Copyright	Copyright (c) 2007--2015 wren gayle romano
License	BSD
Maintainer	wren@community.haskell.org
Stability	experimental
Portability	semi-portable (MPTCs,...)
Safe Haskell	None
Language	Haskell98

Control.Unification.IntVar

Description

This module defines a state monad for functional pointers represented by integers as keys into an IntMap. This technique was independently discovered by Dijkstra et al. This module extends the approach by using a state monad transformer, which can be made into a backtracking state monad by setting the underlying monad to some MonadLogic (part of the logict library, described by Kiselyov et al.).

Atze Dijkstra, Arie Middelkoop, S. Doaitse Swierstra (2008) Efficient Functional Unification and Substitution, Technical Report UU-CS-2008-027, Utrecht University.
Oleg Kiselyov, Chung-chieh Shan, Daniel P. Friedman, and Amr Sabry (2005) Backtracking, Interleaving, and Terminating Monad Transformers, ICFP.

Synopsis

newtype IntVar = IntVar Int
data IntBindingState t
data IntBindingT t m a
runIntBindingT :: IntBindingT t m a -> m (a, IntBindingState t)
evalIntBindingT :: Monad m => IntBindingT t m a -> m a
execIntBindingT :: Monad m => IntBindingT t m a -> m (IntBindingState t)

Documentation

newtype IntVar Source #

A "mutable" unification variable implemented by an integer. This provides an entirely pure alternative to truly mutable alternatives (like STVar), which can make backtracking easier.

N.B., because this implementation is pure, we can use it for both ranked and unranked monads.

Constructors

IntVar Int

Instances

Instances details

Eq IntVar Source #
Instance details Defined in Control.Unification.IntVar Methods (==) :: IntVar -> IntVar -> Bool # (/=) :: IntVar -> IntVar -> Bool #
Show IntVar Source #
Instance details Defined in Control.Unification.IntVar Methods showsPrec :: Int -> IntVar -> ShowS # show :: IntVar -> String # showList :: [IntVar] -> ShowS #
Variable IntVar Source #
Instance details Defined in Control.Unification.IntVar Methods getVarID :: IntVar -> Int Source #
(Unifiable t, Applicative m, Monad m) => RankedBindingMonad t IntVar (IntRBindingT t m) Source #
Instance details Defined in Control.Unification.Ranked.IntVar Methods lookupRankVar :: IntVar -> IntRBindingT t m (Rank t IntVar) Source # incrementRank :: IntVar -> IntRBindingT t m () Source # incrementBindVar :: IntVar -> UTerm t IntVar -> IntRBindingT t m () Source #
(Unifiable t, Applicative m, Monad m) => BindingMonad t IntVar (IntBindingT t m) Source #
Instance details Defined in Control.Unification.IntVar Methods lookupVar :: IntVar -> IntBindingT t m (Maybe (UTerm t IntVar)) Source # freeVar :: IntBindingT t m IntVar Source # newVar :: UTerm t IntVar -> IntBindingT t m IntVar Source # bindVar :: IntVar -> UTerm t IntVar -> IntBindingT t m () Source #
(Unifiable t, Applicative m, Monad m) => BindingMonad t IntVar (IntRBindingT t m) Source #
Instance details Defined in Control.Unification.Ranked.IntVar Methods lookupVar :: IntVar -> IntRBindingT t m (Maybe (UTerm t IntVar)) Source # freeVar :: IntRBindingT t m IntVar Source # newVar :: UTerm t IntVar -> IntRBindingT t m IntVar Source # bindVar :: IntVar -> UTerm t IntVar -> IntRBindingT t m () Source #

data IntBindingState t Source #

Binding state for IntVar.

Instances

Instances details

Show (t (UTerm t IntVar)) => Show (IntBindingState t) Source #
Instance details Defined in Control.Unification.IntVar Methods showsPrec :: Int -> IntBindingState t -> ShowS # show :: IntBindingState t -> String # showList :: [IntBindingState t] -> ShowS #
Monad m => MonadState (IntBindingState t) (IntBindingT t m) Source #
Instance details Defined in Control.Unification.IntVar Methods get :: IntBindingT t m (IntBindingState t) # put :: IntBindingState t -> IntBindingT t m () # state :: (IntBindingState t -> (a, IntBindingState t)) -> IntBindingT t m a #

data IntBindingT t m a Source #

A monad for storing IntVar bindings, implemented as a StateT. For a plain state monad, set m = Identity; for a backtracking state monad, set m = Logic.

