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[pbrowne <Patrick.Browne AT comp.dit.ie>]

hi,
I have a question concerning Wadler's expression problem[1] for
algebraic data types. In relation to Haskells type classes is easy to
add a new operations on existing data types, it requires only the
definition of a new function. All the old functions on those types
continue to work unchanged. On the other hand, it is difficult to add
new structure to an existing data type: it requires the addition of a
new constructor for the existing data type.

Questions:
1)Does expression problem exist in Maude?
2)If it does not exist in Maude, is there an illustrative example available?


Pat

[1]http://en.wikipedia.org/wiki/Expression_Problem