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Merge pull request #317 from appleboy/patch-3

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fix: coding style and file format for chapter 6.
This commit is contained in:
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2017-02-10 23:30:42 -05:00
committed by GitHub
parent d9041c7fc3 72c3839734
commit 759272e928
11 changed files with 290 additions and 279 deletions
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28
eBook/exercises/chapter_6/10to1_recursive.go
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@@ -1,13 +1,15 @@
package main
import "fmt"
func main() {
printrec(1)
}
func printrec(i int) {
if i>10 { return }
printrec(i+1)
fmt.Printf("%d ", i)
}
package main
import "fmt"
func main() {
printrec(1)
}
func printrec(i int) {
if i > 10 {
return
}
printrec(i + 1)
fmt.Printf("%d ", i)
}

34
eBook/exercises/chapter_6/compose.go
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@@ -1,17 +1,17 @@
// compose.go
package main
import (
"fmt"
"math"
)
func Compose(f, g func(x float64) float64) func(x float64) float64 {
return func(x float64) float64 { // closure
return f(g(x))
}
}
func main() {
fmt.Print(Compose(math.Sin, math.Cos)(0.5)) // output: 0.7691963548410085
}
// compose.go
package main
import (
"fmt"
"math"
)
func Compose(f, g func(x float64) float64) func(x float64) float64 {
return func(x float64) float64 { // closure
return f(g(x))
}
}
func main() {
fmt.Print(Compose(math.Sin, math.Cos)(0.5)) // output: 0.7691963548410085
}

113
eBook/exercises/chapter_6/error_returnval.go
View File

@@ -1,56 +1,57 @@
// error_returnval.go
package main
import (
"errors"
"fmt"
"math"
)
func main() {
fmt.Print("First example with -1: ")
ret1, err1 := MySqrt(-1)
if err1 != nil {
fmt.Println("Error! Return values are: ", ret1, err1)
} else {
fmt.Println("It's ok! Return values are: ", ret1, err1)
}
fmt.Print("Second example with 5: ")
//you could also write it like this
if ret2, err2 := MySqrt(5); err2 != nil {
fmt.Println("Error! Return values are: ", ret2, err2)
} else {
fmt.Println("It's ok! Return values are: ", ret2, err2)
}
// named return variables:
fmt.Println(MySqrt2(5))
}
func MySqrt(f float64) (float64, error) {
//return an error as second parameter if invalid input
if (f < 0) {
return float64(math.NaN()), errors.New("I won't be able to do a sqrt of negative number!")
}
//otherwise use default square root function
return math.Sqrt(f), nil
}
//name the return variables - by default it will have 'zero-ed' values i.e. numbers are 0, string is empty, etc.
func MySqrt2(f float64) (ret float64, err error) {
if (f < 0) {
//then you can use those variables in code
ret = float64(math.NaN())
err = errors.New("I won't be able to do a sqrt of negative number!")
} else {
ret = math.Sqrt(f)
//err is not assigned, so it gets default value nil
}
//automatically return the named return variables ret and err
return
}
/* Output:
First example with -1: Error! Return values are: NaN I won't be able to do a sqrt of negative number!
Second example with 5: It's ok! Return values are: 2.23606797749979 <nil>
2.23606797749979 <nil>
*/
// error_returnval.go
package main
import (
"errors"
"fmt"
"math"
)
func main() {
fmt.Print("First example with -1: ")
ret1, err1 := MySqrt(-1)
if err1 != nil {
fmt.Println("Error! Return values are: ", ret1, err1)
} else {
fmt.Println("It's ok! Return values are: ", ret1, err1)
}
fmt.Print("Second example with 5: ")
//you could also write it like this
if ret2, err2 := MySqrt(5); err2 != nil {
fmt.Println("Error! Return values are: ", ret2, err2)
} else {
fmt.Println("It's ok! Return values are: ", ret2, err2)
}
// named return variables:
fmt.Println(MySqrt2(5))
}
func MySqrt(f float64) (float64, error) {
//return an error as second parameter if invalid input
if f < 0 {
return float64(math.NaN()), errors.New("I won't be able to do a sqrt of negative number!")
}
//otherwise use default square root function
return math.Sqrt(f), nil
}
//name the return variables - by default it will have 'zero-ed' values i.e. numbers are 0, string is empty, etc.
func MySqrt2(f float64) (ret float64, err error) {
if f < 0 {
//then you can use those variables in code
ret = float64(math.NaN())
err = errors.New("I won't be able to do a sqrt of negative number!")
} else {
ret = math.Sqrt(f)
//err is not assigned, so it gets default value nil
}
//automatically return the named return variables ret and err
return
}
/* Output:
First example with -1: Error! Return values are: NaN I won't be able to do a sqrt of negative number!
Second example with 5: It's ok! Return values are: 2.23606797749979 <nil>
2.23606797749979 <nil>
*/

