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"DR" == Dennis Raddle writes:

DR> Also I think "data a la carte" might be applicable to me, but again I DR> would need some kind of tutorial. Wouter Swiestra's original paper is an excellent resource for understanding both the problem and the solution: http://www.cs.ru.nl/~W.Swierstra/Publications/DataTypesALaCarte.pdf If you're looking for something even simpler than that, might I suggest: http://blog.sumtypeofway.com/an-introduction-to-recursion-schemes/ -- John Wiegley GPG fingerprint = 4710 CF98 AF9B 327B B80F http://newartisans.com 60E1 46C4 BD1A 7AC1 4BA2