From: Brian Candler <B.Candler@...>
Date: 2003-08-08T02:55:40+09:00
Subject: Re: Elegant solution for a loop-break problem

On Fri, Aug 08, 2003 at 01:46:20AM +0900, Rudolf Polzer wrote:
> he means, that in Perl you can do:
> 
>   use Data::Dumper;
>   @l = qw(one two three);
>   for my $elem(@l)
>   {
>     $elem = 'X' . uc $elem;
>   }
>   print Dumper \@l;
> 
> which yields
> 
>   $VAR1 = [
>             'XONE',
>             'XTWO',
>             'XTHREE'
>           ];

In Ruby:

    l = %w{one two three}
    l.each do |elem|
      elem.replace('X' + elem.upcase)
    end
    p l

In other words, you have to mutate the existing element; assigning to 'elem'
does not replace the element, it simply makes the local variable point
elsewhere.

There is some Bad Magic going on in the Perl version; somehow $elem is
aliasing an element of the array, it is not a normal variable at all.

> Of course, elem.upcase!() would solve the problem... but in this case,
> eventually the equivalent of Perl's map operator, Array#collect and
> Array#collect!, are more appropiate:
> 
>   l = %w{one two three}
>   l.collect!() do |elem|
>     'X' + elem.upcase()
>   end
>   p l

Except the question was about hashes, and hashes don't have collect! (which
is really an Array method)

Regards,

Brian.