Restricted Data Types Now

Jim Apple jbapple+haskell-prime at
Sun Feb 12 11:50:16 EST 2006

On 2/8/06, oleg at <oleg at> wrote:
> It seems we can emulate the restricted data types in existing
> Haskell.
> > {-# OPTIONS -fglasgow-exts #-}
> > {-# OPTIONS -fallow-undecidable-instances #-}

Indicates that we will no longer need undecidable instances for this.
Since we can check termination, and this simulates restricted data
types with no core language changes, why not do it?

Why not change the libraries in Haskell' to put formerly polymorphic
variables as class parameters?


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