人们为什么使用_?作为标识符后缀? [英] Why do people use _? as an identifier suffix?

问题描述

我开始阅读Lift框架源代码，发现使用methodName_?之类的名称定义了很多方法，是否有约定_?具有某些特殊含义?

I start reading Lift framework source code, I find that there're so many methods are defined using a name like methodName_? , is there a convention that _? has some special meaning?

def empty_? : Boolean = {}

推荐答案

?表示这是一个谓词，一个返回Boolean的函数.此约定可以追溯到Lisp，其中?(方案)，p或-p(其他Lisps，用相似"字母模拟问号)也表示谓词.认为它是一个问题，对象是空的吗?"

The ? denotes that this is a predicate, a function returning Boolean. This convention goes back to Lisp, where ? (Scheme), p or -p (other Lisps, simulating the question mark with a "similar" letter) also denote predicates. Think of it as asking a question, "is the object empty?"

Scala仅允许使用_分隔混合的标识符名称(包含字母数字和标点符号).例如，

Scala will only allow mixed identifier names (containing alphanumerics and punctuation) if you separate them by _. E.g.,

scala> def iszero?(x : Int) = x == 0 
<console>:1: error: '=' expected but identifier found.
       def iszero?(x : Int) = x == 0
                 ^

不起作用，但是

scala> def iszero_?(x : Int) = x == 0          
iszero_$qmark: (x: Int)Boolean

确实.

这篇关于人们为什么使用_?作为标识符后缀?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！