From: Alder Green <alder.green@...>
Date: 2006-05-26T17:12:22+09:00
Subject: Re: Method '!='

On 5/26/06, Dave Burt <dave@burt.id.au> wrote:
> On 5/26/06, Alder Green wrote:
> > Trying to define a method != doesn't wfm, even with define_method:
> >
> > irb(main):013:0> class Object; define_method(:!=) {|arg| self != arg }; end
> > class Object; define_method(:!=) {|arg| self != arg }; end
> >
> > SyntaxError: compile error
> > (irb):13: parse error, unexpected tNEQ, expecting tSTRING_CONTENT or
> > tSTRING_DBEG or tSTRING_DVAR or tSTRING_END
> > class Object; define_method(:!=) {|arg| self != arg }; end
> >                                ^
>
> No, just that symbol syntax. :!= is not a valid symbol. "!=" will work
> just fine, though.
>
> irb(main):001:0> class << self
> irb(main):002:1> define_method("!=") {}
> irb(main):003:1> end
> => #<Proc:0x00000000@(irb):3>
>
> Cheers,
> Dave

Yup, good tip. However, the relations between the operator syntax and
the method calls reveals itself to be more mysterious than I thought:

class Foo
  define_method('!=') { 'Foo#!= was called' }
  define_method('==') { 'Foo#== was called' }
end

irb(main):003:0> foo = Foo.new
#<Foo:0x2c88e28>

irb(main):004:0> foo != 1
false   # looks like 'foo != arg' isn't simply syntactic sugar for !foo.==(arg)

irb(main):005:0> foo.==
"Foo#== was called"

irb(main):008:0> foo.send '!='
"Foo#!= was called"      # And send seems to be the only way to call !=

But as far as Victor is concerned, as long as #send is used, those
methods would work as expected.

-- 
-Alder