Re: Inferred type is not general enough

"Cagdas Ozgenc" <co19@cornell.edu> writes:

The following function generates a type error.

headColumnwise :: [a] -> a headColumnwise line = [ head line | line <- p ]

Surely, the parameter should be "p"?

ERROR ch6ex1.hs:14 - Inferred type is not general enough *** Expression : headColumnwise *** Expected type : [a] -> a *** Inferred type : [[a]] -> [a]

it compiles fine. Isn't [a]->a the most general type here?

If p is [a], then line (drawn from p) must be of type a. But you do "head line", which implies that line (and thus a) is a list. -kzm -- If I haven't seen further, it is by standing in the footprints of giants