68
eBook/exercises/chapter_6/factorial.go
View File

@@ -1,34 +1,34 @@
// factorial.go
package main
import (
"fmt"
)
func main() {
for i := uint64(0); i < uint64(30); i++ {
fmt.Printf("Factorial of %d is %d\n", i, Factorial(i))
}
}
/* unnamed return variables:
func Factorial(n uint64) uint64 {
if n > 0 {
return n * Factorial(n-1)
}
return 1
}
*/
// named return variables:
func Factorial(n uint64) (fac uint64) {
fac = 1
if n > 0 {
fac = n * Factorial(n-1)
return
}
return
}
// int: correct results till 12!
// uint64: correct results till 21!
// factorial.go
package main
import (
"fmt"
)
func main() {
for i := uint64(0); i < uint64(30); i++ {
fmt.Printf("Factorial of %d is %d\n", i, Factorial(i))
}
}
/* unnamed return variables:
func Factorial(n uint64) uint64 {
if n > 0 {
return n * Factorial(n-1)
}
return 1
}
*/
// named return variables:
func Factorial(n uint64) (fac uint64) {
fac = 1
if n > 0 {
fac = n * Factorial(n-1)
return
}
return
}
// int: correct results till 12!
// uint64: correct results till 21!

48
eBook/exercises/chapter_6/fibonacci2.go
View File

@@ -1,24 +1,24 @@
package main
import "fmt"
func main() {
pos := 4
result, pos := fibonacci(pos)
fmt.Printf("the %d-th fibonacci number is: %d\n", pos, result)
pos = 10
result, pos = fibonacci(pos)
fmt.Printf("the %d-th fibonacci number is: %d\n", pos, result)
}
func fibonacci(n int) (val, pos int) {
if n <= 1 {
val = 1
} else {
v1, _ := fibonacci(n-1)
v2, _ := fibonacci(n-2)
val = v1 + v2
}
pos = n
return
}
package main
import "fmt"
func main() {
pos := 4
result, pos := fibonacci(pos)
fmt.Printf("the %d-th fibonacci number is: %d\n", pos, result)
pos = 10
result, pos = fibonacci(pos)
fmt.Printf("the %d-th fibonacci number is: %d\n", pos, result)
}
func fibonacci(n int) (val, pos int) {
if n <= 1 {
val = 1
} else {
v1, _ := fibonacci(n - 1)
v2, _ := fibonacci(n - 2)
val = v1 + v2
}
pos = n
return
}

40
eBook/exercises/chapter_6/fibonacci_closure.go
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@@ -1,20 +1,20 @@
package main
// fib returns a function that returns
// successive Fibonacci numbers.
func fib() func() int {
a, b := 1, 1
return func() int {
a, b = b, a+b
return b
}
}
func main() {
f := fib()
// Function calls are evaluated left-to-right.
// println(f(), f(), f(), f(), f())
for i:=0; i<=9; i++ {
println(i+2, f() )
}
}
package main
// fib returns a function that returns
// successive Fibonacci numbers.
func fib() func() int {
a, b := 1, 1
return func() int {
a, b = b, a+b
return b
}
}
func main() {
f := fib()
// Function calls are evaluated left-to-right.
// println(f(), f(), f(), f(), f())
for i := 0; i <= 9; i++ {
println(i+2, f())
}
}

