haskell - 这个语法在 Haskell 中是什么意思 : _|_ or (_|_)

Question

我一直在许多受人尊敬的文档中看到这个相当令人尴尬的事情:_|_ 或 (_|_)
找不到它的定义(Google 不能很好地处理符号)。那到底是什么呢？

Answer 1

来自 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 '_|_'.

也来自 reserve keywords in Haskell 。

检查 wiki 中的 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.

给出了更多描述 here :-