Re: [Haskell] question about a failure to generalize

On Mon, Sep 17, 2007 at 04:15:10PM +1200, Tom Pledger wrote:

Norman Ramsey wrote: : | This code fails to compile because the compiler is willing to | use 'fold' at only one type (CmmExpr as it happens) :

When it failed to compile, was

fold = foldRegsUsed

a top-level declaration in the module, rather than local to foldRegsUsed?

If so, try working around the monomorphism restriction by changing from a pattern binding to a function binding.

fold f = foldRegsUsed f

The monomorphism restriction is not affected by top-level-or-not, see sections 4.5.1 and 4.5.5 in the Haskell 98 Language and Libraries Report. Stefan