Transformation of Applicative Specifications into Imperative ...

CHAPTER 8. SPECIFICATIONS
out, that using this approach made updating of the map more difficult than
the selected solution.
The TYPES Map
The TYPES map is defined as follows:
TYPES = Binding →m ExpType,
ExpType == Known(type_expr : TypeExpr) | Unknown
The TYPES map maps value names to their corresponding expected type
if known. It is used both during the check for transformability and during
the transformation phase to decide if value names are of the type of interest.
As for the ENV map, the TYPES map is related to a function and not to
the entire specification. The initial value of the TYPES map is computed
in the functions CheckValueDef and TRValueDef when dealing with explicit
function definitions.
8.3.2 The Structure of a Transformation
The main function of the transformer is TRRSLAst which as arguments
takes an applicative RSL AST, a new scheme id and a TRANS map and returns
the corresponding imperative RSL AST, if the applicative RSL AST is
transformable. In some cases the applicative specification cannot be transformed
either because it is not transformable or because it is not within
RSLA. This requires the result of the transformation to be specified as a
variant definition:
TRResult ==
RSLast_transformable(result : RSLAst) |
RSLast_not_transformable
The transformation of an applicative RSL AST is divided into three parts:
1. The TYPINGS map and FUNC map are established.
2. A check for transformability is performed.
3. If the specification is transformable the actual transformation is done.
First the two maps TYPINGS and FUNC are established. Then the
transformer starts from the top of the RSL AST and then moves down the
RSL AST until the whole RSL AST has been processed checking for transformability
and transforming the RSL AST on its way.
In the following the structure of the check for transformability and the
transformation will be described.
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