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From: Robert Jacobson <rljacobson@gmail.com>
Newsgroups: comp.compilers
Subject: Re: Grammar with low-precedence postfix operator?
Date: Sat, 21 Feb 2015 12:55:52 -0800 (PST)
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Xref: csiph.com comp.compilers:1534

Thank you everyone for your help. The solution I found for solving my language
ambiguity uses ANTLR's semantic predicates feature which can turn off
production alternatives at parse time. I use a predicate (below) to suppress
implicit multiplication in the presence of a binary plus operator.

expr
	:	LEAF
	|	LPAREN expr RPAREN	//parentheses
	|	<assoc=right> expr POWER expr
	|	(PLUS | MINUS) expr //unary plus/minus
	|	expr { _input.LT(1).getType() != PLUS &&  _input.LT(1).getType() != MINUS}?
expr //implicit multiplication
	|	expr (DIV | MUL) expr //division and explicit multiplication
	|	expr (PLUS | MINUS) expr //addition/subtraction
	|	expr '&' //postfix parenthesization.
	;

Best regards,

Robert