transformers versus mtl

Sittampalam, Ganesh ganesh.sittampalam at
Sat Mar 21 12:19:05 EDT 2009

Ross Paterson wrote:
> The combination transformers + monads-fd is close to a compatible
> replacement for mtl at the source level, except that State, Writer,
> etc are now type synonyms, which will break some code. Of course the
> package names are also different.  We can't just rename monads-fd as
> mtl-2.0, because Control.Monad.Identity and Control.Monad.Trans are
> in the transformers package.  But we could make a compatibility
> version of mtl along the lines of base3-compat.  (And we need to
> rename the modules in monads-tf.)

The compatibility layer could continue to export the old separate types
for State, Writer, etc, couldn't it?

Are there any problems with adding transformers and monads-fd to
extralibs pending the Haskell Platform being ready?



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