(f a b) still doesn't make a lot of sense, I assume (a -> b) was meant in that argument type. On Mar 3, 2016 21:13, "Rein Henrichs" wrote:

Ben, I just assumed that g was a typo for f.

On Thu, Mar 3, 2016 at 10:10 AM Ben Rogalski wrote:

...

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

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