grammar simpleCalc;

options {
    output = AST;
}

tokens {
	PLUS 	= '+' ;
	MINUS	= '-' ;
	MULT	= '*' ;
	DIV	= '/' ;
	LPAREN  = '(';
	RPAREN  = ')';
	EQUAL   = '='; 
 }
 
@parser::header {
		  package net.certiv.x.outputs; 
		}

@lexer::header {
		  package net.certiv.x.outputs;
		}

assign	: lvalue EQUAL^ expr EOF;

lvalue	: IDENT ;

expr	: term ( ( PLUS^ | MINUS^ ) term )* ;

term	: operand ( ( MULT^ | DIV^ ) operand )* ;

operands : operand+ ;

operand : ident
		| digits
		| LPAREN! expr RPAREN!		
		;

ident  : i=IDENT { System.out.println("IDENT: " + $i.toString()); };

digits : DIGITS ;

IDENT : LETTER (LETTER | DIGIT)* ;

DIGITS : a+=DIGIT+ { System.out.println("DIGITS: " + $a.toString()); } ;

WS	: ( '\t' | ' ' | '\r' | '\n'| '\u000C' )+ { $channel = HIDDEN; } ;

fragment LETTER : UPPER | LOWER ;

fragment DIGIT : '0'..'9';

fragment LOWER : 'a'..'z';

fragment UPPER : 'A'..'Z';