Golang 泛型：[type T]，为啥要用中括号呢。。。

[viktor123]

传送门： https://blog.golang.org/generics-next-step

官方示例：

package main

import (
	"fmt"
)

// The playground now supports parentheses or square brackets (only one at
// a time) for generic type and function declarations and instantiations.
// By default, parentheses are expected. To switch to square brackets,
// the first generic declaration in the source must use square brackets.

func Print[type T](s []T) {
	for _, v := range s {
		fmt.Print(v)
	}
}

func main() {
	Print([]string{"Hello, ", "playground\n"})
}

High Level Overview：

• Functions can have an additional type parameter list introduced by the keyword type: func F(type T)(p T) { ... }.
• These type parameters can be used by the regular parameters and in the function body.
• Types can also have a type parameter list: type M(type T) []T.
• Each type parameter can have an optional type constraint: func F(type T Constraint)(p T) { ... }
• Type constraints are interface types.
• Interface types used as type constraints can have a list of predeclared types; only types whose underlying type is - one of those types can implement the interface.
• Using a generic function or type requires passing type arguments.
• Type inference permits omitting the type arguments in common cases.
• If a type parameter has a type constraint its type argument must implement the interface.
• Generic functions may only use operations permitted by the type constraint.

[cmdOptionKana]

盲猜因为初始方案是小括号，被说小括号太多。而小于号大于号本质上不是括号，可能会影响编译速度（或语法分析的复杂性），官方好像一开始就讨厌尖括号。所以折中一下就是中括号了。

[TypeError]

看起来还好，能和圆括号分清就行

[mind3x]

很好，迈出了走向 Scala 的第一步 [并没有]

[janxin]

因为不想用<>，因为不少额外有工作量，()有语法歧义

[Fitz]

唉, 什么时候改成方括号了, 记得 6 月份的时候不是圆括号吗

[so1n]

好像跟 python 不用<>的理由一样

[Fitz]

6 月份的帖子还在呢 https://v2ex.com/t/682238#r_9129287

[viktor123]

@Fitz thx bro.

[aloxaf]

看着比小括号舒服多了……

[allenhu]

恕我一眼看不懂

[iyear]

比尖尖的舒服多了。。。

[zhuangzhuang1988]

Scala 也是[]
<> 是留给 xml 用的

[tolerance]

等正式发布再说

[someonedeng]

其实看起来还不错

[yrj]

我记得上一稿方案是小括号，还是中括号舒服

[sunxiansong]

https://groups.google.com/forum/#!topic/golang-nuts/7t-Q2vt60J8%5B1-25%5D

https://www.reddit.com/r/golang/comments/hrce8e/go_generics_will_use_square_brackets_not/

[fengjianxinghun]

欢迎，[]()()() 比 ()()()()至少强了一分钱。

[lithbitren]

比小括号要更好

[fengjianxinghun]

```go

package main

import (
"fmt"
)


// The playground now supports parentheses or square brackets (only one at
// a time) for generic type and function declarations and instantiations.
// By default, parentheses are expected. To switch to square brackets,
// the first generic declaration in the source must use square brackets.


type primitive interface {
type string, int, uint, float32
}

func Print[type T primitive](s []T) {
for _, v := range s {
fmt.Print(v)
}
fmt.Print("\n")
}

func main() {
Print([]string{"Hello, ", "playground"})
Print([]int{1,2,3,4,5})
Print([]float32{1.0})
}


```

[Mohanson]

Golang 语法树解析的复杂度是 LR(1), 得益于其 Token 的 parser 是 context free 的. 按照 Go 的性格来说, 它不可能使用 <> , 因为一旦加上这个符号就会出现歧义, 要联系上下文去"猜"这个 Token 的含义, 复杂度会变成 LR(无穷). 括号内的数字和上下文的大小成正比.

编译速度在 Golang 看来是很重要的.

[fengjianxinghun]

@Mohanson 这点前端 parse 的开销基本微乎其微。

[Sasasu]

LR(1) 并不是复杂度