Re: Parametrically polymorphic operations (Was: Safe C++)

[Wes Groleau <wwgrol@sparc01.ftw.rsc.raytheon.com>]

Jacob Sparre Andersen wrote:
> safe types, I have certainly wanted something very similar
> to parametrically polymorphic functions. It would make it
> possible to have more extensive compile time checks, than
> what is possible with Ada as it is defined today.
> 
> An example:
> 
>    type Matrix (Left, Right : Positive) is private;
> 
>    function "*" (Left  : in Matrix;
>                  Right : in Matrix (Height => Left.Width))
>      return Matrix (Width  => Right.Width,
>                     Height => Left.Height);

Where are you going to put the result?

If the implementation is reasonable, constraint_error
will be raised when the constraints on the left side don't
the constraints on the result.

And if the constraints are static on both, many compilers
will detect it at compile time.

-- 
Wes Groleau
http://freepages.rootsweb.com/~wgroleau