Re: [Haskell-cafe] Suggestions for improvement

On 10/3/10 1:45 PM, Dominique Devriese wrote:

Additionally, you can't combine the functions (blowup . allButLast) and lastToTheLength into a function that returns a pair like you seem to attempt. You need a function like the following for that:

comma :: (a -> b) -> (a -> c) -> a -> (b,c) comma f g x = (f x, g x)

Then you could say:

blowup = (uncurry (++)) . comma (blowup . allButLast) lastToTheLength

It is worth noting that such a function already exists in the standard libraries; it is the &&& operator in Control.Arrow: blowup = uncurry (++) . (blowup . allButLast &&& lastToTheLength) Cheers, Greg