Copyright | (c) Andy Gill 2001, (c) Oregon Graduate Institute of Science and Technology, 2002 |
---|---|
License | BSD-style (see the file libraries/base/LICENSE) |
Maintainer | libraries@haskell.org |
Stability | experimental |
Portability | portable |
Safe Haskell | Trustworthy |
Language | Haskell2010 |
Monadic fixpoints.
For a detailed discussion, see Levent Erkok's thesis, Value Recursion in Monadic Computations, Oregon Graduate Institute, 2002.
class Monad m => MonadFix m where Source
Monads having fixed points with a 'knot-tying' semantics. Instances of MonadFix
should satisfy the following laws:
mfix (return . h) = return (fix h)
mfix (\x -> a >>= \y -> f x y) = a >>= \y -> mfix (\x -> f x y)
mfix (liftM h . f) = liftM h (mfix (f . h))
, for strict h
.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.
mfix :: (a -> m a) -> m a Source
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.
fix f
is the least fixed point of the function f
, i.e. the least defined x
such that f x = x
.
© The University of Glasgow and others
Licensed under a BSD-style license (see top of the page).
https://downloads.haskell.org/~ghc/7.10.3/docs/html/libraries/base-4.8.2.0/Control-Monad-Fix.html