From: Justin Johnson <justinj@...>
Date: 2002-09-25T23:02:55+09:00
Subject: Re: adding overload to ruby


> not class, but any expression - we can use === to test

Of course. Cool.

> def a_method( Integer a)
> end
>
> def b_method( Numeric a)
> end

Yes, I thought of this.  This means however that the lookup needs to work
with class hierarchies:

    a_method( 10 )        # parameter is a Fixnum object

Lookup for a_method with a Fixnum find a match.  So the call has to navigate
the Fixnum hierarchy to try and find a match.  This gets slower/harder with
multiple arguments.

> no. if the method definition don't use type specifiers, this method is
> not overloaded. as with overload.rb

Ok, but how does the runtime know wether a method call is overloaded at the
point of call?  It doesn't.  It would have to work out the argument classes
and perform a lookup based on them.  For most method calls it wouldn't find
a specialized version and would have to call the generic method instead.

--
Justin Johnson

"Bulat Ziganshin" <bulatz@integ.ru> wrote in message
news:16124073525.20020925163403@integ.ru...
> Hello Justin,
>
> Wednesday, September 25, 2002, 2:02:37 PM, you wrote:
>
> JJ> 1. It would have to be optional.  Each parameter could be either a var
(as
> JJ> it is now) or a class and var pair to specify specialization.
>
> not class, but any expression - we can use === to test
>
> JJ> 2. Making it efficient could be difficult.  It could potentially
affect the
> JJ> speed of all method lookups because a method call would have to get
the
> JJ> types of the arguments and try and find a matching method.  If it
can't find
> JJ> one it would presumably use the totally generic case.
>
> no. if the method definition don't use type specifiers, this method is
> not overloaded. as with overload.rb
>
> JJ> 3. Bignum and Fixnum.  Conversion between these are automatic.  How
does
> JJ> this affect specialization?
>
> def a_method( Integer a)
> end
>
> def b_method( Numeric a)
> end
>
> >> now i can use overload library and write code such as:
> >>
> >> >   def do_overload(i, s, f)
> >> >   end
> >> >   overload(:do_overload, Fixnum, String, Float)
> >> >
> >> >   def do_overload(s, i, *a)
> >> >   end
> >> >   overload(:do_overload, String, Fixnum)
> >>
> >> all that i want - just the same (terrible, you are right) semantics
> >> with a bit more clear syntax and including this feature into ruby
> >> distribution:
> >>
> >> >   def do_overload(Fixnum i, String s, Float f)
> >> >   end
> >> >   def do_overload(String s, Fixnum i, *a)
> >> >   end
> >>
> >> although this don't correspond to dynamic spirit of language, in real
> >> world this adds lot of points to ease of use and even robustness of
> >> language
>
>
> --
> Best regards,
>  Bulat                            mailto:bulatz@integ.ru
>
>