FlatCurry.Transform.Types
FlatCurry.Transform.Exec
FlatCurry.Transform.ExecDet
FlatCurry.Transform.ExecND
This package provides a framework to support transformations on FlatCurry programs. A simple transformation on a FlatCurry expression is an operation of type
Expr -> Exprwhich can be partially defined and also non-deterministic. For instance, a transformation to remove type annotations can be defined by
unTypeRule :: Expr -> Expr
unTypeRule (Typed e _) = eNote that this operation is partially defined since it fails on
non-"Typed" expressions. However, it is a natural
representation of the idea of this transformation.
Similarly, a transformation to remove occurrences of the prelude
operation "?" by replacing them by the choice construct of
FlatCurry can be defined by
removeQuestionRule :: Expr -> Expr
removeQuestionRule (Comb FuncCall ("Prelude","?") [e1,e2]) = Or e1 e2The library FlatCurry.Transform.Types defines the type
ExprTransformation to support more complex transformations
which might require fresh variables or the subterm position. The
auxiliary operation makeT lifts a simple transformation
into such a general transformation where a name must be provided which
is used during debugging. For instance, we can define
unType :: ExprTransformation
unType = makeT "UNTYPE" unTypeRule
removeQuestion :: ExprTransformation
removeQuestion = makeT "REMOVE-?-CAll" removeQuestionRuleThe library FlatCurry.Transform.Exec defines the
operation transformExpr to apply a transformation as long
as possible. If a transformation is non-deterministic, as
(unType ? removeQuestion)all possible transformations are applied in an unspecified order. The
examples (see below) contain code snippets showing the use of the
operation transformExpr.
The subdirectory examples contains various example
transformations in the programs
Transformations.curry (functional logic transformations
as described above)DetTransformations.curry (deterministic
transformations)More details explaining the ideas and advantages of this kind of program transformations are available in a paper on functional logic program transformations.