Module FlatCurry.Transform.Types
Definition of types used to specify transformations on FlatCurry programs.
Data types for expression transformations
type Path
= [Int]
A path to some subepxression is represented by a list of integers.
type Step
= (String, Path, Expr)
A transformation step consists of a string, a path, and an expression.
type ExprTransformation
= (VarIndex, Path) -> Expr -> (Expr, String, Int)
An expression transformation is a (possibly non-deterministic) operation which takes a pair consisting of a fresh variable index and the position of the expression in the right-hand side and a FlatCurry expression and returns a transformed expression, the name of the applied transformation (just for debugging), and the number of new variables used in the transformation,
type ExprTransformationDet
= (VarIndex, Path) -> Expr -> Maybe (Expr, String, Int)
An deterministic expression transformation is an totally defined operation
which takes a pair consisting of a fresh variable index and the position
of the expression in the right-hand side
and a FlatCurry expression and returns a Maybe
value.
The result is Nothing
if the transformation is not applicable,
otherwise the result consists of the transformed expression,
the name of the applied transformation (for debugging),
and the number of new variables used in the transformation,
Operations to lift simple transformations to general ones
makeT
:: String -> (Expr -> Expr) -> (Int, [Int]) -> Expr -> (Expr, String, Int) 
Lift a simple transformation on expressions to a general
expression transformation (of type ExprTransformation)
where the name of the transformation is provided as the first argument.
makeTDet
:: String -> (Expr -> Maybe Expr) -> (Int, [Int]) -> Expr -> Maybe (Expr, String, Int)
Lift a simple deterministic transformation on expressions to a general
deterministic expression transformation (of type ExprTransformationDet)
where the name of the transformation is provided as the first argument.
Compose deterministic transformations
(<?>)
:: ((Int, [Int]) -> Expr -> Maybe (Expr, String, Int)) -> ((Int, [Int]) -> Expr -> Maybe (Expr, String, Int)) -> (Int, [Int]) -> Expr -> Maybe (Expr, String, Int)
Parallel composition of two deterministic expression transformations where the second transformation is used if the first is not applicable.
combine
:: [(Int, [Int]) -> Expr -> Maybe (Expr, String, Int)] -> (Int, [Int]) -> Expr -> Maybe (Expr, String, Int)
Parallel composition of a sequence of deterministic expression transformations.