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< ol class = "chapter" > < li class = "chapter-item expanded affix " > < a href = "../index.html" > Go语言圣经< / a > < / li > < li class = "chapter-item expanded affix " > < a href = "../preface.html" > 前言< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1.html" > < strong aria-hidden = "true" > 1.< / strong > 入门< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-01.html" > < strong aria-hidden = "true" > 1.1.< / strong > Hello, World< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-02.html" > < strong aria-hidden = "true" > 1.2.< / strong > 命令行参数< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-03.html" > < strong aria-hidden = "true" > 1.3.< / strong > 查找重复的行< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-04.html" > < strong aria-hidden = "true" > 1.4.< / strong > GIF动画< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-05.html" > < strong aria-hidden = "true" > 1.5.< / strong > 获取URL< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-06.html" > < strong aria-hidden = "true" > 1.6.< / strong > 并发获取多个URL< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-07.html" > < strong aria-hidden = "true" > 1.7.< / strong > Web服务< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch1/ch1-08.html" > < strong aria-hidden = "true" > 1.8.< / strong > 本章要点< / a > < / li > < / ol > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2.html" > < strong aria-hidden = "true" > 2.< / strong > 程序结构< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-01.html" > < strong aria-hidden = "true" > 2.1.< / strong > 命名< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-02.html" > < strong aria-hidden = "true" > 2.2.< / strong > 声明< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-03.html" > < strong aria-hidden = "true" > 2.3.< / strong > 变量< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-04.html" > < strong aria-hidden = "true" > 2.4.< / strong > 赋值< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-05.html" > < strong aria-hidden = "true" > 2.5.< / strong > 类型< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-06.html" > < strong aria-hidden = "true" > 2.6.< / strong > 包和文件< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch2/ch2-07.html" > < strong aria-hidden = "true" > 2.7.< / strong > 作用域< / a > < / li > < / ol > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3.html" > < strong aria-hidden = "true" > 3.< / strong > 基础数据类型< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-01.html" > < strong aria-hidden = "true" > 3.1.< / strong > 整型< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-02.html" > < strong aria-hidden = "true" > 3.2.< / strong > 浮点数< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-03.html" > < strong aria-hidden = "true" > 3.3.< / strong > 复数< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-04.html" > < strong aria-hidden = "true" > 3.4.< / strong > 布尔型< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-05.html" > < strong aria-hidden = "true" > 3.5.< / strong > 字符串< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch3/ch3-06.html" > < strong aria-hidden = "true" > 3.6.< / strong > 常量< / a > < / li > < / ol > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4.html" > < strong aria-hidden = "true" > 4.< / strong > 复合数据类型< / a > < / li > < li > < ol class = "section" > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-01.html" > < strong aria-hidden = "true" > 4.1.< / strong > 数组< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-02.html" > < strong aria-hidden = "true" > 4.2.< / strong > Slice< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-03.html" > < strong aria-hidden = "true" > 4.3.< / strong > Map< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-04.html" > < strong aria-hidden = "true" > 4.4.< / strong > 结构体< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-05.html" > < strong aria-hidden = "true" > 4.5.< / strong > JSON< / a > < / li > < li class = "chapter-item expanded " > < a href = "../ch4/ch4-06.html" > < strong aria-hidd
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2022-08-24 10:48:15 +00:00
< li > < em > KusonStack一站式可编程配置技术栈(Go): < a href = "https://github.com/KusionStack/kusion" > https://github.com/KusionStack/kusion< / a > < / em > < / li >
< li > < em > KCL 配置编程语言(Rust): < a href = "https://github.com/KusionStack/KCLVM" > https://github.com/KusionStack/KCLVM< / a > < / em > < / li >
< li > < em > 凹语言™: < a href = "https://github.com/wa-lang/wa" > https://github.com/wa-lang/wa< / a > < / em > < / li >
2022-08-04 06:59:33 +00:00
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< hr >
< h2 id = "124-示例-编码为s表达式" > < a class = "header" href = "#124-示例-编码为s表达式" > 12.4. 示例: 编码为S表达式< / a > < / h2 >
< p > Display是一个用于显示结构化数据的调试工具， < / p >
< p > 正如我们在4.5节中中看到的， ， ， ， < / p >
< p > 在本节中， ， ： < / p >
< pre > < code > 42 integer
" hello" string（ ）
foo symbol（ ）
(1 2 3) list （ ）
< / code > < / pre >
< p > 布尔型习惯上使用t符号表示true， ， ， ， < / p >
< p > 我们将Go语言的类型编码为S表达式的方法如下。整数和字符串以显而易见的方式编码。空值编码为nil符号。数组和slice被编码为列表。< / p >
< p > 结构体被编码为成员对象的列表， ， ， ， ， ， < / p >
< p > 编码是由一个encode递归函数完成， ： < / p >
< p > < u > < i > gopl.io/ch12/sexpr< / i > < / u > < / p >
< pre > < code class = "language-Go" > func encode(buf *bytes.Buffer, v reflect.Value) error {
switch v.Kind() {
case reflect.Invalid:
buf.WriteString(" nil" )
case reflect.Int, reflect.Int8, reflect.Int16,
reflect.Int32, reflect.Int64:
fmt.Fprintf(buf, " %d" , v.Int())
case reflect.Uint, reflect.Uint8, reflect.Uint16,
reflect.Uint32, reflect.Uint64, reflect.Uintptr:
fmt.Fprintf(buf, " %d" , v.Uint())
case reflect.String:
fmt.Fprintf(buf, " %q" , v.String())
case reflect.Ptr:
return encode(buf, v.Elem())
case reflect.Array, reflect.Slice: // (value ...)
