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 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 http://www.eyrie.org/~zednenem/