Data.Generics.Strafunski.StrategyLib.StrategyPrelude

This module is part of StrategyLib, a library of functional strategy combinators, including combinators for generic traversal. This module is basically a wrapper for the strategy primitives plus some extra basic strategy combinators that can be defined immediately in terms of the primitive ones.

Documentation

module Data.Generics.Strafunski.StrategyLib.Models.Deriving.StrategyPrimitives

Useful defaults for strategy update (see adhocTU and adhocTP).

idTP :: Monad m => TP m

Type-preserving identity. Returns the incoming term without change.

failTP :: MonadPlus m => TP m

Type-preserving failure. Always fails, independent of the incoming term. Uses MonadPlus to model partiality.

failTU :: MonadPlus m => TU a m

Type-unifying failure. Always fails, independent of the incoming term. Uses MonadPlus to model partiality.

constTU :: Monad m => a -> TU a m

Type-unifying constant strategy. Always returns the argument value a, independent of the incoming term.

compTU :: Monad m => m a -> TU a m

Type-unifying monadic constant strategy. Always performs the argument computation a, independent of the incoming term. This is a monadic variation of constTU.

Lift a function to a strategy type with failure as default

monoTP :: (Term a, MonadPlus m) => (a -> m a) -> TP m

Apply the monomorphic, type-preserving argument function, if its input type matches the input term's type. Otherwise, fail.

monoTU :: (Term a, MonadPlus m) => (a -> m b) -> TU b m

Apply the monomorphic, type-unifying argument function, if its input type matches the input term's type. Otherwise, fail.

Function composition

dotTU :: Monad m => (a -> b) -> TU a m -> TU b m

Sequential ccomposition of monomorphic function and type-unifying strategy. In other words, after the type-unifying strategy s has been applied, the monomorphic function f is applied to the resulting value.

op2TU :: Monad m => (a -> b -> c) -> TU a m -> TU b m -> TU c m

Parallel combination of two type-unifying strategies with a binary combinator. In other words, the values resulting from applying the type-unifying strategies are combined to a final value by applying the combinator o.

Reduce a strategy's performance to its effects

voidTP :: Monad m => TP m -> TU () m

Reduce a type-preserving strategy to a type-unifying one that ignores its result term and returns void, but retains its monadic effects.

voidTU :: Monad m => TU u m -> TU () m

Reduce a type-unifying strategy to a type-unifying one that ignores its result value and returns void, but retains its monadic effects.

Shape test combinators

con :: MonadPlus m => TP m

Test for constant term, i.e. having no subterms.

com :: MonadPlus m => TP m

Test for compound term, i.e. having at least one subterm.