On 10 March 2011 18:24, Yves Parès <limestr...@gmail.com> wrote: > Why has the operator (.) troubles with a type like (forall s. ST s a)? > > Why can't it match the type 'b' in (.) definition?
As explained by the email from SPJ that I linked to, instantiating a type variable (like 'b') with a polymorphic type (like 'forall s. ST s a' ) is called impredicative polymorphism. Since GHC-7 this is not supported any more because it was to complicated. Bas _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
