ANTLR, ANother Tool for Language Recognition, (formerly PCCTS) is a language tool that provides a framework for constructing recognizers, compilers, and translators from grammatical descriptions containing Java, C#, C++, or Python actions. ANTLR provides excellent support for tree construction, tree walking, and translation. There are currently about 5,000 ANTLR source downloads a month.

URL: http://www.antlr.org/
Licence: Proprietary