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This code is not sufficiently generic...huh...is it ?
f#

Hi everyone,

I'm trying to create a generic matrix structure that allow to work with any type of number (float, int,... but also custom types that implement +, -, *,... get_Zero, get_One,...)

[<StructAttribute>]
type Matrix< ^T > =
val Columns: array<array< ^T>>
new(x: int, y: int) = { Columns = Array.init x (fun _ -> Array.create y LanguagePrimitives.GenericZero< ^T>)}

In the constructor I filled the array with the generic 0 but it seems to be a problem for the compiler. I get this error message:

This code is not sufficiently generic. The type variable ^T when ^T : (static member get_Zero : -> ^T) could not be generalized because it would escape its scope.

I just discovered statically resolved type so at the moment I'm clueless.

Thanks for your help
E.

.

Only inline functions can use ^T. You can't use it as a generic class/struct type parameter.

By on 11/28/2010 9:01 PM ()

Only inline functions can use ^T. You can't use it as a generic class/struct type parameter.

Actually, this isn't quite true:

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type TyWithZero< ^T when ^T : (static member Zero : ^T)>() =
  member inline x.ZeroElement : ^T = LanguagePrimitives.GenericZero


let z = TyWithZero<int>().ZeroElement
let oops = TyWithZero<string>()  // won't compile; string has no static Zero member

However, since it's impossible to mark a constructor as inline the original code can't easily be made to work.

By on 11/29/2010 9:16 AM ()

Thank you for your answer.
Just to be sure...it's not possible to create a generic class/struct that would use arithmetic on the associated type (float, int, custom type,...) ?

By on 11/29/2010 3:46 AM ()

I'm working on it. By now you can use not very beautiful library. See a thread in General Discussion about type classes.
Library can be found here.

By on 11/29/2010 11:00 AM ()

Thank you :)

By on 1/11/2011 3:12 AM ()

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