Taming the PL/I syntax

摘要

AbstractIdeally the syntactic part of a PL/I compiler would be generated directly from the semi‐formal definition of ANSI Standard PL/I. A practical approach to this is described, using finite state machines and an LALR parser generator.The parser uses a method due to Aoe which avoids list searching. Adapted for this method the PL/I grammar has 841 states. The parse table generator exploits the freedom to renumber states in a way that improves on previous algorithms for compacting the tables. The parser tables occupy less than 4K byte