Conjure.Red

This module is part of Conjure.

This defines functions that deal with recursive descent and deconstructions

Documentation

conjureIsDeconstruction :: Conjurable f => f -> Int -> Expr -> Bool

Checks if an expression is a deconstruction.

There should be a single hole in the expression.

It should decrease the size of all arguments that have a size greater than 0.

descends :: (Expr -> Expr -> Bool) -> Expr -> Expr -> Bool

Returns whether a non-empty subset of arguments descends arguments by deconstruction.

> descends isDec (xxs -++- yys) (xxs -++- tail' yys)
True

> descends isDec (xxs -++- yys) (xxs -++- yys)
False

> descends isDec (xxs -++- yys) (head' xxs -:- tail xxs  -++-  head' yys -:- tail yys)
False

candidateDeconstructionsFrom :: Expr -> [Expr]

Compute candidate deconstructions from an Expr.

This is used in the implementation of candidateDefnsC followed by conjureIsDeconstruction.

> candidateDeconstructionsFrom (xx `mod'` yy)
[ _ `mod` y
, x `mod` _
]

To be constrasted with candidateDeconstructionsFromHoled.

candidateDeconstructionsFromHoled :: Expr -> [Expr]

Compute candidate deconstructions from an Expr.

This is used in the implementation of candidateExprs followed by conjureIsDeconstruction.

This is similar to canonicalVariations but always leaves a hole of the same return type as the given expression.

> candidateDeconstructionsFrom (i_ `mod'` i_)
[ _ `mod` x
, x `mod` _
]

To be contrasted with candidateDeconstructionsFrom