[Haskell-cafe] Re: Equations for `foo' have different numbers of arguments
Manlio Perillo manlio_peri...@libero.it 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. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Equations for `foo' have different numbers of arguments
Achim Schneider wrote: The other might be implementation issues: it makes pattern match rules more complex. But only marginally, right? f A B = biz f B = bar f = bam could be trivially rewritten to: f A B = biz f B y = bar y f x y = bam x y Martijn. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Equations for `foo' have different numbers of arguments
Yes, but this seems to have terrifying implications... On Tue, Mar 24, 2009 at 11:25 AM, Martijn van Steenbergen mart...@van.steenbergen.nl wrote: Achim Schneider wrote: The other might be implementation issues: it makes pattern match rules more complex. But only marginally, right? f A B = biz f B = bar f = bam could be trivially rewritten to: f A B = biz f B y = bar y f x y = bam x y Martijn. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- /jve ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Equations for `foo' have different numbers of arguments
Martijn van Steenbergen mart...@van.steenbergen.nl wrote: f x y = bam x y This would introduce another matching of x on the outside of bam, and I don't know if this works without significantly messing with e.g. strictness. -- (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. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
