 1st example: list files
pid, err := os.StartProcess("/bin/ls", []string{"ls", "-l"}, procAttr)
if err != nil {
fmt.Printf("Error %v starting process!", err) //
os.Exit(1)
}
fmt.Printf("The process id is %v", pid)
// 2nd example: show all processes
pid, err = os.StartProcess("/bin/ps", []string{"-e", "-opid,ppid,comm"}, procAttr)
if err != nil {
fmt.Printf("Error %v starting process!", err) //
os.Exit(1)
}
fmt.Printf("The process id is %v", pid)
/* Output 1st:
The process id is &{2054 0}total 2056
-rwxr-xr-x 1 ivo ivo 1157555 2011-07-04 16:48 Mieken_exec
-rw-r--r-- 1 ivo ivo 2124 2011-07-04 16:48 Mieken_exec.go
-rw-r--r-- 1 ivo ivo 18528 2011-07-04 16:48 Mieken_exec_go_.6
-rwxr-xr-x 1 ivo ivo 913920 2011-06-03 16:13 panic.exe
-rw-r--r-- 1 ivo ivo 180 2011-04-11 20:39 panic.go
*/
// 2) exec.Run //
/***************/
// Linux: OK, but not for ls ?
// cmd := exec.Command("ls", "-l") // no error, but doesn't show anything ?
// cmd := exec.Command("ls") // no error, but doesn't show anything ?
cmd := exec.Command("gedit") // this opens a gedit-window
err = cmd.Run()
if err != nil {
fmt.Printf("Error %v executing command!", err)
os.Exit(1)
}
fmt.Printf("The command is %v", cmd)
// The command is &{/bin/ls [ls -l] [] <nil> <nil> <nil> 0xf840000210 <nil> true [0xf84000ea50 0xf84000e9f0 0xf84000e9c0] [0xf84000ea50 0xf84000e9f0 0xf84000e9c0] [] [] 0xf8400128c0}
}
// in Windows: uitvoering: Error fork/exec /bin/ls: The system cannot find the path specified. starting process!

18
eBook/examples/chapter_13/panic.go
View File

@@ -1,9 +1,9 @@
package main
import "fmt"
func main() {
fmt.Println("Starting the program")
panic("A severe error occurred: stopping the program!")
fmt.Println("Ending the program")
}
package main
import "fmt"
func main() {
fmt.Println("Starting the program")
panic("A severe error occurred: stopping the program!")
fmt.Println("Ending the program")
}

79
eBook/examples/chapter_13/panic_package.go
View File

@@ -1,39 +1,40 @@
// panic_package.go
package main
import (
"fmt"
"./parse/parse"
)
func main() {
var examples = []string{
"1 2 3 4 5",
"100 50 25 12.5 6.25",
"2 + 2 = 4",
"1st class",
"",
}
for _, ex := range examples {
fmt.Printf("Parsing %q:\n ", ex)
nums, err := parse.Parse(ex)
if err != nil {
fmt.Println(err) // here String() method from ParseError is used
continue
}
fmt.Println(nums)
}
}
/* Output:
Parsing "1 2 3 4 5":
[1 2 3 4 5]
Parsing "100 50 25 12.5 6.25":
pkg parse: error parsing "12.5" as int
Parsing "2 + 2 = 4":
pkg parse: error parsing "+" as int
Parsing "1st class":
pkg parse: error parsing "1st" as int
Parsing "":
pkg: no words to parse
*/
// panic_package.go
package main
import (
"./parse/parse"
"fmt"
)
func main() {
var examples = []string{
"1 2 3 4 5",
"100 50 25 12.5 6.25",
"2 + 2 = 4",
"1st class",
"",
}
for _, ex := range examples {
fmt.Printf("Parsing %q:\n ", ex)
nums, err := parse.Parse(ex)
if err != nil {
fmt.Println(err) // here String() method from ParseError is used
continue
}
fmt.Println(nums)
}
}
/* Output:
Parsing "1 2 3 4 5":
[1 2 3 4 5]
Parsing "100 50 25 12.5 6.25":
pkg parse: error parsing "12.5" as int
Parsing "2 + 2 = 4":
pkg parse: error parsing "+" as int
Parsing "1st class":
pkg parse: error parsing "1st" as int
Parsing "":
pkg: no words to parse
*/

64
eBook/examples/chapter_13/panic_recover.go
View File

@@ -1,32 +1,32 @@
// panic_recover.go
package main
import (
"fmt"
)
func badCall() {
panic("bad end")
}
func test() {
defer func() {
if e := recover(); e != nil {
fmt.Printf("Panicing %s\r\n", e)
}
}()
badCall()
fmt.Printf("After bad call\r\n") // <-- wordt niet bereikt
}
func main() {
fmt.Printf("Calling test\r\n")
test()
fmt.Printf("Test completed\r\n")
}
/* Output:
Calling test
Panicing bad end
Test completed
*/
// panic_recover.go
package main
import (
"fmt"
)
func badCall() {
panic("bad end")
}
func test() {
defer func() {
if e := recover(); e != nil {
fmt.Printf("Panicing %s\r\n", e)
}
}()
badCall()
fmt.Printf("After bad call\r\n") // <-- wordt niet bereikt
}
func main() {
fmt.Printf("Calling test\r\n")
test()
fmt.Printf("Test completed\r\n")
}
/* Output:
Calling test
Panicing bad end
Test completed
*/

