learn(GoProgrammingFromBeginnerToMaster): 1-30

Author: jxs1211

.vscode/launch.json

@@ -0,0 +1,16 @@
+{
+    // Use IntelliSense to learn about possible attributes.
+    // Hover to view descriptions of existing attributes.
+    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "name": "Launch file",
+            "type": "go",
+            "request": "launch",
+            "mode": "debug",
+            "program": "${file}",
+            // "args": ["1.jpg"]
+        }
+    ]
+}

chapter3/sources/control_structure_idiom_3.go

@@ -12,6 +12,7 @@ func main() {
 
 	//byte sequence of s: 0xe4 0xb8 0xad 0xe5 0x9b 0xbd 0xe4 0xba 0xba
 	var sl = []byte{0xe4, 0xb8, 0xad, 0xe5, 0x9b, 0xbd, 0xe4, 0xba, 0xba}
+	fmt.Println(string(sl))
 	for _, v := range sl {
 		fmt.Printf("0x%x ", v)
 	}
@@ -20,7 +21,8 @@ func main() {
 	sl[3] = 0xd0
 	sl[4] = 0xd6
 	sl[5] = 0xb9
-
+	sl2 := []byte{0xd6, 0xb9}
+	fmt.Printf("%v - %v - %x - %b - %c\n", []rune(string(sl2)), string(sl2), sl2, sl2, sl2)
 	for i, v := range string(sl) {
 		fmt.Printf("%d %x\n", i, v)
 	}

chapter3/sources/control_structure_idiom_4.go

@@ -23,6 +23,7 @@ func main() {
 		fmt.Println(k, v)
 	}
 	fmt.Println("counter is ", counter)
+	fmt.Println("final:", m)
 	fmt.Println("\n")
 
 	m["tony"] = 21
@@ -36,4 +37,5 @@ func main() {
 		fmt.Println(k, v)
 	}
 	fmt.Println("counter is ", counter)
+	fmt.Println("final:", m)
 }

chapter3/sources/control_structure_idiom_6.go

@@ -5,17 +5,19 @@ import (
 	"time"
 )
 
-func main() {
+func ShowBreakAtWhere() {
 	exit := make(chan interface{})
 
 	go func() {
+		// loop:
 		for {
 			select {
 			case <-time.After(time.Second):
 				fmt.Println("tick")
 			case <-exit:
 				fmt.Println("exiting...")
-				break
+				// break loop
+				break // break outside the select, not the for
 			}
 		}
 		fmt.Println("exit!")
@@ -27,3 +29,32 @@ func main() {
 	// wait child goroutine exit
 	time.Sleep(3 * time.Second)
 }
+
+func ShowLabelLoop() {
+	final_sl := [][]int{}
+outLoop:
+	for i := 0; i < 10; i++ {
+		sl := []int{}
+		fmt.Printf("sl len: %d sl cap: %d\n", len(sl), cap(sl))
+		for j := 0; j < 10; j++ {
+			if i >= 5 {
+				break outLoop
+			}
+			if j >= 5 {
+				continue outLoop
+			}
+			// fmt.Printf("%d * %d = %d\n", i, j, i*j)
+			sl = append(sl, i*j)
+		}
+		fmt.Println(sl)
+		final_sl = append(final_sl, sl)
+	}
+	fmt.Println(final_sl)
+}
+
+func main() {
+	// ShowLabelLoop()
+	sl := []int{}
+	sl = append(sl, 1)
+	fmt.Println(sl)
+}

chapter3/sources/evaluation_order_8.go

@@ -33,14 +33,33 @@ func getANumToChannel() int {
 	return 2
 }
 
-func main() {
+func Show() {
 	select {
 	//recv from channel
 	case (getASlice())[0] = <-getAReadOnlyChannel():
 		fmt.Println("recv something from a readonly channel")
+		fmt.Println(getASlice())
 
 	//send to channel
 	case getAWriteOnlyChannel() <- getANumToChannel():
 		fmt.Println("send something to a writeonly channel")
 	}
 }
+
+func Show2(i int) {
+	switch i {
+	case 1:
+		fmt.Println(1)
+		fallthrough
+	case 2:
+		fmt.Println(2)
+		fallthrough
+	default:
+		fmt.Println(-1)
+	}
+}
+
+func main() {
+	i := 1
+	Show2(i)
+}

chapter3/sources/for_range_bench_test.go

@@ -2,42 +2,45 @@ package array_test
 
 import "testing"
 
-var a [100]int
+var a [10000]int
 var sl = a[:]
 
-func arrayRangeLoop() {
+func arrayLoop() {
+
 	var sum int
-	for _, n := range a {
-		sum += n
+	for _, v := range a {
+		sum += v
 	}
 }
 
-func pointerToArrayRangeLoop() {
+func arrayPointLoop() {
 	var sum int
-	for _, n := range &a {
-		sum += n
+	for _, v := range &a {
+		sum += v
 	}
 }
 
-func sliceRangeLoop() {
+func arraySliceLoop() {
 	var sum int
-	for _, n := range sl {
-		sum += n
+	for _, v := range sl {
+		sum += v
 	}
 }
 
