On Sun, Jan 3, 2010 at 11:30 PM, Felipe Lessa
On Sun, Jan 03, 2010 at 10:38:28PM +0100, Francesco Guerrieri wrote:
But doesn't ever happen that poor liftM be confused? and do poor haskell programmers never feel the need to explicitly state to which monad they "wish to lift" ?
If by "explicitly state to which monad" you mean specializing liftM or fmap, then the answer is no. It is not uncommon to see
fmap (fmap function)
being used to map two layers of structures. If by stating you mean giving a type signature, then yes, it is a good practice to give type signatures to all top-level definitions.
I was thinking to type signatures :-) By the way, you all refer to top-level definition. But in the map show . map read example, what I see at the top-level is [String] -> [String]. This probably means that my understanding of what is a top-level definition is faulty...
The compiler never gets "confused". The only thing that may happen is having more than one possible type that fulfills your needs. The classical example is Num overloading:
This is a very clear example, thanks! Francesco