102
eBook/examples/chapter_13/parse/parse.go
View File

@@ -1,51 +1,51 @@
// parse.go
package parse
import (
"fmt"
"strings"
"strconv"
)
// A ParseError indicates an error in converting a word into an integer.
type ParseError struct {
Index int // The index into the space-separated list of words.
Word string // The word that generated the parse error.
Err error // The raw error that precipitated this error, if any.
}
// String returns a human-readable error message.
func (e *ParseError) String() string {
return fmt.Sprintf("pkg parse: error parsing %q as int", e.Word)
}
// Parse parses the space-separated words in in put as integers.
func Parse(input string) (numbers []int, err error) {
defer func() {
if r := recover(); r != nil {
var ok bool
err, ok = r.(error)
if !ok {
err = fmt.Errorf("pkg: %v", r)
}
}
}()
fields := strings.Fields(input)
numbers = fields2numbers(fields)
return
}
func fields2numbers(fields []string) (numbers []int) {
if len(fields) == 0 {
panic("no words to parse")
}
for idx, field := range fields {
num, err := strconv.Atoi(field)
if err != nil {
panic(&ParseError{idx, field, err})
}
numbers = append(numbers, num)
}
return
}
// parse.go
package parse
import (
"fmt"
"strconv"
"strings"
)
// A ParseError indicates an error in converting a word into an integer.
type ParseError struct {
Index int // The index into the space-separated list of words.
Word string // The word that generated the parse error.
Err error // The raw error that precipitated this error, if any.
}
// String returns a human-readable error message.
func (e *ParseError) String() string {
return fmt.Sprintf("pkg parse: error parsing %q as int", e.Word)
}
// Parse parses the space-separated words in in put as integers.
func Parse(input string) (numbers []int, err error) {
defer func() {
if r := recover(); r != nil {
var ok bool
err, ok = r.(error)
if !ok {
err = fmt.Errorf("pkg: %v", r)
}
}
}()
fields := strings.Fields(input)
numbers = fields2numbers(fields)
return
}
func fields2numbers(fields []string) (numbers []int) {
if len(fields) == 0 {
panic("no words to parse")
}
for idx, field := range fields {
num, err := strconv.Atoi(field)
if err != nil {
panic(&ParseError{idx, field, err})
}
numbers = append(numbers, num)
}
return
}

70
eBook/examples/chapter_14/benchmark_channels.go
View File

@@ -1,35 +1,35 @@
package main
import (
"fmt"
"testing"
)
func main() {
fmt.Println(" sync", testing.Benchmark(BenchmarkChannelSync).String())
fmt.Println("buffered", testing.Benchmark(BenchmarkChannelBuffered).String())
}
func BenchmarkChannelSync(b *testing.B) {
ch := make(chan int)
go func() {
for i := 0; i < b.N; i++ {
ch <- i
}
close(ch)
}()
for _ = range ch {
}
}
func BenchmarkChannelBuffered(b *testing.B) {
ch := make(chan int, 128)
go func() {
for i := 0; i < b.N; i++ {
ch <- i
}
close(ch)
}()
for _ = range ch {
}
}
package main
import (
"fmt"
"testing"
)
func main() {
fmt.Println(" sync", testing.Benchmark(BenchmarkChannelSync).String())
fmt.Println("buffered", testing.Benchmark(BenchmarkChannelBuffered).String())
}
func BenchmarkChannelSync(b *testing.B) {
ch := make(chan int)
go func() {
for i := 0; i < b.N; i++ {
ch <- i
}
close(ch)
}()
for range ch {
}
}
func BenchmarkChannelBuffered(b *testing.B) {
ch := make(chan int, 128)
go func() {
for i := 0; i < b.N; i++ {
ch <- i
}
close(ch)
}()
for range ch {
}
}

8
eBook/examples/chapter_14/chaining.go
View File

@@ -7,7 +7,7 @@ import (
var ngoroutine = flag.Int("n", 100000, "how many goroutines")
func f(left, right chan int) { left <- 1+<-right }
func f(left, right chan int) { left <- 1 + <-right }
func main() {
flag.Parse()
@@ -17,7 +17,7 @@ func main() {
left, right = right, make(chan int)
go f(left, right)
}
right <- 0 // bang!
x := <-leftmost // wait for completion
fmt.Println(x) // 100000, ongeveer 1,5 s
right <- 0 // bang!
x := <-leftmost // wait for completion
fmt.Println(x) // 100000, ongeveer 1,5 s
}

31
eBook/examples/chapter_14/channel_block.go
View File

@@ -1,16 +1,15 @@
package main
import "fmt"
func main() {
ch1 := make(chan int)
go pump(ch1) // pump hangs
fmt.Println(<-ch1) // prints only 0
}
func pump(ch chan int) {
for i := 0; ; i++ {
ch <- i
}
}
package main
import "fmt"
func main() {
ch1 := make(chan int)
go pump(ch1) // pump hangs
fmt.Println(<-ch1) // prints only 0
}
func pump(ch chan int) {
for i := 0; ; i++ {
ch <- i
}
}

