[Haskell-cafe] ANN: monad-bool 0.1
johnw at fpcomplete.com
Wed Jan 23 07:02:01 CET 2013
>>>>> Roman Cheplyaka <roma at ro-che.info> writes:
> - what do you need unsafeCoerce for?
Ok, after much discussion with edwardk and shachaf, I came to realize a few
1. The functionality of my two monads 'AndM' and 'OrR' can be boiled down to
two helper functions inside EitherT:
returnIf :: Monad m => Bool -> e -> EitherT e m ()
returnIf p a = if p then left a else right ()
returnUnless :: Monad m => Bool -> e -> EitherT e m ()
returnUnless p = returnIf (not p)
These let you short-circuit monadic computations, returning the
short-circuiting value as a Left; or as a Right if it reaches the end.
2. The 'shortcircuit' library already provides short-circuiting variants of
&& and || that work just like Python's and Ruby's. In fact, I think I'll
talk to aristid about merging my Monoid definitions into that library.
Here are the updated docs:
I'll ask Ross Paterson to deprecate monad-bool. And in future, I'll seek
review here first before uploading.
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