Add reference to related work by McIlroy?

[FranklinChen]

Cool tool! It might be educational to include in the README mention of McIlroy's 2004 Functional Pearl "Enumerating the strings of regular languages" http://www.cs.dartmouth.edu/~doug/nfa.ps.gz

[nmattia]

Thanks, I'll have a look when I get the time. To be honest I haven't looked at the research before getting started, though better late than never.

[nmattia]

Thanks for a good read! I wish I had known about it when I first implemented
stutter.

A few thoughts:

• I realize that stutter's operators don't have the same priority as typical
  regex s; for instance, running the paper's regex examples through stutter
  yields different output sets (the elements are different, not just the
  ordering). I might need to look into that.

• It looks like stutter could be reimplemented easily using the first method
  described in the paper. I'll first try to write a conduit-based library for
  the length-ordered list operations. If that works, it should be possible to
  preserve the constant memory behavior.

• Currently stutter supports more operators than those defined by the Rexp
  type (stutter uses regex-like expressions). However it should still be
  possible to write a conduit-based LOL library in tagless final style and
  extend the types in stutter. I planned to go in that direction anyway (finally tagless producer #8)
  so might as well.

I'll reach out to Prof. McIlroy to see if he's fine with me putting up a
conduit-based library of the set operations method on hackage. @FranklinChen your thoughts on this are very welcome.

[FranklinChen]

I'm too busy at the moment to look into a comparison and consolidation of the techniques, but I'm glad you found the reference useful and will watch for developments :-).