From: Kevin Brown <blargity@...>
Date: 2005-12-08T04:22:33+09:00
Subject: Re: increasing counter whithin loop?

On Wednesday 07 December 2005 11:51, mental@rydia.net wrote:
> Quoting Patrick Gundlach <clr9.10.randomuser@spamgourmet.com>:
> > This is why I thought
> >
> > for i in sequence
> >   if sequence[i]=='b' and sequence[i+1]=='b'
> >    output 'double b'
> >    # increase i, so that the second 'b' won't be seen by the
> > for-loop
> >    # but ruby won't let me!?
> >    # i += 1 does nothing
> >   else
> >    output sequence[i]
> >   end
> > end
> >
> > would work, but I can't change the i in the for-loop. This is a
> > pity!
>
> It's probably helpful to realize that Ruby has no for-loop in the
> traditional sense.  The above is equivalent to:
>
>  sequence.each do |i|
>    if sequence[i]=='b' and sequence[i+1]=='b'
>     output 'double b'
>     # increase i, so that the second 'b' won't be seen by the
>  for-loop
>     # but ruby won't let me!?
>     # i += 1 does nothing
>    else
>     output sequence[i]
>    end
>  end
>
> Written this way, it's probably more obvious why incrementing i
> doesn't do what you had expected.
>
> -mental

If you're really tied to the traditional for loop, you can use a while loop 
and do the increment yourself at the end of the loop, but usually you find a 
better way to do it in Ruby that doesn't involve going through the chars one 
at a time, and that's why we rarely use the for construct.