[Haskell-cafe] How to write (FxF' . delta) AxB --> F A
Johan Glimming
glimming at kth.se
Mon Feb 7 15:30:22 EST 2005
Hello
This might be a trivial question, but I wonder if anybody knows how to
write a function
proj :: (Functor f, Functor f') =>
(f:*:f') (a,b) -> f a
where
data a:*:b o = Pair (a o) (b o)
I think I really want to project out a component of F (AxB) x F' (AxB).
However, this seems harder in Haskell than in category theory, but I am
not 100% sure.
Best Wishes,
Johan Glimming
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