74
eBook/exercises/chapter_6/function_filter2.go
View File

@@ -1,37 +1,37 @@
// function_filter2.go
package main
import "fmt"
type flt func(int) bool
// func isEven(n int) bool { if n%2 == 0 { return true }; return false }
func isEven(n int) bool {
if n%2 == 0 {
return true
}
return false
}
func filter(sl []int, f flt) (yes, no []int) {
for _, val := range sl {
if f(val) {
yes = append(yes, val)
} else {
no = append(no, val)
}
}
return
}
func main() {
slice := []int{1, 2, 3, 4, 5, 7}
fmt.Println("slice = ", slice)
even, odd := filter(slice, isEven)
fmt.Println("The even elements of slice are: ", even)
fmt.Println("The odd elements of slice are: ", odd)
}
/*
*/
// function_filter2.go
package main
import "fmt"
type flt func(int) bool
// func isEven(n int) bool { if n%2 == 0 { return true }; return false }
func isEven(n int) bool {
if n%2 == 0 {
return true
}
return false
}
func filter(sl []int, f flt) (yes, no []int) {
for _, val := range sl {
if f(val) {
yes = append(yes, val)
} else {
no = append(no, val)
}
}
return
}
func main() {
slice := []int{1, 2, 3, 4, 5, 7}
fmt.Println("slice = ", slice)
even, odd := filter(slice, isEven)
fmt.Println("The even elements of slice are: ", even)
fmt.Println("The odd elements of slice are: ", odd)
}
/*
*/

37
eBook/exercises/chapter_6/lambda_value.go
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@@ -1,18 +1,19 @@
// lambda_value.go
package main
import (
"fmt"
)
func main() {
fv := func() {
fmt.Println("Hello World!")
}
fv()
fmt.Printf("The type of fv is %T", fv)
}
/* Output:
Hello World!
The type of fv is func()
*/
// lambda_value.go
package main
import (
"fmt"
)
func main() {
fv := func() {
fmt.Println("Hello World!")
}
fv()
fmt.Printf("The type of fv is %T", fv)
}
/* Output:
Hello World!
The type of fv is func()
*/

49
eBook/exercises/chapter_6/mult_returnval.go
View File

@@ -1,24 +1,25 @@
// mult_returnval.go
package main
import (
"fmt"
)
func SumProductDiff(i, j int) (int, int, int) {
return i+j, i*j, i-j
}
func SumProductDiffN(i, j int) (s int, p int, d int) {
s, p, d = i+j, i*j, i-j
return
}
func main() {
sum, prod, diff := SumProductDiff(3,4)
fmt.Println("Sum:", sum, "| Product:",prod, "| Diff:", diff)
sum, prod, diff = SumProductDiffN(3,4)
fmt.Println("Sum:", sum, "| Product:",prod, "| Diff:", diff)
}
// Sum: 7 | Product: 12 | Diff: -1
// Sum: 7 | Product: 12 | Diff: -1
// mult_returnval.go
package main
import (
"fmt"
)
func SumProductDiff(i, j int) (int, int, int) {
return i + j, i * j, i - j
}
func SumProductDiffN(i, j int) (s int, p int, d int) {
s, p, d = i+j, i*j, i-j
return
}
func main() {
sum, prod, diff := SumProductDiff(3, 4)
fmt.Println("Sum:", sum, "| Product:", prod, "| Diff:", diff)
sum, prod, diff = SumProductDiffN(3, 4)
fmt.Println("Sum:", sum, "| Product:", prod, "| Diff:", diff)
}
// Sum: 7 | Product: 12 | Diff: -1
// Sum: 7 | Product: 12 | Diff: -1

32
eBook/exercises/chapter_6/strings_map.go
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@@ -1,13 +1,19 @@
// strings_map.go
package main
import (
"fmt"
"strings"
)
func main() {
asciiOnly := func(c rune) rune { if c > 127 { return ' ' }; return c }
fmt.Println(strings.Map(asciiOnly, "Jérôme Österreich"))
}
// J r me sterreich
// strings_map.go
package main
import (
"fmt"
"strings"
)
func main() {
asciiOnly := func(c rune) rune {
if c > 127 {
return ' '
}
return c
}
fmt.Println(strings.Map(asciiOnly, "Jérôme Österreich"))
}
// J r me sterreich

46
eBook/exercises/chapter_6/varargs.go
View File

@@ -1,23 +1,23 @@
// Q10_varargs.go
package main
import (
"fmt"
)
func main() {
printInts()
println()
printInts(2, 3)
println()
printInts(0, 1, 2, 3, 4, 5, 6, 7, 8, 9)
}
func printInts(list ...int) {
// for i:=0; i<len(list); i++ {
// fmt.Printf("%d\n", list[i])
// }
for _, v := range list {
fmt.Printf("%d\n", v)
}
}
// Q10_varargs.go
package main
import (
"fmt"
)
func main() {
printInts()
println()
printInts(2, 3)
println()
printInts(0, 1, 2, 3, 4, 5, 6, 7, 8, 9)
}
func printInts(list ...int) {
// for i:=0; i<len(list); i++ {
// fmt.Printf("%d\n", list[i])
// }
for _, v := range list {
fmt.Printf("%d\n", v)
}
}