50
eBook/examples/chapter_14/channel_block2.go
View File

@@ -1,25 +1,25 @@
package main
import (
"fmt"
"time"
)
func main() {
ch1 := make(chan int)
go pump(ch1)
go suck(ch1) // tons of numbers appear
time.Sleep(1e9)
}
func pump(ch chan int) {
for i := 0; ; i++ {
ch <- i
}
}
func suck(ch chan int) {
for {
fmt.Println(<-ch)
}
}
package main
import (
"fmt"
"time"
)
func main() {
ch1 := make(chan int)
go pump(ch1)
go suck(ch1) // tons of numbers appear
time.Sleep(1e9)
}
func pump(ch chan int) {
for i := 0; ; i++ {
ch <- i
}
}
func suck(ch chan int) {
for {
fmt.Println(<-ch)
}
}

58
eBook/examples/chapter_14/channel_idiom2.go
View File

@@ -1,29 +1,29 @@
package main
import (
"fmt"
"time"
)
func main() {
suck(pump())
time.Sleep(1e9)
}
func pump() chan int {
ch := make(chan int)
go func() {
for i := 0; ; i++ {
ch <- i
}
}()
return ch
}
func suck(ch chan int) {
go func() {
for v := range ch {
fmt.Println(v)
}
}()
}
package main
import (
"fmt"
"time"
)
func main() {
suck(pump())
time.Sleep(1e9)
}
func pump() chan int {
ch := make(chan int)
go func() {
for i := 0; ; i++ {
ch <- i
}
}()
return ch
}
func suck(ch chan int) {
go func() {
for v := range ch {
fmt.Println(v)
}
}()
}

109
eBook/examples/chapter_14/conc_access.go
View File

@@ -1,54 +1,55 @@
// conc_access.go
package main
import (
"fmt"
"strconv"
)
type Person struct {
Name string
salary float64
chF chan func()
}
func NewPerson(name string, salary float64) *Person {
p := &Person{name, salary, make(chan func())}
go p.backend()
return p
}
func (p *Person) backend() {
for f := range p.chF {
f()
}
}
// Set salary.
func (p *Person) SetSalary(sal float64) {
p.chF <- func() { p.salary = sal }
}
// Retrieve salary.
func (p *Person) Salary() float64 {
fChan := make(chan float64)
p.chF <- func() { fChan <- p.salary }
return <-fChan
}
func (p *Person) String() string {
return "Person - name is: " + p.Name + " - salary is: " + strconv.FormatFloat(p.Salary(), 'f', 2, 64)
}
func main() {
bs := NewPerson("Smith Bill", 2500.5)
fmt.Println(bs)
bs.SetSalary(4000.25)
fmt.Println("Salary changed:")
fmt.Println(bs)
}
/* Output:
Person - name is: Smith Bill - salary is: 2500.50
Salary changed:
Person - name is: Smith Bill - salary is: 4000.25
*/
// conc_access.go
package main
import (
"fmt"
"strconv"
)
type Person struct {
Name string
salary float64
chF chan func()
}
func NewPerson(name string, salary float64) *Person {
p := &Person{name, salary, make(chan func())}
go p.backend()
return p
}
func (p *Person) backend() {
for f := range p.chF {
f()
}
}
// Set salary.
func (p *Person) SetSalary(sal float64) {
p.chF <- func() { p.salary = sal }
}
// Retrieve salary.
func (p *Person) Salary() float64 {
fChan := make(chan float64)
p.chF <- func() { fChan <- p.salary }
return <-fChan
}
func (p *Person) String() string {
return "Person - name is: " + p.Name + " - salary is: " + strconv.FormatFloat(p.Salary(), 'f', 2, 64)
}
func main() {
bs := NewPerson("Smith Bill", 2500.5)
fmt.Println(bs)
bs.SetSalary(4000.25)
fmt.Println("Salary changed:")
fmt.Println(bs)
}
/* Output:
Person - name is: Smith Bill - salary is: 2500.50
Salary changed:
Person - name is: Smith Bill - salary is: 4000.25
*/

115
eBook/examples/chapter_14/general_lazy_evalution1.go
View File

@@ -1,57 +1,58 @@
package main
import (
"fmt"
)
type Any interface{}
type EvalFunc func(Any) (Any, Any)
func main() {
evenFunc := func(state Any) (Any, Any) {
os := state.(int)
ns := os + 2
return os, ns
}
even := BuildLazyIntEvaluator(evenFunc, 0)
for i := 0; i < 10; i++ {
fmt.Printf("%vth even: %v\n", i, even())
}
}
func BuildLazyEvaluator(evalFunc EvalFunc, initState Any) func() Any {
retValChan := make(chan Any)
loopFunc := func() {
var actState Any = initState
var retVal Any
for {
retVal, actState = evalFunc(actState)
retValChan <- retVal
}
}
retFunc := func() Any {
return <-retValChan
}
go loopFunc()
return retFunc
}
func BuildLazyIntEvaluator(evalFunc EvalFunc, initState Any) func() int {
ef := BuildLazyEvaluator(evalFunc, initState)
return func() int {
return ef().(int)
}
}
/* Output:
0th even: 0
1th even: 2
2th even: 4
3th even: 6
4th even: 8
5th even: 10
6th even: 12
7th even: 14
8th even: 16
9th even: 18
*/
package main
import (
"fmt"
)
type Any interface{}
type EvalFunc func(Any) (Any, Any)
func main() {
evenFunc := func(state Any) (Any, Any) {
os := state.(int)
ns := os + 2
return os, ns
}
even := BuildLazyIntEvaluator(evenFunc, 0)
for i := 0; i < 10; i++ {
fmt.Printf("%vth even: %v\n", i, even())
}
}
func BuildLazyEvaluator(evalFunc EvalFunc, initState Any) func() Any {
retValChan := make(chan Any)
loopFunc := func() {
var actState Any = initState
var retVal Any
for {
retVal, actState = evalFunc(actState)
retValChan <- retVal
}
}
retFunc := func() Any {
return <-retValChan
}
go loopFunc()
return retFunc
}
func BuildLazyIntEvaluator(evalFunc EvalFunc, initState Any) func() int {
ef := BuildLazyEvaluator(evalFunc, initState)
return func() int {
return ef().(int)
}
}
/* Output:
0th even: 0
1th even: 2
2th even: 4
3th even: 6
4th even: 8
5th even: 10
6th even: 12
7th even: 14
8th even: 16
9th even: 18
*/

