Re: Type safety, C++ and code generation

[Georg Bauhaus <bauhaus@futureapps.de>]

Maciej Sobczak wrote:

> type ranged_type<int, 0, 250> Speed;
> Speed s1, s2, s3; // with some values
> s1 = s2 + s3; // OK
> s1 = s2 * s3; // not OK
> 
> The addition is fine, but the multiplication should not be provided,
> because speed multiplied by speed is not a speed. Can you extend your
> class so that the compiler will refuse to compile the second operation
> above?
> (Ada, anyone? :) )

Just so it is visible:


procedure useop is

   s1, s2, s3: SPEED;  -- with some values

begin
   s3 := s1 * s2;
end useop;

     8.    s3 := s1 * s2;
                    |
        >>> cannot call abstract subprogram "*"

where

package Op is

   type SPEED is range 0 .. 250;

   function "*"(a, b: SPEED) return SPEED is abstract;

end Op;