Agile Parsing in TXL

Syntactic analysis forms a foundation of many source analysis and reverse engineering tools. However, a single standard grammar is not always appropriate for all source analysis and manipulation tasks. Small custom modifications to the grammar can make the programs used to implement these tasks simpler, clearer and more efficient. This leads to a new paradigm for programming these tools: agile parsing. In agile parsing the effective grammar used by a particular tool is a combination of two parts: the standard base grammar for the input language, and a set of explicit grammar overrides that modify the parse to support the task at hand. This paper introduces the basic techniques of agile parsing in TXL and discusses several industry proven techniques for exploiting agile parsing in software source analysis and transformation.