58
eBook/examples/chapter_14/goroutine1.go
View File

@@ -1,29 +1,29 @@
package main
import (
"fmt"
"time"
)
func main() {
fmt.Println("In main()")
// longWait()
go longWait()
// shortWait()
go shortWait()
fmt.Println("About to sleep in main()")
time.Sleep(10 * 1e9) // sleep works with a Duration in nanoseconds (ns) !
fmt.Println("At the end of main()")
}
func longWait() {
fmt.Println("Beginning longWait()")
time.Sleep(5 * 1e9) // sleep for 5 seconds
fmt.Println("End of longWait()")
}
func shortWait() {
fmt.Println("Beginning shortWait()")
time.Sleep(2 * 1e9) // sleep for 2 seconds
fmt.Println("End of shortWait()")
}
package main
import (
"fmt"
"time"
)
func main() {
fmt.Println("In main()")
// longWait()
go longWait()
// shortWait()
go shortWait()
fmt.Println("About to sleep in main()")
time.Sleep(10 * 1e9) // sleep works with a Duration in nanoseconds (ns) !
fmt.Println("At the end of main()")
}
func longWait() {
fmt.Println("Beginning longWait()")
time.Sleep(5 * 1e9) // sleep for 5 seconds
fmt.Println("End of longWait()")
}
func shortWait() {
fmt.Println("Beginning shortWait()")
time.Sleep(2 * 1e9) // sleep for 2 seconds
fmt.Println("End of shortWait()")
}

67
eBook/examples/chapter_14/goroutine2.go
View File

@@ -1,33 +1,34 @@
package main
import (
"fmt"
"time"
)
func main() {
ch := make(chan string)
go sendData(ch)
go getData(ch)
time.Sleep(1e9)
}
func sendData(ch chan string) {
ch <- "Washington"
ch <- "Tripoli"
ch <- "London"
ch <- "Beijing"
ch <- "Tokio"
}
func getData(ch chan string) {
var input string
// time.Sleep(1e9)
for {
input = <-ch
fmt.Printf("%s ", input)
}
}
// Washington Tripoli London Beijing Tokio
package main
import (
"fmt"
"time"
)
func main() {
ch := make(chan string)
go sendData(ch)
go getData(ch)
time.Sleep(1e9)
}
func sendData(ch chan string) {
ch <- "Washington"
ch <- "Tripoli"
ch <- "London"
ch <- "Beijing"
ch <- "Tokio"
}
func getData(ch chan string) {
var input string
// time.Sleep(1e9)
for {
input = <-ch
fmt.Printf("%s ", input)
}
}
// Washington Tripoli London Beijing Tokio

59
eBook/examples/chapter_14/goroutine3.go
View File

@@ -1,29 +1,30 @@
package main
import "fmt"
func main() {
ch := make(chan string)
go sendData(ch)
getData(ch)
}
func sendData(ch chan string) {
ch <- "Washington"
ch <- "Tripoli"
ch <- "London"
ch <- "Beijing"
ch <- "Tokio"
close(ch)
}
func getData(ch chan string) {
for {
input, open := <-ch
if !open {
break
}
fmt.Printf("%s ", input)
}
}
// Washington Tripoli London Beijing Tokio
package main
import "fmt"
func main() {
ch := make(chan string)
go sendData(ch)
getData(ch)
}
func sendData(ch chan string) {
ch <- "Washington"
ch <- "Tripoli"
ch <- "London"
ch <- "Beijing"
ch <- "Tokio"
close(ch)
}
func getData(ch chan string) {
for {
input, open := <-ch
if !open {
break
}
fmt.Printf("%s ", input)
}
}
// Washington Tripoli London Beijing Tokio

