From: Dave Oshel <dcoshel@...>
Date: 2003-05-26T10:37:15+09:00
Subject: Re: why is "does" missing from this sub!-stitution?

In article 
<Pine.LNX.4.44.0305240751280.28889-100000@candle.superlink.net>,
 dblack@superlink.net wrote:

> Hi --
> 
> On Sat, 24 May 2003, Dave Thomas wrote:
> 
> > dblack@superlink.net wrote:
> >
> > > I'm with you on the 'what', but I'm still curious about the 'why'.
> > > It's true that the replacement string gets parsed before sub is
> > > called.  But I think "abcdef" gets matched against the regex even
> > > before that parse happens.
> >
> >
> > But it doesn't. Think about it this way
> >
> >    def fred(a, b)
> >      $x = 1
> >      puts a
> >      puts b
> >    end
> >
> >    $x = 99
> >    fred(11, $x)
> >    fred(11, $x)
> >
> > #=>
> >    11
> >    99
> >    11
> >    1
> >
> > The parameters to a method are evaluated at the point of call: the
> > method can't affect the value of its parameters.
> 
> I'm hip to this part (see ruby-talk:70238 for proof :-)  It's the \1
> thing that I've managed to garble.  I've been thinking: if $1 hasn't
> been reassigned yet, then how can \1 mean anything?  But the answer, I
> now see, is: it means \1, which gets passed literally to the method,
> which *then* knows what to do with it.
> 

Ok, I sort of understand that.  But the corresponding Perl syntax seems 
more obvious, to my aching head.

Is there a Ruby gotchas page, somewhere on the web?

-- 
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