From: mental@...
Date: 2005-12-08T02:51:42+09:00
Subject: Re: increasing counter whithin loop?

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