[antlr-interest] Building an AST Tree?

Setia, Namit namit.setia at lehman.com
Thu Jul 24 13:57:04 PDT 2008


Thanks for the help.

Does anyone know of any good tutorials/examples on how to build an AST
with c#?  When I get the top level tree, it's children are the
individual characters of the string I passed in.  I'm not quite sure
what the approach should be to get it to parse into an AST (Maybe my
understanding is wrong, but I'm trying to get a tree like what you see
in the antlrworks interpreter).

I've been trying to find some good examples for the latest version of
antlr, but none of the csharp samples I could find work.

Antlr.Runtime.ICharStream str = new
Antlr.Runtime.ANTLRStringStream("ap=function(\"hello\",4,5);");
qss_grammarLexer qlex = new qss_grammarLexer(str);
Antlr.Runtime.CommonTokenStream tokens = new
Antlr.Runtime.CommonTokenStream(qlex);
qss_grammarParser grammar = new qss_grammarParser(tokens);
qss_grammarParser.qexprlist_return ret = grammar.qexprlist();
CommonTree t = (CommonTree)ret.Tree;

--> t.Children is an array  of tokens [ {a},{p},{=},{f},{u},{n}....]  

------------------------------------------------------------------------
---

grammar qss_grammar;

options
{
	language=CSharp2;
	output=AST;
}

qexprlist
  : ( qassignment_statement )* EOF
  ;

qassignment_statement
  : qassignment SEMI { Console.Write("hello"); }
  ;

qassignment
  : (qname ASSIGN )? qexpr
  ;

qprimary_expr
  : qint
  | qvname
  | (LPAREN qexpr RPAREN ) 
  | qfunction
  | qarray
  | qstring
  ;

qsign_expr
  : qprimary_expr
  ;

qmul_expr
  : qsign_expr (( MUL | DIV | MOD ) qsign_expr)*
  ;
  
qexpr
  	:	 qmul_expr (( PLUS | MINUS ) qmul_expr)*
  ;



PLUS	:	'+';
MINUS	:	'-';
DIV	:	'/';
MUL	:	'*';
MOD	:	'%';
POW	:	'^';
LETTER	:	'a'..'z'|'A'..'Z';
DIGIT	:	'0'..'9';
PER	:	'.';
SEMI	:	';';
ASSIGN	:	'=';
EQ	:	'=''=';
NQ	:	'!''=';
LEQ	:	'<''=';
GEQ	:	'>''=';
LPAREN	:	'(';
RPAREN	:	')';

qint	:	(DIGIT)*;
qname	:	LETTER(LETTER|DIGIT)*;
qstr	:	(LETTER|DIGIT)*;
qstring	:	'"' (LETTER|DIGIT)* '"';
qinputval:	(LETTER|DIGIT)*;
qvname	:	(LETTER(LETTER|DIGIT)*)(':'qinputval('.'qinputval)*)?;
qarray	:	'{' (qstring|qvname)(','(qstring|qvname))* '}';
qfunction:	(LETTER(LETTER|DIGIT)*)'('
qprimary_expr(','qprimary_expr)* ')';


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