From: Justin Johnson <justinj@...>
Date: 2002-09-25T19:02:37+09:00
Subject: Re: adding overload to ruby


IMHO, I think that having dispatch like this would be cool.  But...

Issues:

1. It would have to be optional.  Each parameter could be either a var (as
it is now) or a class and var pair to specify specialization.

2. Making it efficient could be difficult.  It could potentially affect the
speed of all method lookups because a method call would have to get the
types of the arguments and try and find a matching method.  If it can't find
one it would presumably use the totally generic case.

    Example:

    def a_method( a, b, c )        #generic case
    ...
    end

    def a_method( String a, Fixnum b, Fixnum c )    #specialized case
    ...
    end

    a_method( "hello", 10, 20 )    #calls specialized case above

    a_method( 10, "hello", "there" )    #can't find specialized for
(Fixnum,String,String) so defaults to generic.

3. Bignum and Fixnum.  Conversion between these are automatic.  How does
this affect specialization?

    Example:

    def a_method( Fixnum a )
    ...
    end

    def a_method( Bignum a )
    ...
    end

    a_method( 1000 )            #calls Fixnum a_method
    a_method( 100000000000000000000000000 )        #calls Bignum a_method

    Is this desirable?  Probably not.


--
Justin Johnson

"Bulat Ziganshin" <bulatz@integ.ru> wrote in message
news:67179315231.20020924111057@integ.ru...
> Hello all and especially Matz,
>
> there is permanent discussion about adding overload facility to ruby
> and spirit of language. i want to add another cent to this :)
>
> 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
>
>