buf.WriteByte('(')
for i := 0; i < v.Len(); i++ {
if i > 0 {
buf.WriteByte(' ')
}
if err := encode(buf, v.Index(i)); err != nil {
return err
}
}
buf.WriteByte(')')
case reflect.Struct: // ((name value) ...)
buf.WriteByte('(')
for i := 0; i < v.NumField(); i++ {
if i > 0 {
buf.WriteByte(' ')
}
fmt.Fprintf(buf, " (%s " , v.Type().Field(i).Name)
if err := encode(buf, v.Field(i)); err != nil {
return err
}
buf.WriteByte(')')
}
buf.WriteByte(')')
case reflect.Map: // ((key value) ...)
buf.WriteByte('(')
for i, key := range v.MapKeys() {
if i > 0 {
buf.WriteByte(' ')
}
buf.WriteByte('(')
if err := encode(buf, key); err != nil {
return err
}
buf.WriteByte(' ')
if err := encode(buf, v.MapIndex(key)); err != nil {
return err
}
buf.WriteByte(')')
}
buf.WriteByte(')')
default: // float, complex, bool, chan, func, interface
return fmt.Errorf(" unsupported type: %s" , v.Type())
}
return nil
}
< / code > < / pre >
< p > Marshal函数是对encode的包装， ： < / p >
< pre > < code class = "language-Go" > // Marshal encodes a Go value in S-expression form.
func Marshal(v interface{}) ([]byte, error) {
var buf bytes.Buffer
if err := encode(& buf, reflect.ValueOf(v)); err != nil {
return nil, err
}
return buf.Bytes(), nil
}
< / code > < / pre >
< p > 下面是Marshal对12.3节的strangelove变量编码后的结果： < / p >
< pre > < code > ((Title " Dr. Strangelove" ) (Subtitle " How I Learned to Stop Worrying and Lo
ve the Bomb" ) (Year 1964) (Actor ((" Grp. Capt. Lionel Mandrake" " Peter Sell
ers" ) (" Pres. Merkin Muffley" " Peter Sellers" ) (" Gen. Buck Turgidson" " Geor
ge C. Scott" ) (" Brig. Gen. Jack D. Ripper" " Sterling Hayden" ) (" Maj. T.J. \
" King\" Kong" " Slim Pickens" ) (" Dr. Strangelove" " Peter Sellers" ))) (Oscars
(" Best Actor (Nomin.)" " Best Adapted Screenplay (Nomin.)" " Best Director (N
omin.)" " Best Picture (Nomin.)" )) (Sequel nil))
< / code > < / pre >
< p > 整个输出编码为一行中以减少输出的大小， ； < / p >
< pre > < code > ((Title " Dr. Strangelove" )
(Subtitle " How I Learned to Stop Worrying and Love the Bomb" )
(Year 1964)
(Actor ((" Grp. Capt. Lionel Mandrake" " Peter Sellers" )
(" Pres. Merkin Muffley" " Peter Sellers" )
(" Gen. Buck Turgidson" " George C. Scott" )
(" Brig. Gen. Jack D. Ripper" " Sterling Hayden" )
(" Maj. T.J. \" King\" Kong" " Slim Pickens" )
(" Dr. Strangelove" " Peter Sellers" )))
(Oscars (" Best Actor (Nomin.)"
" Best Adapted Screenplay (Nomin.)"
" Best Director (Nomin.)"
" Best Picture (Nomin.)" ))
(Sequel nil))
< / code > < / pre >
< p > 和fmt.Print、json.Marshal、Display函数类似， < / p >
< p > 在12.6节中， ， ， < / p >
< p > < strong > 练习 12.3： < / strong > 实现encode函数缺少的分支。将布尔类型编码为t和nil， ， " []int" (1 2 3)） ， ： < / p >
< p > < strong > 练习 12.4： < / strong > 修改encode函数， < / p >
< p > < strong > 练习 12.5： < / strong > 修改encode函数， < / p >
< p > < strong > 练习 12.6： < / strong > 修改encode， ， < / p >
< p > < strong > 练习 12.7： < / strong > 创建一个基于流式的API， ， < / p >
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