Re: Dylan implementation question

[address@hidden (Peter S. Housel)]

At Tue, 05 Mar 2002 01:30:02 -0500, Steve Schafer wrote:
> Thanks to all for the hint--it makes sense now. I guess the only
> additional complication is that the presence of specializers attached
> to keyword parameters might require the use of several different
> "not-supplied" constants of different types.

That's not usually necessary.  You could just use a type-union:

define method foo(bar :: <bar>,
                  #key baz :: type-union(<baz>, singleton($not-supplied))
                     = $not-supplied);
  // ...
  if($baz ~== $not-supplied)
    // at this point the compiler knows baz must be of type <baz>
    // ...
  end if;
  // ...
end method;

-Peter-