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| Control.Monad.Fix | | Portability | portable | | Stability | experimental | | Maintainer | libraries@haskell.org |
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| Description |
Monadic fixpoints.
For a detailed discussion, see Levent Erkok's thesis,
Value Recursion in Monadic Computations, Oregon Graduate Institute, 2002.
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| Synopsis |
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| Documentation |
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| class Monad m => MonadFix m where |
Monads having fixed points with a 'knot-tying' semantics.
Instances of MonadFix should satisfy the following laws:
- purity
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mfix (return . h) = return (fix h)
- left shrinking (or tightening)
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mfix (\x -> a >>= \y -> f x y) = \y -> mfix (\x -> f x y)
- sliding
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mfix (liftM h . f) = liftM h (mfix (f . h)),
for strict h.
- nesting
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mfix (\x -> mfix (\y -> f x y)) = mfix (\x -> f x x)
This class is used in the translation of the recursive do notation
supported by GHC and Hugs.
| | | Methods | | mfix :: (a -> m a) -> m a | | The fixed point of a monadic computation.
mfix f executes the action f only once, with the eventual
output fed back as the input. Hence f should not be strict,
for then mfix f would diverge.
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| |  Instances | |
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| fix :: (a -> a) -> a |
| fix f is the least fixed point of the function f,
i.e. the least defined x such that f x = x.
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| Produced by Haddock version 0.7 |
