kure-2.16.12: Combinators for Strategic Programming

Copyright (c) 2012--2014 The University of Kansas BSD3 Neil Sculthorpe beta ghc Safe-Inferred Haskell2010

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 a Source

The identity rewrite.

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

An always successful transformation.

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

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 b Source

Lift a transformation to operate on a derived context.

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

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 d Source

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 b Source

Deprecated: Please use `catchesM` instead.

Attempt each transformation 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) a Source

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 a Source

Catch a failing rewrite, making it into an identity.

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

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 a Source

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

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

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

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

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 a Source

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 a Source

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

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

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

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

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 a Source

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 a Source

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) a Source

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

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

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.