add 08.2.md 08.3.md 08.4.md 08.5.md 08.6.md

eBook/examples/chapter_8/invert_map.go

@@ -0,0 +1,23 @@
+package main
+import (
+    "fmt"
+)
+
+var (
+    barVal = map[string]int{"alpha": 34, "bravo": 56, "charlie": 23,
+                            "delta": 87, "echo": 56, "foxtrot": 12,
+                            "golf": 34, "hotel": 16, "indio": 87,
+                            "juliet": 65, "kili": 43, "lima": 98}
+)
+
+func main() {
+    invMap := make(map[int]string, len(barVal))
+    for k, v := range barVal {
+        invMap[v] = k
+    }
+    fmt.Println("inverted:")
+    for k, v := range invMap {
+        fmt.Printf("Key: %v, Value: %v / ", k, v)
+    }
+    fmt.Println()
+}

eBook/examples/chapter_8/map_testelement.go

@@ -0,0 +1,31 @@
+package main
+import "fmt"
+
+func main() {
+    var value int
+    var isPresent bool
+
+    map1 := make(map[string]int)
+    map1["New Delhi"] = 55
+    map1["Beijing"] = 20
+    map1["Washington"] = 25
+    value, isPresent = map1["Beijing"]
+    if isPresent {
+        fmt.Printf("The value of \"Beijin\" in map1 is: %d\n", value)
+    } else {
+        fmt.Printf("map1 does not contain Beijing")
+    }
+
+    value, isPresent = map1["Paris"]
+    fmt.Printf("Is \"Paris\" in map1 ?: %t\n", isPresent)
+    fmt.Printf("Value is: %d\n", value)
+
+    // delete an item:
+    delete(map1, "Washington")
+    value, isPresent = map1["Washington"]
+    if isPresent {
+        fmt.Printf("The value of \"Washington\" in map1 is: %d\n", value)
+    } else {
+        fmt.Println("map1 does not contain Washington")
+    }
+}

eBook/examples/chapter_8/maps_forrange.go

@@ -0,0 +1,13 @@
+package main
+import "fmt"
+
+func main() {
+    map1 := make(map[int]float32)
+    map1[1] = 1.0
+    map1[2] = 2.0
+    map1[3] = 3.0
+    map1[4] = 4.0
+    for key, value := range map1 {
+        fmt.Printf("key is: %d - value is: %f\n", key, value)
+    }
+}

eBook/examples/chapter_8/slice_maps.go

@@ -0,0 +1,20 @@
+package main
+import "fmt"
+
+func main() {
+    // Version A:
+    items := make([]map[int]int, 5)
+    for i:= range items {
+        items[i] = make(map[int]int, 1)
+        items[i][1] = 2
+    }
+    fmt.Printf("Version A: Value of items: %v\n", items)
+
+    // Version B: NOT GOOD!
+    items2 := make([]map[int]int, 5)
+    for _, item := range items2 {
+        item = make(map[int]int, 1) // item is only a copy of the slice element.
+        item[1] = 2 // This 'item' will be lost on the next iteration.
+    }
+    fmt.Printf("Version B: Value of items: %v\n", items2)
+}

eBook/examples/chapter_8/sort_map.go

@@ -0,0 +1,32 @@
+// the telephone alphabet:
+package main
+import (
+    "fmt"
+    "sort"
+)
+
+var (
+    barVal = map[string]int{"alpha": 34, "bravo": 56, "charlie": 23,
+                            "delta": 87, "echo": 56, "foxtrot": 12,
+                            "golf": 34, "hotel": 16, "indio": 87,
+                            "juliet": 65, "kili": 43, "lima": 98}
+)
+
+func main() {
+    fmt.Println("unsorted:")
+    for k, v := range barVal {
+        fmt.Printf("Key: %v, Value: %v / ", k, v)
+    }
+    keys := make([]string, len(barVal))
+    i := 0
+    for k, _ := range barVal {
+        keys[i] = k
+        i++
+    }
+    sort.Strings(keys)
+    fmt.Println()
+    fmt.Println("sorted:")
+    for _, k := range keys {
+        fmt.Printf("Key: %v, Value: %v / ", k, barVal[k])
+    }
+}