functor
· One min read
什么是范畴(category)?
范畴就是两个对象+一个映射关系组成的东西
什么是函子(functor)?
函子就是两个范畴加上这两个范畴的映射关系而组成
也就是说函子就是范畴+两个范畴的映射
hom函子是什么(hom functor)? // todo
Set
Set is the category with
objects: all sets.
arrows: given sets X, Y , every (total) set-function f : X -> Y is an
arrow.
type and function
类型是范畴里面的对象 函数是其中的箭头, 这样是对的吗? 好像不太对,那就应该是错的,但是他们隐隐中有关系,但是不像是是范畴.
相关阅读
- https://www.johndcook.com/blog/2018/08/06/hom-functors/
- https://math.stackexchange.com/questions/94007/proof-of-yoneda-lemma
- https://www.emathzone.com/tutorials/group-theory/properties-of-isomorphism.html
- https://www.math3ma.com/blog/the-yoneda-lemma
- https://www.cnblogs.com/catch/p/3973104.html
- https://www.haskell.org/tutorial/haskell-98-tutorial.pdf
- https://bartoszmilewski.com/2013/05/15/understanding-yoneda/
- https://bartoszmilewski.com/2014/11/24/types-and-functions/