From: rsc@swtch.com   
      
   > Nonetheless, it's an interesting exercise.  Will probably use it in a   
   > data structures course some time in the future.  If you want to   
   > implement the "obvious" recursive solution and still generate every   
   > possible string, you effectively need coroutines to do alternation.   
      
   Or lazy evaluation (same thing).  Doug McIlroy's functional pearl   
   "Enumerating the strings of regular languages" in JFP (preprint at   
   http://www.cs.dartmouth.edu/~doug/nfa.ps.gz) gives elegant Haskell   
   code to generate texts both directly from the regular expression (the   
   grammar route) and from the equivalent automaton.   
      
   Russ   
      
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