[haskell-beginners] Ralf Laemmel's riddle on surviving without the monad transformation library

[C K Kashyap]

Hi,

Can someone provide me the solution to the following riddle that Ralf
asked in his lecture at
http://channel9.msdn.com/Shows/Going+Deep/C9-Lectures-Dr-Ralf-Lmmel-Advanced-Functional-Programming-Evolution-of-an-Interpreter

Riddle: define a custom made monad (only involving (->) and Either
String) to survive without the monad transformation library.


-- 
Regards,
Kashyap