documentation: 
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flatcurry-transform
===================
This package provides a framework to support transformations on FlatCurry
programs.
A simple transformation on a FlatCurry expression is an operation
of type
Expr -> Expr
which 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 _) = e
Note 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 e2
The 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" removeQuestionRule
The 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`.
Examples
--------
The subdirectory `examples` contains various example transformations
in the programs
- `Transformations.curry` (functional logic transformations as described above)
- `DetTransformations.curry` (deterministic transformations)
Documentation
-------------
More details explaining the ideas and advantages of this kind of
program transformations are available in a
[paper on functional logic program transformations](https://arxiv.org/abs/2601.13224).
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