kure-2.16.1: Combinators for Strategic Programming

Portability ghc beta Neil Sculthorpe Safe-Inferred

Language.KURE.Combinators.Transform

Description

This module provides a variety of combinators over `Transform` and `Rewrite`.

Synopsis

# Transformation Combinators

idR :: Monad m => Rewrite c m aSource

The identity rewrite.

successT :: Monad m => Transform c m a ()Source

An always successful transformation.

contextT :: Monad m => Transform c m a cSource

Extract the current context.

exposeT :: Monad m => Transform c m a (c, a)Source

Expose the current context and value.

liftContext :: (c -> c') -> Transform c' m a b -> Transform c m a bSource

Lift a transformation to operate on a derived context.

readerT :: (a -> Transform c m a b) -> Transform c m a bSource

Look at the argument to the transformation before choosing which `Transform` to use.

resultT :: (m b -> n d) -> Transform c m a b -> Transform c n a dSource

Convert the monadic result of a transformation into a result in another monad.

catchesT :: MonadCatch m => [Transform c m a b] -> Transform c m a bSource

Attempt each trransformation until one succeeds, then return that result and discard the rest of the transformations.

mapT :: (Traversable t, Monad m) => Transform c m a b -> Transform c m (t a) (t b)Source

Map a transformation over a list.

joinT :: Transform c m (m a) aSource

An identity transformation that resembles a monadic `join`.

guardT :: Monad m => Transform c m Bool ()Source

Fail if the Boolean is False, succeed if the Boolean is True.

# Rewrite Combinators

tryR :: MonadCatch m => Rewrite c m a -> Rewrite c m aSource

Catch a failing rewrite, making it into an identity.

andR :: (Foldable f, Monad m) => f (Rewrite c m a) -> Rewrite c m aSource

Perform a collection of rewrites in sequence, requiring all to succeed.

orR :: (Functor f, Foldable f, MonadCatch m) => f (Rewrite c m a) -> Rewrite c m aSource

Perform a collection of rewrites in sequence, succeeding if any succeed.

(>+>) :: MonadCatch m => Rewrite c m a -> Rewrite c m a -> Rewrite c m aSource

Perform two rewrites in sequence, succeeding if one or both succeed.

repeatR :: MonadCatch m => Rewrite c m a -> Rewrite c m aSource

Repeat a rewrite until it fails, then return the result before the failure. Requires at least the first attempt to succeed.

acceptR :: Monad m => (a -> Bool) -> Rewrite c m aSource

Look at the argument to a rewrite, and choose to be either `idR` or a failure.

acceptWithFailMsgR :: Monad m => (a -> Bool) -> String -> Rewrite c m aSource

As `acceptR`, but takes a custom failure message.

accepterR :: Monad m => Transform c m a Bool -> Rewrite c m aSource

A generalisation of `acceptR` where the predicate is a `Transform`.

changedR :: (MonadCatch m, Eq a) => Rewrite c m a -> Rewrite c m aSource

Makes an rewrite fail if the result value equals the argument value.

changedByR :: MonadCatch m => (a -> a -> Bool) -> Rewrite c m a -> Rewrite c m aSource

Makes a rewrite fail if the result value and the argument value satisfy the equality predicate. This is a generalisation of `changedR`. `changedR = changedByR (==)`

sideEffectR :: Monad m => (c -> a -> m ()) -> Rewrite c m aSource

An identity rewrite with side-effects.

## anyR Support

These are useful when defining congruence combinators that succeed if any child rewrite succeeds. See the "Expr" example, or the HERMIT package.

data AnyR m a Source

The `AnyR` transformer, in combination with `wrapAnyR` and `unwrapAnyR`, causes a sequence of rewrites to succeed if at least one succeeds, converting failures to identity rewrites.

Instances

wrapAnyR :: MonadCatch m => Rewrite c m a -> Rewrite c (AnyR m) aSource

Wrap a `Rewrite` using the `AnyR` monad transformer.

unwrapAnyR :: Monad m => Rewrite c (AnyR m) a -> Rewrite c m aSource

Unwrap a `Rewrite` from the `AnyR` monad transformer.

## oneR Support

These are useful when defining congruence combinators that succeed if one child rewrite succeeds (and the remainder are then discarded). See the "Expr" example, or the HERMIT package.

data OneR m a Source

The `OneR` transformer, in combination with `wrapOneR` and `unwrapOneR`, causes a sequence of rewrites to only apply the first success, converting the remainder (and failures) to identity rewrites.

Instances

Wrap a `Rewrite` using the `OneR` monad transformer.
Unwrap a `Rewrite` from the `OneR` monad transformer.