[antlr-interest] Priority in interpreting input

Peter Götz peter.goetz at gutefrage.net
Tue Oct 23 04:10:34 PDT 2012

Hi there, 

I am using ANTLR to parse an arithmetic expression and create an abstract syntax tree from it with node objects for every node type. A typical expression looks like this: 

    2 * sqrt(a1 + b2)

As you can see, those expressions can contain literal number values, functions and variables. In the crucial part of my grammar I have the following: 

    factor: LITERAL | funct | METRIC;

And as the definition of LITERAL and METRIC this: 

    METRIC : (Letter|Digit|Separator)+;
    LITERAL : '0'..'9';

This is a very much simplified version of my real definitions just to make my point. If now I want to parse an expression it seems that ANTLR is not able to recognize the LITERAL, since this is matching as a METRIC, too. 

How do I tell ANTLR that a literal-recognition has precedence over a recognized metric? 

Thanks a lot for your help!

Best regards, 


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