80
eBook/examples/chapter_14/goroutine_select.go
View File

@@ -1,40 +1,40 @@
package main
import (
"fmt"
"time"
)
func main() {
ch1 := make(chan int)
ch2 := make(chan int)
go pump1(ch1)
go pump2(ch2)
go suck(ch1, ch2)
time.Sleep(1e9)
}
func pump1(ch chan int) {
for i := 0; ; i++ {
ch <- i * 2
}
}
func pump2(ch chan int) {
for i := 0; ; i++ {
ch <- i + 5
}
}
func suck(ch1, ch2 chan int) {
for {
select {
case v := <-ch1:
fmt.Printf("Received on channel 1: %d\n", v)
case v := <-ch2:
fmt.Printf("Received on channel 2: %d\n", v)
}
}
}
package main
import (
"fmt"
"time"
)
func main() {
ch1 := make(chan int)
ch2 := make(chan int)
go pump1(ch1)
go pump2(ch2)
go suck(ch1, ch2)
time.Sleep(1e9)
}
func pump1(ch chan int) {
for i := 0; ; i++ {
ch <- i * 2
}
}
func pump2(ch chan int) {
for i := 0; ; i++ {
ch <- i + 5
}
}
func suck(ch1, ch2 chan int) {
for {
select {
case v := <-ch1:
fmt.Printf("Received on channel 1: %d\n", v)
case v := <-ch2:
fmt.Printf("Received on channel 2: %d\n", v)
}
}
}

96
eBook/examples/chapter_14/goroutine_select2.go
View File

@@ -1,49 +1,47 @@
package main
import (
"fmt"
"time"
"runtime"
)
func main() {
// setting GOMAXPROCS to 2 gives +- 22% performance increase,
// but increasing the number doesn't increase the performance
// without GOMAXPROCS: +- 86000
// setting GOMAXPROCS to 2: +- 105000
// setting GOMAXPROCS to 3: +- 94000
runtime.GOMAXPROCS(2)
ch1 := make(chan int)
ch2 := make(chan int)
go pump1(ch1)
go pump2(ch2)
go suck(ch1, ch2)
time.Sleep(1e9)
}
func pump1(ch chan int) {
for i:=0; ; i++ {
ch <- i*2
}
}
func pump2(ch chan int) {
for i:=0; ; i++ {
ch <- i+5
}
}
func suck(ch1,ch2 chan int) {
for i := 0; ; i++ {
select {
case v := <- ch1:
fmt.Printf("%d - Received on channel 1: %d\n", i, v)
case v := <- ch2:
fmt.Printf("%d - Received on channel 2: %d\n", i, v)
}
}
}
package main
import (
"fmt"
"runtime"
"time"
)
func main() {
// setting GOMAXPROCS to 2 gives +- 22% performance increase,
// but increasing the number doesn't increase the performance
// without GOMAXPROCS: +- 86000
// setting GOMAXPROCS to 2: +- 105000
// setting GOMAXPROCS to 3: +- 94000
runtime.GOMAXPROCS(2)
ch1 := make(chan int)
ch2 := make(chan int)
go pump1(ch1)
go pump2(ch2)
go suck(ch1, ch2)
time.Sleep(1e9)
}
func pump1(ch chan int) {
for i := 0; ; i++ {
ch <- i * 2
}
}
func pump2(ch chan int) {
for i := 0; ; i++ {
ch <- i + 5
}
}
func suck(ch1, ch2 chan int) {
for i := 0; ; i++ {
select {
case v := <-ch1:
fmt.Printf("%d - Received on channel 1: %d\n", i, v)
case v := <-ch2:
fmt.Printf("%d - Received on channel 2: %d\n", i, v)
}
}
}

60
eBook/examples/chapter_14/lazy_evaluation.go
View File

@@ -1,30 +1,30 @@
// lazy_evaluation.go
package main
import (
"fmt"
)
var resume chan int
func integers() chan int {
yield := make (chan int)
count := 0
go func () {
for {
yield <- count
count++
}
} ()
return yield
}
func generateInteger() int {
return <-resume
}
func main() {
resume = integers()
fmt.Println(generateInteger()) //=> 0
fmt.Println(generateInteger()) //=> 1
fmt.Println(generateInteger()) //=> 2
}
// lazy_evaluation.go
package main
import (
"fmt"
)
var resume chan int
func integers() chan int {
yield := make(chan int)
count := 0
go func() {
for {
yield <- count
count++
}
}()
return yield
}
func generateInteger() int {
return <-resume
}
func main() {
resume = integers()
fmt.Println(generateInteger()) //=> 0
fmt.Println(generateInteger()) //=> 1
fmt.Println(generateInteger()) //=> 2
}

63
eBook/examples/chapter_14/max_tasks.go
View File

@@ -1,31 +1,32 @@
package main
const MAXREQS = 50
var sem = make(chan int, MAXREQS)
type Request struct {
a, b int
replyc chan int
}
func process(r *Request) {
// do something
}
func handle(r *Request) {
sem <- 1 // doesn't matter what we put in it
process(r)
<-sem // one empty place in the buffer: the next request can start
}
func server(service chan *Request) {
for {
request := <-service
go handle(request)
}
}
func main() {
service := make(chan *Request)
go server(service)
}
package main
const MAXREQS = 50
var sem = make(chan int, MAXREQS)
type Request struct {
a, b int
replyc chan int
}
func process(r *Request) {
// do something
}
func handle(r *Request) {
sem <- 1 // doesn't matter what we put in it
process(r)
<-sem // one empty place in the buffer: the next request can start
}
func server(service chan *Request) {
for {
request := <-service
go handle(request)
}
}
func main() {
service := make(chan *Request)
go server(service)
}

