Luke Palmer wrote:
So I suppose that's my proposal. Allow, even encourage, overloading
of =:=, but only for value types. I've been thinking that we ought to
provide a standard role for making something a value type. Maybe it
would require definition of =:=.
I would like to propose something slightly different:
1) Let =:= be non-overloadable purely macro/grammar based
--- same could be applied to ::= and := I think
2) the implementation of =:= then checks type homogenity
as a precondition and calls the type specific EQUAL
submethod or some such
The rational is that type homogenity is a necessary condition
for identity and thus allows to return false when violated.
The EQUAL class/type submethod could be used as the default for
the == and eq operators as long as subtype homogenity for both
sides holds. Well, or the operator name is a parameter to the
parametric role:
role Identity[ &eq_op:( ::?CLASS, ::?CLASS: --> bit ) = $::CLASS::EQUAL ]
does Identity[ ::?CLASS ] # F-bounded
{
...
}
which is implicitly forced into every class definition by virtue of
role Any does Identity;
In particular we have:
class Num does Identity[ &infix:{'=='} ] {...}
class Str does Identity[ &infix:{'eq'} ] {...}
To what exteent in canbe auto-generated with dispatching to
the respective methods of all elements defined into the class'
value environment, I can't say.
--
TSa (Thomas Sandlaß)
