Hi, Thank you, works indeed with the strict ST monad. Didn't think of that. But makes kind of sense not to define these instances, since unboxed values cannot have their computation delayed. It's a bit unfortunate, however, that a single use of an unboxed array "forces" the whole state thread to become strict.
-----Original Message----- From: d4ve.menen...@gmail.com [mailto:d4ve.menen...@gmail.com] On Behalf Of David Menendez Sent: Mittwoch, 22. Juli 2009 00:53 To: Christian Klauser Cc: glasgow-haskell-users@haskell.org Subject: Re: "Could not deduce (MArray (STUArray s) Int (ST s)) from context ()" when applying runST On Tue, Jul 21, 2009 at 5:30 PM, Christian Klauser<ch27...@gmail.com> wrote: > Hi, I'm in the process of learning haskell and came across this problem: > > Using `Glasgow Haskell Compiler, Version 6.10.4, for Haskell 98, stage 2 > booted by GHC version 6.10.1` > > Common beginning of the file > ============================ > {-# LANGUAGE FlexibleContexts #-} > > module UPSO where > > import Control.Monad(forM,forM_) > import Control.Monad.ST.Lazy (ST,runST) This works if I replace Control.Monad.ST.Strict instead of Control.Monad.ST.Lazy. The problem is that the MArray instances are declared for the strict ST monad; there appear to be no corresponding instances for the lazy ST monad. -- Dave Menendez <d...@zednenem.com> <http://www.eyrie.org/~zednenem/> _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
