3 Mar
2016
3 Mar
'16
2:13 p.m.
Ben, I just assumed that g was a typo for f.
On Thu, Mar 3, 2016 at 10:10 AM Ben Rogalski
I'm having trouble understanding this:
IIUC, one would describe fmap as "lifting" a function g into a functor f, in the sense of
Functor f => (g a b) -> g a -> g b
Is there an inverse concept (? co-lift ?) that describes
Functor f => (g a -> g b) -> a -> b
It seems like these are type declarations for functions, with class constraints that say f must be a Functor, but then f doesn't appear anywhere else in the declaration. Why is this?
Thanks, -Ben _______________________________________________ Beginners mailing list Beginners@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners