ANTLR v3 is an improved version of ANTLR that provides more robust grammars, error recovery, attributes, tree construction and code generation capabilities compared to version 2. Some key features include single element EBNF grammar syntax, support for parameters and return values in rules, dynamic scoping of attributes, automatic and rewrite-based tree construction, tree grammars, and internationalization through string templates. The runtime is also better organized and separated into modules for parsing, trees, and debugging.

1. ANTLR v3 Overview (for ANTLR v2 users) Terence Parr University of San Francisco

3. Block Info Flow Diagram

4. Grammar Syntax header {…} /** doc comment */ kind grammar name ; options {…} tokens {…} scopes… action rules … /** doc comment */ rule[String s, int z] returns [int x, int y] throws E options {…} scopes init {…} :  |  ; exceptions ^(root child1 … childN) Trees Note: No inheritance

6. Example Grammar grammar SimpleParser; program : variable* method+ ; variable: "int" ID (‘=‘ expr)? ';’ ; method : "method" ID '(' ')' '{' variable* statement+ '}' ; statement : ID ‘=‘ expr ';' | "return" expr ';' ; expr : ID | INT ; ID : ('a'..'z'|'A'..'Z')+ ; INT : '0'..'9'+ ; WS : (' '|''|'')+ {channel=99;} ;

7. Using the parser CharStream in = new ANTLRFileStream(“inputfile”); SimpleParserLexer lexer = new SimpleParserLexer(in); CommonTokenStream tokens = new CommonTokenStream(lexer); SimpleParser p = new SimpleParser(tokens); p.program(); // invoke start rule

9. Recursion Warnings a : a A | B ; t.g:2:5: Alternative 1 discovers infinite left-recursion to a from a t.g:2:5: Alternative 1: after matching input such as B decision cannot predict what comes next due to recursion overflow to c from b // with -Im 0 (secret internal parameter) a : b | B ; b : c ; c : B b ;

13. Example Error Recovery int i = 0; method foo( { int j = i; i = 4 } [program, method]: line 2:12 mismatched token: [@14,23:23='{',<14>,2:12]; expecting type ')' [program, method, statement]: line 5:0 mismatched token: [@31,46:46='}',<15>,5:0]; expecting type ';' int i = 0; method foo() ) { int j = i; i = = 4; } [program, method]: line 2:13 mismatched token: [@15,24:24=')',<13>,2:13]; expecting type '{' [program, method, statement, expr]: line 4:6 mismatched token: [@32,47:47='=',<6>,4:6]; expecting set null Note: I put in two errors each so you’ll see it continues properly One token insertion One token deletion

29. Sample code gen templates /** Dump the elements one per line and stick in debugging * location() trigger in front. */ element() ::= << <if(debug)> dbg.location(<it.line>,<it.pos>);<> <endif> <it.el><> >> /** match a token optionally with a label in front */ tokenRef(token,label,elementIndex) ::= << <if(label)> <label>=input.LT(1);<> <endif> match(input,<token>,FOLLOW_<token>_in_<ruleName><elementIndex>); >>