[Haskell-cafe] typeclass constraint question

Jeff Polakow jeff.polakow at db.com
Thu Dec 14 09:54:01 EST 2006


I'm trying to understand what happens when a typeclass constraint with an 
uninstantiated type variable gets duplicated. 
Does the type checker treat the separate copies of the constraint as two 
constraints (with the same type variable) which are checked separately?
Or does the type checker only consider one constraint which is checked 
(simultaneously) in different contexts?
Also does it matter if the constraints are on datatype, or even gadt, 
constructors rather than functions?



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