Dynamic parametric rules

[CordyJ]

There is, on rare occasions, a use for parametric rules to simplify code. While implementing fully type-checked parametric rules would be a big project with very little payoff, simple parametric rules would probably serve most applications.

Example:

rule applyRuleToEachStatementMentioning VarId [id] RuleId [id]
    replace $ [statement]
        Statement [statement]
    % A simple example constraint - in practice contraints could be as complex as we want
    skipping [statement]
    deconstruct * [id] S
        VarId
    by
        Statement [RuleId]
end rule

[CordyJ]

Along the same lines, parameteric types would also be useful, most often in generated transformations using polymorphic grammars ([any]). Example:

rule removeOuterStatements TypeId [id]
    skipping [TypeId]
    replace [statement*]
        S [statement]
        MoreS [statement*]
    by
        MoreS
end rule

Then remove statements outside loops would be:

    Statements [removeOuterStatements 'loop_statement]

And remove statements outside ifs would be:

    Statements [removeOuterStatements 'if_statement]