Mutable arrays in Haskell 98

[Malcolm Wallace]

José Romildo Malaquias <romildo@uber.com.br> writes:

> I would like to use muttable arrays in Haskell 98, with the GHC
> _and_ NHC98 compilers. By muttable arrays I mean arrays with
> in-place updates, as with the MArray arrays (which are not
> Haskell 98 conformant) found in GHC. Is such array implmentation
> available?

Both compilers have libraries supporting the `IOArray' type,
implemented with in-place update, although obviously the operations
must be threaded through the IO monad.

module IOExtras		-- called IOExts in ghc
  ( ... 
  , IOArray             -- data IOArray ix elt -- mutable arrays
  , newIOArray          -- :: Ix ix => (ix,ix) -> elt -> IO (IOArray ix elt)
  , boundsIOArray       -- :: Ix ix => IOArray ix elt -> (ix, ix)
  , readIOArray         -- :: Ix ix => IOArray ix elt -> ix -> IO elt
  , writeIOArray        -- :: Ix ix => IOArray ix elt -> ix -> elt -> IO ()
  , freezeIOArray       -- :: Ix ix => IOArray ix elt -> IO (Array ix elt)

  , module Ix           -- re-export Ix for the benefit of IOArrays
    -- instance Eq (IOArray ix elt)
  )

Regards,
    Malcolm