Programming Research Group A PRETTIER COMPILER-COMPILER: GENERATING HIGHER ORDER PARSERS IN C

Top-down (LL) parsers are easy to express in functional programming languages, but the elegant functional programming model can also serve as an exact prototype for a `real' implementation of the technology in ansi C. The result is a compiler-compiler that takes unlimited lookahead and backtracking, the extended BNF notation, and parameterized grammars with (higher order) metaparameters to the world of C programming. The generated code is standard ansi C and is `plug compatible' with lex-generated lexical analyzers prepared for the unix yacc compiler-compiler. In contrast to yacc, however, the generated code is modular and thus allows parts of scripts to be compiled separately and linked in incrementally, but it remains e cient, as is demonstrated by the example occam parser treated in depth here.