Haskell“Dot Hack” [英] Haskell "Dot Hack"

问题描述

在 Sudoku解决方案的Wiki页面中，一个解决方案声称使用Dot黑客。链接的Github页面不再可用，我也找不到任何有关它的地方。

In the Wiki page for Sudoku solutions, one solution claims to use the "Dot Hack". The linked Github page is no more available and I couldn't find anything about it elewhere.

这是关于什么的？它有什么作用？如何？

What is this about? What does it do? How?

推荐答案

我猜他是指以下行：

I guess he's referring to the following line:

import Prelude hiding ((.))

正常（。）运算符用于功能组合。相反，使用另一个名称相同的运算符，可能从实用程序模块 T.T 中导入。此运算符的行为与OOP语言相似：

which disables the normal (.) operator for functional composition. Instead, another operator with the same name is used, probably imported from the utility module T.T. This operator behaves like in OOP languages:

pretty_output solution = solution.elems.map(show).in_group_of(9)
    .map(unwords).unlines

哪些（我认为）通常看起来像

which (I think) would normally look like

pretty_output solution = (unlines . map unwords . in_group_of 9 . map show . elems) solution

该操作符与 |> 运算符：

That operator works the same like the |> operator in F#:

(|>) :: a -> (a -> b) -> b
x |> f = f x

它用于通过函数（更具可读性和更好的功能风格，imo）：

which is used to pipe a value through functions (and is more readable and better functional style, imo):

pretty_output solution = solution |> elems |> map show |> in_group_of 9 |> map unwords |> unlines

（|>）也是与 flip（$）。

相同。编辑：这个hacked操作符已经存在于Haskell中。从 Control.Category ：

This "hacked" operator already exists in Haskell, somehow. The same composition behavior can be achieved by the left-to-right composition operator from Control.Category:

g x = x |> (f1 >>> f2 >>> f3)

，但实际上只是 f>>> g = g。 f 。

这篇关于Haskell“Dot Hack”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！