Probably a weird idea but could this be useful?
class (Monad m) => Stream s m t | s -> t where
uncons :: s -> m (m (t,s))
for example:
instance (Monad m) => Stream [t] m t where
uncons [] = return $ fail "uncons []"
uncons (t:ts) = return $ return (t,ts)
One small advantage is that Streams can have custom error messages
when there's no input.
Also, using 'uncons' could be as simple as: 'join . uncons'.
Bas
On Feb 2, 2008 6:15 AM, Derek Elkins
[Now with 100% more correct darcs get URLs.]
I'm currently getting Paolo Martini's Google Summer of Code project, an updated version of Parsec, into a releasable state, and I will be maintaining it for at least a while.
Paolo's major additions are: * The Parser monad has been generalized into a Parser monad transformer * The parsers have been generalized to work over a stream of any type, in particular, with bytestrings.
I have made a few minor additions as well: * There is Haddock documentation for almost all functions * The Parser monad now has Applicative/Alternative instances
Currently, I am looking for people to give it a go reporting any bugs in the library or documentation, troubles building it, or changes/features they would like. I'm also interested in performance information.
Most old Parsec code should be relatively easy but not trivial to port. There is a darcs repository on code.haskell.org. If nothing comes up, I'll put a package on Hackage in about a week or so.
To get the code: darcs get http://code.haskell.org/parsec3
To build it, the standard cabal commands should work: http://haskell.org/haskellwiki/Cabal/How_to_install_a_Cabal_package
Alternatively, you can use the cabal-install application: http://hackage.haskell.org/trac/hackage/wiki/CabalInstall
The documentation can be generated also via the normal cabal routine, or via cabal-install.
The Text.Parsec modules should be preferred to the Text.ParserCombinators.Parsec modules.
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