Re: [Haskell-cafe] A Question of Restriction

Hi Brian, If I understand you correctly, you've run into the "Expression Problem". Phil Wadler posed the problem in a widely-cited e-mail, formulating it much more clearly than I ever could: http://homepages.inf.ed.ac.uk/wadler/papers/expression/expression.txt There are lots of ways to tackle this problem in Haskell - just google "Expression Problem Haskell". My (completely biased) personal favourite is: http://www.cse.chalmers.se/~wouter/Publications/DataTypesALaCarte.pdf Hope this helps, Wouter