106
eBook/examples/chapter_14/multiplex_server.go
View File

@@ -1,53 +1,53 @@
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package main
import "fmt"
type Request struct {
a, b int
replyc chan int // reply channel inside the Request
}
type binOp func(a, b int) int
func run(op binOp, req *Request) {
req.replyc <- op(req.a, req.b)
}
func server(op binOp, service chan *Request) {
for {
req := <-service // requests arrive here
// start goroutine for request:
go run(op, req) // don't wait for op
}
}
func startServer(op binOp) chan *Request {
reqChan := make(chan *Request)
go server(op, reqChan)
return reqChan
}
func main() {
adder := startServer(func(a, b int) int { return a + b })
const N = 100
var reqs [N]Request
for i := 0; i < N; i++ {
req := &reqs[i]
req.a = i
req.b = i + N
req.replyc = make(chan int)
adder <- req
}
// checks:
for i := N - 1; i >= 0; i-- { // doesn't matter what order
if <-reqs[i].replyc != N+2*i {
fmt.Println("fail at", i)
} else {
fmt.Println("Request ", i, " is ok!")
}
}
fmt.Println("done")
}
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package main
import "fmt"
type Request struct {
a, b int
replyc chan int // reply channel inside the Request
}
type binOp func(a, b int) int
func run(op binOp, req *Request) {
req.replyc <- op(req.a, req.b)
}
func server(op binOp, service chan *Request) {
for {
req := <-service // requests arrive here
// start goroutine for request:
go run(op, req) // don't wait for op
}
}
func startServer(op binOp) chan *Request {
reqChan := make(chan *Request)
go server(op, reqChan)
return reqChan
}
func main() {
adder := startServer(func(a, b int) int { return a + b })
const N = 100
var reqs [N]Request
for i := 0; i < N; i++ {
req := &reqs[i]
req.a = i
req.b = i + N
req.replyc = make(chan int)
adder <- req
}
// checks:
for i := N - 1; i >= 0; i-- { // doesn't matter what order
if <-reqs[i].replyc != N+2*i {
fmt.Println("fail at", i)
} else {
fmt.Println("Request ", i, " is ok!")
}
}
fmt.Println("done")
}

116
eBook/examples/chapter_14/multiplex_server2.go
View File

@@ -1,58 +1,58 @@
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package main
import "fmt"
type Request struct {
a, b int
replyc chan int // reply channel inside the Request
}
type binOp func(a, b int) int
func run(op binOp, req *Request) {
req.replyc <- op(req.a, req.b)
}
func server(op binOp, service chan *Request, quit chan bool) {
for {
select {
case req := <-service:
go run(op, req)
case <-quit:
return
}
}
}
func startServer(op binOp) (service chan *Request, quit chan bool) {
service = make(chan *Request)
quit = make(chan bool)
go server(op, service, quit)
return service, quit
}
func main() {
adder, quit := startServer(func(a, b int) int { return a + b })
const N = 100
var reqs [N]Request
for i := 0; i < N; i++ {
req := &reqs[i]
req.a = i
req.b = i + N
req.replyc = make(chan int)
adder <- req
}
// checks:
for i := N - 1; i >= 0; i-- { // doesn't matter what order
if <-reqs[i].replyc != N+2*i {
fmt.Println("fail at", i)
} else {
fmt.Println("Request ", i, " is ok!")
}
}
quit <- true
fmt.Println("done")
}
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package main
import "fmt"
type Request struct {
a, b int
replyc chan int // reply channel inside the Request
}
type binOp func(a, b int) int
func run(op binOp, req *Request) {
req.replyc <- op(req.a, req.b)
}
func server(op binOp, service chan *Request, quit chan bool) {
for {
select {
case req := <-service:
go run(op, req)
case <-quit:
return
}
}
}
func startServer(op binOp) (service chan *Request, quit chan bool) {
service = make(chan *Request)
quit = make(chan bool)
go server(op, service, quit)
return service, quit
}
func main() {
adder, quit := startServer(func(a, b int) int { return a + b })
const N = 100
var reqs [N]Request
for i := 0; i < N; i++ {
req := &reqs[i]
req.a = i
req.b = i + N
req.replyc = make(chan int)
adder <- req
}
// checks:
for i := N - 1; i >= 0; i-- { // doesn't matter what order
if <-reqs[i].replyc != N+2*i {
fmt.Println("fail at", i)
} else {
fmt.Println("Request ", i, " is ok!")
}
}
quit <- true
fmt.Println("done")
}

74
eBook/examples/chapter_14/sieve1.go
View File

@@ -1,37 +1,37 @@
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.package main
package main
import "fmt"
// Send the sequence 2, 3, 4, ... to channel 'ch'.
func generate(ch chan int) {
for i := 2; ; i++ {
ch <- i // Send 'i' to channel 'ch'.
}
}
// Copy the values from channel 'in' to channel 'out',
// removing those divisible by 'prime'.
func filter(in, out chan int, prime int) {
for {
i := <-in // Receive value of new variable 'i' from 'in'.
if i%prime != 0 {
out <- i // Send 'i' to channel 'out'.
}
}
}
// The prime sieve: Daisy-chain filter processes together.
func main() {
ch := make(chan int) // Create a new channel.
go generate(ch) // Start generate() as a goroutine.
for {
prime := <-ch
fmt.Print(prime, " ")
ch1 := make(chan int)
go filter(ch, ch1, prime)
ch = ch1
}
}
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.package main
package main
import "fmt"
// Send the sequence 2, 3, 4, ... to channel 'ch'.
func generate(ch chan int) {
for i := 2; ; i++ {
ch <- i // Send 'i' to channel 'ch'.
}
}
// Copy the values from channel 'in' to channel 'out',
// removing those divisible by 'prime'.
func filter(in, out chan int, prime int) {
for {
i := <-in // Receive value of new variable 'i' from 'in'.
if i%prime != 0 {
out <- i // Send 'i' to channel 'out'.
}
}
}
// The prime sieve: Daisy-chain filter processes together.
func main() {
ch := make(chan int) // Create a new channel.
go generate(ch) // Start generate() as a goroutine.
for {
prime := <-ch
fmt.Print(prime, " ")
ch1 := make(chan int)
go filter(ch, ch1, prime)
ch = ch1
}
}

