[Haskell-cafe] A Question of Restriction

Wouter Swierstra wss at cs.nott.ac.uk
Mon Jul 27 05:37:10 EDT 2009

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:


There are lots of ways to tackle this problem in Haskell - just google  
"Expression Problem Haskell". My (completely biased) personal  
favourite is:


Hope this helps,


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