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Abstract
This paper deals with a syntax-directed parsing scheme being used in a PL/I compiler for the CDC 6600. It uses a highly restricted grammar of the class LL(1) for efficiency, with an escape hatch for those cases excluded by the grammar. These cases are handled by oracles that can make decisions without a full-scale syntactic analysis. The input to SYNDIPAR, the SYNtax Directed PARser, consists of syntax equations, semantic routines, and token class definitions; the output consists of a PARSE procedure in PL/I together with certain tables. The PARSE procedure works in conjunction with a lexical scanner, designed to allow look-ahead by oracles in a uniform fashion. The actual parsing process takes place through the interpretation of a program compiled by SYNDIPAR for a parsing machine. The instruction set of the parsing machine is described, and an example of the compilation of a syntax equation is given.