[Haskell-cafe] Name that function =)
Louis J Scoras
louis.j.scoras at gmail.com
Tue Dec 12 11:29:11 EST 2006
I'm new to the list, so I just wanted to say hi and -- of course --
ask a quick question:
I have some IO actions that I want to map over a list of pairs --
these are just directory names and their down-cased versions. It
wasn't difficult to actually get the right behavior by just doing mapM
-- putDirs just outputs something like "mv fst snd"
mapM_ putDirs pairs
mapM_ (uncurry renameFile) pairs
This bothered me though, because I suspected that this could be done
in one pass. Naively I proceeded to this.
mapM_ (putDirs >> (uncurry renameFile)) pairs
Which didn't work. I thought about it a little more before realizing
that putDirs wouldn't get any parameters this way: I needed some way
to distribute the pair over both operations. Here's the higher-order
function I needed:
foo h f g i = h (f i) (g i)
which could then be curried and we get:
mapM_ (foo (>>) putDirs $ uncurry renameFile) pairs
Works great. So my question: is there a established name for foo?
What about foo partially applied to (>>)? This was a fun exercise,
but I'd like to use the standard implementations if they exist.
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