From PEG to a practical parser

Tool to transcribe Parsing Expression Grammar into a parser written in Java.

Parsing Expression Grammar (PEG) is a way to specify recursive-descent parsers with limited backtracking. The use of backtracking lifts the LL(1) restriction usually imposed by top-down parsers. In addition, PEG can define parsers with integrated lexing.

Unlike some existing parser generators for PEG, the tool does not produce a complex and storage-hungry "packrat parser", but a collection of transparent recursive procedures.

The tool can handle left recursion.

An integral feature of "Mouse" is the mechanism for specifying semantics (also in Java). This makes "Mouse" a convenient tool if one needs an ad-hoc language processor. Being written in Java, the processor is operating-system independent.

Included in the package is PEG Explorer, an interactive tool to investigate the effect of limited backtracking.
Sample grammars for Java & C are available from the Web Site.

Features

• Support for left-recursion. See http://mousepeg.sourceforge.net.
• PEG Explorer: an interactive tool to investigate the effect of limited backtracking. See http://mousepeg.sourceforge.net/explorer.htm.
• Two new operators, ":" and ":!". They simplify definition of keywords, and they enable Explorer to distinguish between keywords and identifiers.

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