[Haskell-cafe] Parsec monad transformer with IO?

Andrew Coppin andrewcoppin at btinternet.com
Thu Mar 18 17:34:48 EDT 2010

Job Vranish wrote:
> Hoogle is a great tool for finding haskell functions:
> http://www.haskell.org/hoogle/
> You can punch in the type of a function you want and it will give you 
> a list of functions that might do what you need.
> Generalizing the types a bit usually helps. Searching for either  m a 
> -> n m a   or   IO a -> m a   would give you 'lift' and 'liftIO' as 
> one of the top results.

Is there a tool anywhere which can figure out how to construct a 
function with a specific type signature? Hoogle works if the thing you 
seek is a single function, but not so much if you need to throw several 
functions together.

(For example, the signature "x -> [x -> y] -> [y]" can be implemented by 
\ x -> map ($ x), but this is initially non-obvious.)

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