The Purdue Compiler Construction Tool Set (PCCTS).
PCCTS consists of ANother Tool for Language Recognition (ANTLR), a
DFA-based Lexical analyzer Generator (DLG) and assorted other utilities
designed for the construction of compilers and other language translators.
ANTLR is a parser generator which generates recursive descent parsers which
are easier to debug than the table driven bottom-up parsers created by YACC.
It also provides support for the automatic generation of Abstract Syntax
Trees (AST's).