这个语法在Haskell中意味着什么：_ | _或（_ | _） [英] What does this syntax mean in Haskell: _|_ or (_|_)

问题描述

在许多受尊敬的文件中，我总是看到这个令人尴尬的事情： _ | _ 或（_ | _）

无法找到它的定义（Google对符号不适用）。那么究竟是什么呢？

here ： -

底部

底部的数学符号是'⊥'。这是Unicode字符
22A5十六进制= 8869十进制。在HTML中也可用'⊥'和
LaTeX作为'\ bot'（在数学模式下）。在纯ASCII的情况下，它通常被写为
作为非常难看的字符序列'_ | _'。

同样来自在Haskell中保留关键字。

请访问wiki以了解底部和部分功能
$ b

要定义部分函数，​​我们引入一个特殊值⊥，命名为
bottom，并且通常写成 | 以打字机的字体。我们说⊥是
完全未定义的值或函数。每一个基本的数据类型
像Integer或（）都包含一个⊥，除了它们通常的元素外。

href =http://blog.ezyang.com/2010/12/hussling-haskell-types-into-hasse-diagrams/ =noreferrer> here ： -

I keep seeing this rather embarrassing thing in many respected documents: _|_ or (_|_)

Cannot find a definition of it (Google doesn't work well with symbols). So what is it anyway?

解决方案

From here:-

Bottom

The mathematical symbol for bottom is '⊥'. That's Unicode character 22A5 hex = 8869 decimal. Also available in HTML as '⊥' and in LaTeX as '\bot' (within math mode). In plain ASCII, it's often written as the extremely ugly character sequence '_|_'.

Also from the reserve keywords in Haskell.

Check the wiki for Bottom and Partial Functions

To define partial functions, we introduce a special value ⊥, named bottom and commonly written | in typewriter font. We say that ⊥ is the completely "undefined" value or function. Every basic data type like Integer or () contains one ⊥ besides their usual elements.

More description is given here:-

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