From: "David A. Black" <dblack@...>
Date: 2004-12-01T10:14:40+09:00
Subject: Re: singleton methods : when are they not permitted?

Hi --

On Wed, 1 Dec 2004, Francis Hwang wrote:

> 
> On Nov 30, 2004, at 6:12 PM, Florian Gross wrote:
> > It also seems not to be possible to directly add methods to literals 
> > like this: (Not sure why -- maybe Ruby optimizes literals?)
> >
> > irb(main):014:0> def ("x").foo; end
> > SyntaxError: compile error
> > (irb):14: can't define singleton method for literals
> >
> > However this can be worked around trivially by using an expression 
> > instead:
> >
> > irb(main):015:0> def (("x")).foo; end
> > => nil
> 
> Errrr. So what's the difference between
> 
> def ("x").foo; end
> 
> and
> 
> def (("x")).foo; end
> 
> Why do the extra parens make the parser treat it differently? My head 
> hurts.

I think the difference is that (("x")) causes the expression inside
the inner parens to be evaluated first, so by the time it's seen by
def, it isn't a literal but the result of an evaluated expression.  So
def treats it as if it were seeing:

  a = "x"
  def (a).foo ...

At least that's my reading of it.


David

-- 
David A. Black
dblack@wobblini.net