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# peg/leg — recursive-descent parser generators for C `peg` and `leg` are tools for generating recursive-descent parsers: programs that perform pattern matching on text. They processes a Parsing Expression Grammar (PEG)[Ford 2004] to produce a program that recognises legal sentences of that grammar. `peg` processes PEGs written using the original syntax described by Ford. `leg` processes PEGs written using slightly different syntax and conventions that are intended to make it an attractive replacement for parsers built with `lex` and `yacc`. Unlike `lex` and `yacc`, `peg` and `leg` support unlimited backtracking, provide ordered choice as a means for disambiguation, and can combine scanning (lexical analysis) and parsing (syntactic analysis) into a single activity. `peg` is distributed under the MIT license. It will not infect your project with a contagious <strike>license</strike> disease if you decide to modify it for your own use. The parser generators that `peg` creates are unencumbered and you are free to use and/or distribute them any way you like. `peg`/`leg` is copyright (c) 2007 by Ian Piumarta. ## References * `peg`/`leg` manual page: [peg.1.html][1] * [Ford 2004] Bryan Ford, [*Parsing Expression Grammars: A Recognition-Based Syntactic Foundation*][2]. ACM SIGPLAN Symposium on Principles of Programming Languages (POPL), 2004. [1]: http://piumarta.com/software/peg/peg.1.html "peg/leg manual" [2]: http://bford.info/pub/lang/peg "Parsing Expression Grammars: A Recognition-Based Syntactic Foundation" ## Version history * **0.1.7** ([zip](peg/zipball/0.1.7), [tar.gz](peg/tarball/0.1.7)) — 2011-11-25 Fix matching of 8-bit chars to allow utf-8 sequences in matching expressions (thanks to Grégory Pakosz). * **0.1.6** ([zip](peg/zipball/0.1.6), [tar.gz](peg/tarball/0.1.6)) — 2011-11-24 Allow octal escapes in character classes. * **0.1.5** ([zip](peg/zipball/0.1.5), [tar.gz](peg/tarball/0.1.5)) — 2011-11-24 Remove dwarf sym dirs when cleaning. Fix size calculation when resizing text buffers. Backslash can be escaped. * **0.1.4** ([zip](peg/zipball/0.1.4), [tar.gz](peg/tarball/0.1.4)) — 2009-08-26 Fix match of a single single quote character. Rename `getline` -> `nextline` to avoid C namespace conflict. * **0.1.3** ([zip](peg/zipball/0.1.3), [tar.gz](peg/tarball/0.1.3)) — 2007-09-13 Allow matched braces inside `leg` actions. Handle empty rules. Handle empty grammars. * **0.1.2** ([zip](peg/zipball/0.1.2), [tar.gz](peg/tarball/0.1.2)) — 2007-08-31 Grow buffers while (not if) they are too small. Remove dependencies on grammar files. Add more basic examples. * **0.1.1** ([zip](peg/zipball/0.1.1), [tar.gz](peg/tarball/0.1.1)) — 2007-05-15 First public release.