From: "Choi, Junegunn" <jg@...>
Date: 2009-02-11T20:53:17+09:00
Subject: Re: Method to get string combinations

Hi, this is my code just for unfolding braces in a string. It also
tries to handle nested braces like Dir.glob. Seems working fine.

def unfold(string)
    def recursion(input, list)
        num_groups = 0
        input.scan(/\{([^{}]*?)\}/) do | group |
            prefix, suffix = $`, $'
            num_groups += 1
            tokens = group[0].split(/[,|]/)
            tokens = [''] if tokens.empty?
            tokens.each do | token |
                recursion(prefix + token + suffix, list)
            end
            break
        end
        list << input if num_groups == 0
    end
    list = []
    recursion(string, list)
    list.uniq
end

puts unfold("This {is|was} a {good|nice} day")

# A more complex one
puts unfold('Who is {th{is,at},she,he,it} {?,!}{}')