[Haskell-cafe] Re: Equations for `foo' have different numbers of arguments

Manlio Perillo wrote:

Hi.

There is a limitation, in Haskell, that I'm not sure to understand. Here is an example:

module Main where

divide :: Float -> Float -> Float divide _ 0 = error "division by 0" divide = (/)

main = do print $ divide 1.0 0.0 print $ divide 4.0 2.0

With GHC I get: Equations for `divide' have different numbers of arguments

With HUGS: Equations give different arities for "divide"

However the two equations really have the same number of arguments.

What's the problem?

Equations not being what you think they are. They aren't "the symbol 'divide' equals that function" but "lhs of '=', '=', and rhs of '='. The problem is mostly syntactical, in the sense that most occurrences of definitions with a different number of arguments are plain typos. The other might be implementation issues: it makes pattern match rules more complex. -- (c) this sig last receiving data processing entity. Inspect headers for copyright history. All rights reserved. Copying, hiring, renting, performance and/or quoting of this signature prohibited.