问题描述
代数/2.1.1.2/doc/html 显示了种类繁多的类型类.
The documentation for algebra/2.1.1.2/doc/html shows a colossal number of type classes.
我如何声明所讨论的结构必须配备可交换的关联操作和单位/身份元素，但没有其他条件(逆，分布等)?
How do I declare that a structure in question must be equipped with a commutative associative operation and a unit/identity element, but without anything else (inverses, distributivity etc)?
我在想
reduce :: Monoid m => (a -> m) -> [a] -> m
但是Data.Monoid的实例不应该是可交换的，我希望函数的用户可以通过查看类型来了解他们需要函数的交换性.
but instances of Data.Monoid are not supposed to be commutative and I want users of my function to see that they need commutativity for the function to work by looking at the type.
推荐答案
(Abelian m, Monoidal m)
Monoidal似乎比您想要的要多得多，但这完全基于Natural是Semiring.
It might seem that Monoidal is much more than you want, but it is all based on Natural being a Semiring.
这篇关于来自Hackage的'代数'包的可交换monoid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！