-func BenchmarkArrayRangeLoop(b *testing.B) {
+func BenchmarkArrayLoop(b *testing.B) {
 	for i := 0; i < b.N; i++ {
-		arrayRangeLoop()
+		arrayLoop()
 	}
 }
-func BenchmarkPointerToArrayRangeLoop(b *testing.B) {
+
+func BenchmarkArrayPointLoop(b *testing.B) {
 	for i := 0; i < b.N; i++ {
-		pointerToArrayRangeLoop()
+		arrayPointLoop()
 	}
 }
-func BenchmarkSliceRangeLoop(b *testing.B) {
+
+func BenchmarkArraySliceLoop(b *testing.B) {
 	for i := 0; i < b.N; i++ {
-		sliceRangeLoop()
+		arraySliceLoop()
 	}
 }

chapter3/sources/item16-demo/chapter3-demo1/cmd/app2/main.go

@@ -1,7 +1,7 @@
 package main
 
 import (
-	mypkg2 "github.com/bigwhite/effective-go-book/chapter2-demo1/pkg/pkg2"
+	mypkg2 "github.com/bigwhite/effective-go-book/chapter3-demo1/pkg/pkg2"
 )
 
 func main() {

chapter3/sources/main.go

@@ -0,0 +1,80 @@
+package main
+
+import (
+	"fmt"
+	"reflect"
+)
+
+type Status uint32
+
+const (
+	Open Status = iota
+	Closed
+)
+
+func ShowNilInterface() {
+	var p *int
+	var i interface{} = p
+	if i == nil {
+		fmt.Println("i = nil")
+		return
+	}
+	fmt.Printf("%v != nil, type: %T,\n i's value: %v, i's type: %s\n", i, i, reflect.ValueOf(i), reflect.TypeOf(i).String())
+}
+
+type MyStruct struct {
+	Name     string
+	nickname string
+}
+
+func ShowFuncListIteration() {
+	type f func()
+
+	f1 := func() {
+		fmt.Println("call f1")
+	}
+
+	f2 := func() {
+		fmt.Println("call f2")
+	}
+	funcs := []f{f1, f2}
+	for _, v := range funcs {
+		v()
+	}
+
+	funcs_m := map[string]f{
+		"f1": f1,
+		"f2": f2,
+	}
+	for k, v := range funcs_m {
+		fmt.Println(k)
+		v()
+	}
+	funcs_m["f2"]()
+}
+
+func main() {
+	// fmt.Println("open: ", Open)
+	// var v *net.IPAddr
+	// fmt.Printf("v: %v\n", v)
+	// var b bytes.Buffer
+	// _, _ = b.Write([]byte("Hello"))
+	// fmt.Println(b.String())
+
+	// s := MyStruct{Name: "shen"}
+	// fmt.Printf("%#v\n", s)
+
+	// i := []int{'a': 1, 'b': 2}
+	// fmt.Printf("i: %#v cap: %d char b: %d\n", i, cap(i), 'b')
+	// m := map[string]int64{
+	// 	"us": int64(time.Nanosecond),
+	// 	// "us": int64(time.Nanosecond),
+	// 	"µs": int64(time.Microsecond), // U+00B5 = micro symbol
+	// 	"μs": int64(time.Microsecond),
+	// }
+
+	// fmt.Printf("%#v\n", m)
+	// fmt.Printf("%q == %q: %v\n", "µs", "µs", "µs" == "µs")
+
+	// ShowFuncListIteration()
+}

chapter3/sources/map_concurrent_read_and_write.go

@@ -31,9 +31,10 @@ func main() {
 
 	go func() {
 		for i := 0; i < 1000; i++ {
-			doWrite(m)
+			doIteration(m)
 		}
 	}()
-
+	p := m[1]
+	fmt.Println(p)
 	time.Sleep(5 * time.Second)
 }

chapter3/sources/map_multiple_iterate.go

@@ -20,4 +20,8 @@ func main() {
 	for i := 0; i < 3; i++ {
 		doIteration(m)
 	}
+
+	for k, _ := range m {
+		fmt.Println("k: ", k)
+	}
 }

chapter3/sources/map_stable_iterate.go

@@ -5,7 +5,7 @@ import "fmt"
 func doIteration(sl []int, m map[int]int) {
 	fmt.Printf("{ ")
 	for _, k := range sl {
-		v, ok := m[k]
+		v, ok := m[k] // keep the order
 		if !ok {
 			continue
 		}
@@ -25,7 +25,7 @@ func main() {
 	for k, _ := range m {
 		sl = append(sl, k)
 	}
-
+	fmt.Println(sl)
 	for i := 0; i < 3; i++ {
 		doIteration(sl, m)
 	}

chapter3/sources/string_for_range_covert_optimize.go

@@ -8,6 +8,7 @@ import (
 func convert() {
 	s := "中国欢迎您，北京欢迎您"
 	sl := []byte(s)
+	fmt.Println(string(sl))
 	for _, v := range sl {
 		_ = v
 	}
@@ -21,5 +22,5 @@ func convertWithOptimize() {
 
 func main() {
 	fmt.Println(testing.AllocsPerRun(1, convert))
-	fmt.Println(testing.AllocsPerRun(1, convertWithOptimize))
+	// fmt.Println(testing.AllocsPerRun(1, convertWithOptimize))
 }

chapter4/sources/1.jpg

@@ -1,6 +1,8 @@
 package main
 
-import "fmt"
+import (
+	"fmt"
+)
 
 func foo1() {
 	sl := []int{1, 2, 3}
@@ -11,6 +13,7 @@ func foo1() {
 	sl = []int{3, 2, 1}
 	_ = sl
 }
+
 func foo2() {
 	sl := []int{1, 2, 3}
 	defer func(p *[]int) {

chapter4/sources/deferred_func_8.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"fmt"
+)
+
+func trace(s string) string {
+	fmt.Println("enter: ", s)
+	return s
+}
+
+func un(s string) {
+	fmt.Println("leave: ", s)
+}
+
+func a() {
+	defer un(trace("a"))
+	fmt.Println("in: a")
+}
+
+func b() {
+	defer un(trace("b"))
+	fmt.Println("in: b")
+	a()
+}
+
+func main() {
+	b()
+}