[Haskell-cafe] Guards with do notation?

Joachim Breitner mail at joachim-breitner.de
Tue Oct 24 04:27:37 EDT 2006


Am Dienstag, den 24.10.2006, 00:44 +0300 schrieb Misha Aizatulin:
> hello all,
>    why is it not possible to use guards in do-expressions like
>        do
>          (a, b) | a == b <- getPair
>          return "a and b are equal"

Probably because it is not well-defined for all Monad what a failure is,
i.e. what to do in the other case. or something. Just my guess.

Joachim "nomeata" Breitner
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  Debian Developer: nomeata at debian.org

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