feat: add map trap

.gitignore

@@ -1 +1,3 @@
-.idea
+.idea
+
+00-playground

05-options-pattern/main.go

@@ -1,27 +1,27 @@
-// package main
+package main
 
-// type Book struct {
-// 	Title string
-// 	ISBN  string
-// }
+type Book struct {
+	Title string
+	ISBN  string
+}
 
-// func NewBook(t string) *Book {
-// 	return &Book{
-// 		Title: t,
-// 		ISBN:  "",
-// 	}
-// }
+func NewBook(t string) *Book {
+	return &Book{
+		Title: t,
+		ISBN:  "",
+	}
+}
 
-// func NewBook2(t string, i string) *Book {
-// 	return &Book{
-// 		Title: t,
-// 		ISBN:  i,
-// 	}
-// }
+func NewBook2(t string, i string) *Book {
+	return &Book{
+		Title: t,
+		ISBN:  i,
+	}
+}
 
-// func main() {
-// 	_ = NewBook("早点下班的go语言学习法")
-// 	_ = NewBook2("早点下班的go语言学习法", "20230101")
-// }
+func main() {
+	_ = NewBook("早点下班的go语言学习法")
+	_ = NewBook2("早点下班的go语言学习法", "20230101")
+}
 
-// // How To Make Constructor Better
+// How To Make Constructor Better

05-options-pattern/options_way.go

@@ -1,27 +1,27 @@
 package main
 
-type Book struct {
+type Book___ struct {
 	Title string
 	Code  string
 }
-type Option func(*Book)
+type Option func(*Book___)
 
-func NewBook_(options ...Option) *Book {
-	b := &Book{}
+func NewBook_(options ...Option) *Book___ {
+	b := &Book___{}
 	for _, option := range options {
 		option(b)
 	}
 	return b
 }
 
 func WithTitle(title string) Option {
-	return func(b *Book) {
+	return func(b *Book___) {
 		b.Title = title
 	}
 }
 
 func WithISBN(ISBN string) Option {
-	return func(b *Book) {
+	return func(b *Book___) {
 		b.Code = ISBN
 	}
 }

06-range-expression/main.go

@@ -4,8 +4,18 @@ import "fmt"
 
 func main() {
 	s := []string{"something"}
-	for range s {
+	for i := 0; i < len(s); i++ {
 		s = append(s, "new_one")
+
 		fmt.Println(s)
 	}
 }
+
+// Which Output is correct:
+// A. [something new_one]
+
+// B. [something new_one],
+//    [something new_one new_one ]
+//    [something new_one new_one new_one] ...
+
+// C. panic: runtime error: index out of range

07-map-trap/main.go

@@ -0,0 +1,27 @@
+package main
+
+import "fmt"
+
+func main() {
+	m := map[string]int{
+		"rust": 1,
+		"go":   2,
+		"cpp":  3,
+	}
+	//copy one
+	m_copy := make(map[string]int, len(m))
+	for k, v := range m {
+		m_copy[k] = v
+	}
+
+	for k, v := range m_copy {
+		m[k+"_new"] = v + 100
+	}
+
+	fmt.Printf("map length: %d\n", len(m))
+}
+
+// Output
+// A: 3
+// B: 6
+// C: I don't know

07-map-trap/map_struct.go.fake

@@ -0,0 +1,35 @@
+//fake code
+
+package main
+
+type Map struct {
+	size    int
+	buckets []Bucket
+}
+type Bucket struct {
+	key   Key
+	value Value
+}
+
+func (m *Map) Set(key Key, value Value) {
+	// Compute the hash of the key.
+	hash := hashFunction(key)
+	// Determine the index of the bucket for this key.
+	index := hash % m.size
+	m.buckets[index] = Bucket{key: key, value: value}
+}
+
+func (m *Map) Get(key Key) (Value, bool) {
+	hash := hashFunction(key)
+	index := hash % m.size
+	// Retrieve the value for the key from the bucket.
+	if m.buckets[index].key == key {
+		return m.buckets[index].value, true
+	} else {
+		return Value{}, false
+	}
+}
+
+func hashFunction(key invalid type) {
+	panic("unimplemented")
+}

readme.md

@@ -19,7 +19,7 @@ Sharing is free but caring is priceless. [So, now please click here](https://www
 
   _好的习惯会给无聊代码带来一阵清风._
 
-* **[range后面的表达式]()**
+* **[你关注过range后面的表达式吗]()**
 
  _不同于for，range后接的表达式只会被求值一次._