Hi John,
I don't know if this is useful for you, but these are instances of
Cofunctor's comap. For example if we use TypeCompose package we have:
rebox f = unFlip . cofmap f . Flip
The rest are also Cofunctors. There are a few options. You can either
specify instances or use type combinators from category-extras or
TypeCompose packages. Basically (a -> a -> b) is curried composition
of diagonal Functor from Bifunctor (,) and Cofunctor (Flip (->) a)
etc.
It's interesting to know more about usage of the pattern for AST reduction.
Vitaliy
On Tue, Dec 8, 2009 at 9:37 PM, John Van Enk
Hi List, I've recently had a situation where I used the same pattern quite a bit while reducing and evaluating an AST. I quickly wrapped the operation in a package and stuck it on github. http://github.com/sw17ch/rebox/blob/master/src/Data/Rebox.hs I'm wondering two things: 1) Does any one recognize the pattern I'm using here as something with a different name? 2) Is this worth sticking on Hackage? It's trivial, but we have plenty of trivial concepts on Hackage (and it's not a bad thing). Any feedback would be great. /jve
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