Your first search
The Haskell API Search can search for either names, or types. For example, to find the standard
map :: (a -> b) -> [a] -> [b] function you could search for:
map (a -> b) -> [a] -> [b] (a -> a) -> [a] -> [a] (Int -> Bool) -> [Int] -> [Bool] [a] -> (a -> b) -> [b]
The results in order
The API search tries to find as many results as it can. For name searches, an exact substring of the name must match (so 'ap' would match 'map'). For type searches, anything that will unify is returned. In addition, arguments can be reordered - i.e.
[a] -> (a -> b) -> [b] will still match
Because lots of results may be returned, they are sorted in order of usefulness. Those which are closer to the asked for information are given higher priority, those which are further are given lower priority.
After you have found the function, you can click on it to view details. The information comes from GHC's documentation.