[Haskell-cafe] RFE: Extensible algebraic user-defined data types?

Peter Padawitz peter.padawitz at udo.edu
Fri Apr 29 08:51:01 EDT 2005

So many words about a simple thing? I wrote to Dimitry that subtyping in 
O'Haskell and Timber provides exactly what he wants:

data Either a b = Left a  | Right b

data NEither > Either = None

Why has this elegant concept not yet been implemented in standard Haskell?


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