Semantic specification using two-level grammars: Blocks, procedures and parameters

Formal specifications are presented for the complete syntax and semantics of an ALGOL-like language fragment, using a recently introduced definitional technique employing two-level grammars (W-grammars). The fragment contains several important features whose dynamic semantics have not previously been treated by means of this technique: block structure, (recursive) procedures, and parameters passed by value, by reference, and by name. The degree of conciseness, clarity, etc., of the specifications is comparable to that obtainable with other approaches to formal seamantics, and it is concluded that two-level grammars must currently be regarded as a competitive approach for progress in language specification.