From: James Edward Gray II <james@...>
Date: 2007-07-24T13:10:53+09:00
Subject: Re: finding positions in a string

On Jul 23, 2007, at 3:54 PM, bwv549 wrote:

> I have a long string and I need to know the starting position of all
> substrings matching a particular sequence.  Most importantly, it needs
> to be fast.  Secondly, it would be nice if it was somewhat concise.
>
> Here's the method:
>
> def substring_positions(substring, string)
> ## fast, concise method??
> end
>
> my_substring = 'this'
> my_string = 'this string this is a string this is it'
>
> substring_positions(my_substring, my_string)      # -> should return
> [0, 12, 29]

Another idea is to use String#index() with the optional second  
minimum index parameter which you keep incrementing.

James Edward Gray II