ANTLR

ANTLR is an open source grammar language created in 1992.

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In computer-based language recognition, ANTLR (pronounced Antler), or Another Tool For Language Recognition, is a parser generator that uses LL(*) for parsing. ANTLR is the successor to the Purdue Compiler Construction Tool Set (PCCTS), first developed in 1989, and is under active development. Its maintainer is Professor Terence Parr of the University of San Francisco.. Read more on Wikipedia...

ANTLR website
ANTLR Wikipedia page
PLDB has 3 documentation sites for ANTLR: www.antlr.org, www.antlr2.org, theantlrguy.atlassian.net
There are at least 1,415 ANTLR repos on GitHub
ANTLR first developed in University of San Francisco
PLDB estimates there are currently 30 job openings for ANTLR programmers.
file extensions for ANTLR include g4
ANTLR on Twitter
The Google BigQuery Public Dataset GitHub snapshot shows 3k users using ANTLR in 3k repos on GitHub
Explore ANTLR snippets on Rosetta Code
ANTLR on HOPL
ANTLR grammar for ANTLR
Pygments supports syntax highlighting for ANTLR
GitHub supports syntax highlighting for ANTLR
Indeed.com has 7 matches for "antlr engineer".
antlr.org was registered in 1997
See also: (18 related languages)Java, ActionScript, C, C#, JavaScript, Objective-C, Perl, Python, Ruby, Standard ML, Swift, Go, Groovy, Jython, Processing, Coco/R, JavaCC, PEG

Example from the web:

/** Taken from "The Definitive ANTLR 4 Reference" by Terence Parr */
// Derived from http://json.org
grammar JSON;
json
   : value
   ;
obj
   : '{' pair (',' pair)* '}'
   | '{' '}'
   ;
pair
   : STRING ':' value
   ;
arr
   : '[' value (',' value)* ']'
   | '[' ']'
   ;
value
   : STRING
   | NUMBER
   | obj
   | arr
   | 'true'
   | 'false'
   | 'null'
   ;

STRING
   : '"' (ESC | SAFECODEPOINT)* '"'
   ;

fragment ESC
   : '\\' (["\\/bfnrt] | UNICODE)
   ;
fragment UNICODE
   : 'u' HEX HEX HEX HEX
   ;
fragment HEX
   : [0-9a-fA-F]
   ;
fragment SAFECODEPOINT
   : ~ ["\\\u0000-\u001F]
   ;

NUMBER
   : '-'? INT ('.' [0-9] +)? EXP?
   ;

fragment INT
   : '0' | [1-9] [0-9]*
   ;

// no leading zeros

fragment EXP
   : [Ee] [+\-]? INT
   ;

// \- since - means "range" inside [...]

WS
   : [ \t\n\r] + -> skip
   ;

Example from Wikipedia:

TextReader reader;
 // (...) Fill TextReader with character
 SumLexer lexer = new SumLexer(reader);
 SumParser parser = new SumParser(lexer);

 parser.expression();

Feature	Supported	Token	Example
Booleans	✓	true false
MultiLine Comments	✓	/* */	/* A comment */
Comments	✓		// A comment
Line Comments	✓	//	// A comment
Semantic Indentation	X

ANTLR - Grammar language

Language features