[Haskell-cafe] Re: Map list of functions over a single argument

apfelmus at quantentunnel.de apfelmus at quantentunnel.de
Tue Feb 20 12:08:01 EST 2007

Paul Moore wrote:
> I'm after a function, sort of equivalent to map, but rather than
> mapping a function over a list of arguments, I want to map a list of
> functions over the same argument. The signature would be [a -> b] -> a
> -> [b], but hoogle didn't come up with anything.
> It seems like an obvious analogue of map, so I'm pretty sure I'm
> missing something (otherwise, I'd just write it myself, and not bother
> :-))
> Can anyone point me in the right direction?

It's also known as

  sequence :: Monad m => [m b] -> m [b]

with m = (->) a

  sequence :: [a -> b] -> (a -> [b])

This is the fabulous MonadReader.


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