A small compatibility shim exposing the new types from transformers 0.3 and 0.4 to older Haskell platforms.

Version on this page:
LTS Haskell 22.29:0.7.2
Stackage Nightly 2024-07-15:0.7.2
Latest on Hackage:0.7.2

See all snapshots transformers-compat appears in

BSD-3-Clause licensed by Edward A. Kmett
Maintained by Edward A. Kmett
This version can be pinned in stack with:transformers-compat-,2302

Module documentation for

There are no documented modules for this package.


Build Status

This provides a thin compatibility shim on top of transformers-0.2 to add the types that were added in transformers-0.3.

This enables users to maintain haskell-platform compatibility, while still gaining access ot the new functionality.

Contact Information

Contributions and bug reports are welcome!

Please feel free to contact me through github or on the #haskell IRC channel on

-Edward Kmett



  • transformers 0.4.1 compatibility


  • Added the instances for Data.Functor.Classes from transformers 0.4
  • Switched Control.Applicative.Backwards and Data.Functor.Reverse to the split constructor/accessor style from transformers 0.4.


  • Added the new types and classes from transformers 0.4

  • Wrote a better synopsis


  • Updated to trick cabal into building an empty libHStransformers-compat-0.1.a on GHC 7.6.


  • Repository initialized by pulling the transformers-0.2 compatibility layer out of lens.