Instances

Instances details

(Unifiable t, Applicative m, Monad m) => BindingMonad t IntVar (IntBindingT t m) Source #
Instance details Defined in Control.Unification.IntVar Methods lookupVar :: IntVar -> IntBindingT t m (Maybe (UTerm t IntVar)) Source # freeVar :: IntBindingT t m IntVar Source # newVar :: UTerm t IntVar -> IntBindingT t m IntVar Source # bindVar :: IntVar -> UTerm t IntVar -> IntBindingT t m () Source #
MonadTrans (IntBindingT t) Source #
Instance details Defined in Control.Unification.IntVar Methods lift :: Monad m => m a -> IntBindingT t m a #
Monad m => MonadState (IntBindingState t) (IntBindingT t m) Source #
Instance details Defined in Control.Unification.IntVar Methods get :: IntBindingT t m (IntBindingState t) # put :: IntBindingState t -> IntBindingT t m () # state :: (IntBindingState t -> (a, IntBindingState t)) -> IntBindingT t m a #
Monad m => Monad (IntBindingT t m) Source #
Instance details Defined in Control.Unification.IntVar Methods (>>=) :: IntBindingT t m a -> (a -> IntBindingT t m b) -> IntBindingT t m b # (>>) :: IntBindingT t m a -> IntBindingT t m b -> IntBindingT t m b # return :: a -> IntBindingT t m a #
Functor m => Functor (IntBindingT t m) Source #
Instance details Defined in Control.Unification.IntVar Methods fmap :: (a -> b) -> IntBindingT t m a -> IntBindingT t m b # (<$) :: a -> IntBindingT t m b -> IntBindingT t m a #
(Functor m, Monad m) => Applicative (IntBindingT t m) Source #
Instance details Defined in Control.Unification.IntVar Methods pure :: a -> IntBindingT t m a # (<>) :: IntBindingT t m (a -> b) -> IntBindingT t m a -> IntBindingT t m b # liftA2 :: (a -> b -> c) -> IntBindingT t m a -> IntBindingT t m b -> IntBindingT t m c # (>) :: IntBindingT t m a -> IntBindingT t m b -> IntBindingT t m b # (<*) :: IntBindingT t m a -> IntBindingT t m b -> IntBindingT t m a #
(Functor m, MonadPlus m) => Alternative (IntBindingT t m) Source #
Instance details Defined in Control.Unification.IntVar Methods empty :: IntBindingT t m a # (<\|>) :: IntBindingT t m a -> IntBindingT t m a -> IntBindingT t m a # some :: IntBindingT t m a -> IntBindingT t m [a] # many :: IntBindingT t m a -> IntBindingT t m [a] #
MonadPlus m => MonadPlus (IntBindingT t m) Source #
Instance details Defined in Control.Unification.IntVar Methods mzero :: IntBindingT t m a # mplus :: IntBindingT t m a -> IntBindingT t m a -> IntBindingT t m a #
MonadLogic m => MonadLogic (IntBindingT t m) Source #
Instance details Defined in Control.Unification.IntVar Methods msplit :: IntBindingT t m a -> IntBindingT t m (Maybe (a, IntBindingT t m a)) # interleave :: IntBindingT t m a -> IntBindingT t m a -> IntBindingT t m a # (>>-) :: IntBindingT t m a -> (a -> IntBindingT t m b) -> IntBindingT t m b # ifte :: IntBindingT t m a -> (a -> IntBindingT t m b) -> IntBindingT t m b -> IntBindingT t m b # once :: IntBindingT t m a -> IntBindingT t m a # lnot :: IntBindingT t m a -> IntBindingT t m () #

runIntBindingT :: IntBindingT t m a -> m (a, IntBindingState t) Source #

evalIntBindingT :: Monad m => IntBindingT t m a -> m a Source #

N.B., you should explicitly apply bindings before calling this function, or else the bindings will be lost

execIntBindingT :: Monad m => IntBindingT t m a -> m (IntBindingState t) Source #