106
eBook/examples/chapter_14/sieve2.go
View File

@@ -1,53 +1,53 @@
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package main
import (
"fmt"
)
// Send the sequence 2, 3, 4, ... to returned channel
func generate() chan int {
ch := make(chan int)
go func() {
for i := 2; ; i++ {
ch <- i
}
}()
return ch
}
// Filter out input values divisible by 'prime', send rest to returned channel
func filter(in chan int, prime int) chan int {
out := make(chan int)
go func() {
for {
if i := <-in; i%prime != 0 {
out <- i
}
}
}()
return out
}
func sieve() chan int {
out := make(chan int)
go func() {
ch := generate()
for {
prime := <-ch
ch = filter(ch, prime)
out <- prime
}
}()
return out
}
func main() {
primes := sieve()
for {
fmt.Println(<-primes)
}
}
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package main
import (
"fmt"
)
// Send the sequence 2, 3, 4, ... to returned channel
func generate() chan int {
ch := make(chan int)
go func() {
for i := 2; ; i++ {
ch <- i
}
}()
return ch
}
// Filter out input values divisible by 'prime', send rest to returned channel
func filter(in chan int, prime int) chan int {
out := make(chan int)
go func() {
for {
if i := <-in; i%prime != 0 {
out <- i
}
}
}()
return out
}
func sieve() chan int {
out := make(chan int)
go func() {
ch := generate()
for {
prime := <-ch
ch = filter(ch, prime)
out <- prime
}
}()
return out
}
func main() {
primes := sieve()
for {
fmt.Println(<-primes)
}
}

85
eBook/examples/chapter_14/timer_goroutine.go
View File

@@ -1,42 +1,43 @@
// default.go
package main
import (
"fmt"
"time"
)
func main() {
tick := time.Tick(1e8)
boom := time.After(5e8)
for {
select {
case <-tick:
fmt.Println("tick.")
case <-boom:
fmt.Println("BOOM!")
return
default:
fmt.Println(" .")
time.Sleep(5e7)
}
}
}
/* Output:
.
.
tick.
.
.
tick.
.
.
tick.
.
.
tick.
.
.
tick.
BOOM!
*/
// default.go
package main
import (
"fmt"
"time"
)
func main() {
tick := time.Tick(1e8)
boom := time.After(5e8)
for {
select {
case <-tick:
fmt.Println("tick.")
case <-boom:
fmt.Println("BOOM!")
return
default:
fmt.Println(" .")
time.Sleep(5e7)
}
}
}
/* Output:
.
.
tick.
.
.
tick.
.
.
tick.
.
.
tick.
.
.
tick.
BOOM!
*/

95
eBook/examples/chapter_16/closures_goroutines.go
View File

@@ -1,47 +1,48 @@
// closures_goroutines.go
package main
import (
"fmt"
"time"
)
var values = [5]int{10, 11, 12, 13, 14}
func main() {
// version A:
for ix := range values { // ix is index!
func() {
fmt.Print(ix, " ")
}() // call closure, prints each index
}
fmt.Println()
// version B: same as A, but call closure as a goroutine
for ix := range values {
go func() {
fmt.Print(ix, " ")
}()
}
time.Sleep(1e9)
// version C: the right way
for ix := range values {
go func(ix interface{}) {
fmt.Print(ix, " ")
}(ix)
}
time.Sleep(1e9)
// version D: print out the values:
for ix := range values {
val := values[ix]
go func() {
fmt.Print(val, " ")
}()
}
time.Sleep(1e9)
}
/* Output:
0 1 2 3 4
4 4 4 4 4
1 0 3 4 2
0 1 2 4 3
*/
// closures_goroutines.go
package main
import (
"fmt"
"time"
)
var values = [5]int{10, 11, 12, 13, 14}
func main() {
// version A:
for ix := range values { // ix is index!
func() {
fmt.Print(ix, " ")
}() // call closure, prints each index
}
fmt.Println()
// version B: same as A, but call closure as a goroutine
for ix := range values {
go func() {
fmt.Print(ix, " ")
}()
}
time.Sleep(1e9)
// version C: the right way
for ix := range values {
go func(ix interface{}) {
fmt.Print(ix, " ")
}(ix)
}
time.Sleep(1e9)
// version D: print out the values:
for ix := range values {
val := values[ix]
go func() {
fmt.Print(val, " ")
}()
}
time.Sleep(1e9)
}
/* Output:
0 1 2 3 4
4 4 4 4 4
1 0 3 4 2
0 1 2 4 3
*/

