RE: [Haskell-cafe] Yet another stupid question about numeric conversion
On Tue, 21 Aug 2007, Peter Verswyvelen wrote: Yes indeed, I realized that. I oversimplified my question. I'm basically trying to model 4D CG/HLSL operations (pixel/vertex shaders) in Haskell. I tried realToFrac, but that did not work. Then I tried splitting the instances into Fractional and Integral, but I kept getting errors. Maybe because I also made the Vector datatype an instance of Num, Fractional, etc, which was needed to model the CG/HLSL piecewise operations (so multiplication of two vectors is done piecewise by default in the CG model; one has special dot, cross, and mul operations for performing the other operations). It would be nice if one could have a full predicate in the constraints section of a type class, like class ((Num a) not (Vector4D a)) = ... But I guess this indicates bad design? Is still don't see why you need it. I have the feeling that you abuse Num and Fractional classes just for re-use of symbols like (*) and (/) in an arbitrary way. Better don't do that. Type classes are for writing generic functions. Define new infix operators where necessary. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Yet another stupid question about numeric conversion
How can you hope to convert an arbitrary Num to a Float? Num contains things like complex numbers that don't have any reasonable translation to a Float. But anyway, realToFrac is a good conversion function. -- Lennart On 8/21/07, Peter Verswyvelen [EMAIL PROTECTED] wrote: Does a general approach exist to convert any non-constant (Num a) to a Float? Not using type annotation of course. Now I wrote a Convert class that has a toFloat function which I instantiate for all different numeric types, but as all these toFloat/toInt functions disappeared a long time ago from Haskell, it feels like a bad idea to reintroduce them locally in my code... Thanks (again!) Peter Verswyvelen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Yet another stupid question about numeric conversion
On Tue, 21 Aug 2007 18:53:43 +0200, Peter Verswyvelen [EMAIL PROTECTED] wrote: Does a general approach exist to convert any non-constant (Num a) to a Float? Not using type annotation of course. Instances of class Integral (Int and Integer) can be converted with fromIntegral. -- Met vriendelijke groet, Henk-Jan van Tuyl -- http://functor.bamikanarie.com http://Van.Tuyl.eu/ -- ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] Yet another stupid question about numeric conversion
Yes indeed, I realized that. I oversimplified my question. I'm basically trying to model 4D CG/HLSL operations (pixel/vertex shaders) in Haskell. I tried realToFrac, but that did not work. Then I tried splitting the instances into Fractional and Integral, but I kept getting errors. Maybe because I also made the Vector datatype an instance of Num, Fractional, etc, which was needed to model the CG/HLSL piecewise operations (so multiplication of two vectors is done piecewise by default in the CG model; one has special dot, cross, and mul operations for performing the other operations). Anyway, although I got something working when I enabled many GHC extensions, I dropped it for now. I notice that a lot of Haskell code uses type annotations (e.g. in HOpenGL), so I guess that's the price one has to pay. It would be nice if one could have a full predicate in the constraints section of a type class, like class ((Num a) not (Vector4D a)) = ... But I guess this indicates bad design? Thanks, Peter [EMAIL PROTECTED] wrote: How can you hope to convert an arbitrary Num to a Float? Num contains things like complex numbers that don't have any reasonable translation to a Float. But anyway, realToFrac is a good conversion function. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
