From: Robert Klemme <shortcutter@...>
Date: 2007-07-19T21:30:35+09:00
Subject: Re: identify and extract positions from a string - how to?

2007/7/19, F. Senault <fred@lacave.net>:
> Le 19 juillet � 13:16, Marc Hoeppner a �crit :
>
> > and uses it in the extraction method
> >
> > file.readlines each do |l|
> >   puts string[l]
> > end
>
> The others solutions in the thread are the ones to use, but I feel the
> need to suggest the very dirty / insecure / bad one :
>
> File(filepath).readlines.each do |l|
>   puts string[eval(l)]
> end
>
> Don't try this at home, etc...  :)
>
> (But, in a controlled environment, it may be useful since it allows for
> all the variations that can be evaluated in one line of ruby code...)

A safer variant:

file.each do |line|
  if /^(\d+)\.\.(\d+)$/ =~ line
    puts string[ $1.to_i .. $2.to_i ]
  end
end

Note, that file.each is more efficient than file.readlines.each
because it does not need to read the whole file into memory.

Kind regards

robert