#!/usr/bin/env ruby
# This code comes from http://ruby-it.org/pages/Espressioni+Regolari+Ripetizioni
# Check the page for copyright notice and explanations



 >> rgx= /sa*s/
 => /sa*s/
 >> 'sas' =~ rgx
 => 0
 >> 'saas' =~ rgx
 => 0
 >> 'saaas' =~ rgx
 => 0
 >> 'ss' =~ rgx
 => 0

 >> rgx= /s./
 => /s./
 >> 'ss' =~ rgx
 => 0
 >> 's ' =~ rgx
 => 0
 >> 's#' =~ rgx
 => 0 
 >> 's' =~ rgx
 => nil

 >> rgx= /s.*o/
 => /s.*o/
 >> "sesso" =~ rgx
 => 0
 >> "sasso" =~ rgx
 => 0
 >> "sono io" =~ rgx
 => 0
 >> "s o" =~ rgx
 => 0
 >> "s " =~ rgx
 => nil

 >> rgx= /s.?o/ # una s, una ripetizone o zero di un carattere qualsiasi e una o
 => /s.?o/
 >> 'sio'=~ rgx
 => 0
 >> 'so'=~ rgx
 => 0
 >> 'saao'=~ rgx
 => nil

 <carattere>?<carattere>*

 <carattere>+

 >> rgx= /s.+o/ # una s, uno o piu' caratteri qualsiasi e una o
 => /s.+o/
 >> 'so'=~ rgx
 => nil
 >> 'sao'=~ rgx
 => 0
 >> 'sono io'=~ rgx
 => 0
 >> 'sono io'=~ rgx

 >> rgx= /a{1,2}/
 => /a{1,2}/
 >> 'ciao' =~ rgx
 => 2
 >> 'ciaao' =~ rgx
 => 2
 >> 'cio' =~ rgx
 => nil

 >> rgx= /a{2}/
 => /a{2}/
 >> 'ciaao' =~ rgx
 => 2
 >> 'ciao' =~ rgx
 => nil