#2309: containers: specialize functions that fail in a Monad to Maybe

Twan van Laarhoven twanvl at gmail.com
Sat May 24 20:26:36 EDT 2008

Ross Paterson wrote:
> The proposal is to change these signatures back, specializing them
> to Maybe.

To retain most of the convenience I would propose we use MonadPlus instead, 
which is arguably where fail should have been put in the first place (*).


(*) Actually in a superclass MonadZero, but let's work with what we have now.

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