* - http://www.grabmueller.de/martin/www/pub/Transformers.pdf
* - http://en.wikibooks.org/wiki/Haskell/Monad_transformers
*
- * Licensing: MIT (if that's compatible with the ghc sources).
+ * Licensing: MIT (if that's compatible with the ghc sources this is partly
+ * derived from)
*)
exception Undefined