[Haskell-cafe] Ratification for my understanding of functors

C K Kashyap ckkashyap at gmail.com
Sat Jan 8 11:23:24 CET 2011


Thanks to Luke Palmer's explanation. I got a better idea of functors.
I just want to ratify my understanding of what a functor is -
according to category theory, functors are arrows between categories
... these arrows map objets and arrows from one category into another.

So, would it be right to say that the list type constructor + the map
function form the functor? Saying "list is a functor then is a
convenient approximation right?

In this context, could someone please point me to some writeup on
co-variant/contravariant type constructors? Googling for it seems to
only give a lot of C++/Java/C# hits.


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