61
eBook/examples/chapter_16/pointer_interface.go
View File

@@ -1,31 +1,30 @@
// nexter.go
package main
import (
"fmt"
)
type nexter interface {
next() byte
}
func nextFew1(n nexter, num int) []byte {
var b []byte
for i:=0; i < num; i++ {
b[i] = n.next()
}
return b
}
func nextFew2(n *nexter, num int) []byte {
var b []byte
for i:=0; i < num; i++ {
b[i] = n.next() // compile error: n.next undefined (type *nexter has no field or method next)
}
return b
}
func main() {
fmt.Println("Hello World!")
}
// nexter.go
package main
import (
"fmt"
)
type nexter interface {
next() byte
}
func nextFew1(n nexter, num int) []byte {
var b []byte
for i := 0; i < num; i++ {
b[i] = n.next()
}
return b
}
func nextFew2(n *nexter, num int) []byte {
var b []byte
for i := 0; i < num; i++ {
b[i] = n.next() // compile error: n.next undefined (type *nexter has no field or method next)
}
return b
}
func main() {
fmt.Println("Hello World!")
}

2
eBook/examples/chapter_19/goto_v1/main.go
View File

@@ -11,6 +11,7 @@ URL: <input type="text" name="url">
<input type="submit" value="Add">
</form>
`
var store = NewURLStore()
func main() {
@@ -29,7 +30,6 @@ func Redirect(w http.ResponseWriter, r *http.Request) {
http.Redirect(w, r, url, http.StatusFound)
}
func Add(w http.ResponseWriter, r *http.Request) {
url := r.FormValue("url")
if url == "" {

4
eBook/examples/chapter_19/goto_v1/store.go
View File

@@ -3,8 +3,8 @@ package main
import "sync"
type URLStore struct {
urls map[string]string
mu sync.RWMutex
urls map[string]string
mu sync.RWMutex
}
func NewURLStore() *URLStore {

1
eBook/examples/chapter_19/goto_v2/main.go
View File

@@ -23,7 +23,6 @@ func Redirect(w http.ResponseWriter, r *http.Request) {
http.Redirect(w, r, url, http.StatusFound)
}
func Add(w http.ResponseWriter, r *http.Request) {
url := r.FormValue("url")
if url == "" {

8
eBook/examples/chapter_19/goto_v2/store.go
View File

@@ -9,9 +9,9 @@ import (
)
type URLStore struct {
urls map[string]string
mu sync.RWMutex
file *os.File
urls map[string]string
mu sync.RWMutex
file *os.File
}
type record struct {
@@ -70,7 +70,7 @@ func (s *URLStore) load() error {
if _, err := s.file.Seek(0, 0); err != nil {
return err
}
d := gob.NewDecoder(s.file)
d := gob.NewDecoder(s.file)
var err error
for err == nil {
var r record

20
eBook/examples/chapter_19/goto_v3/store.go
View File

@@ -1,7 +1,7 @@
package main
import (
// "bufio"
// "bufio"
"encoding/gob"
"io"
"log"
@@ -12,9 +12,9 @@ import (
const saveQueueLength = 1000
type URLStore struct {
urls map[string]string
mu sync.RWMutex
save chan record
urls map[string]string
mu sync.RWMutex
save chan record
}
type record struct {
@@ -74,9 +74,9 @@ func (s *URLStore) load(filename string) error {
}
defer f.Close()
// buffered reading:
// b := bufio.NewReader(f)
// d := gob.NewDecoder(b)
d := gob.NewDecoder(f)
// b := bufio.NewReader(f)
// d := gob.NewDecoder(b)
d := gob.NewDecoder(f)
for err == nil {
var r record
if err = d.Decode(&r); err == nil {
@@ -97,13 +97,13 @@ func (s *URLStore) saveLoop(filename string) {
log.Fatal("Error opening URLStore: ", err)
}
defer f.Close()
e := gob.NewEncoder(f)
e := gob.NewEncoder(f)
// buffered encoding:
// b := bufio.NewWriter(f)
// b := bufio.NewWriter(f)
// e := gob.NewEncoder(b)
// defer b.Flush()
for {
r := <-s.save // takes a record from the channel
r := <-s.save // takes a record from the channel
if err := e.Encode(r); err != nil {
log.Println("Error saving to URLStore: ", err)
}

12
eBook/examples/chapter_19/goto_v4/store.go
View File

@@ -11,9 +11,9 @@ import (
const saveQueueLength = 1000
type URLStore struct {
urls map[string]string
mu sync.RWMutex
save chan record
urls map[string]string
mu sync.RWMutex
save chan record
}
type record struct {
@@ -72,7 +72,7 @@ func (s *URLStore) load(filename string) error {
return err
}
defer f.Close()
d := json.NewDecoder(f)
d := json.NewDecoder(f)
for err == nil {
var r record
if err = d.Decode(&r); err == nil {
@@ -93,9 +93,9 @@ func (s *URLStore) saveLoop(filename string) {
log.Fatal("Error opening URLStore: ", err)
}
defer f.Close()
e := json.NewEncoder(f)
e := json.NewEncoder(f)
for {
r := <-s.save // takes a record from the channel
r := <-s.save // takes a record from the channel
if err := e.Encode(r); err != nil {
log.Println("Error saving to URLStore: ", err)
}

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