Question

So I’m trying to write a parser in ANTLR, this is my first time using it and I’m running into a problem that I can’t find a solution for, apologies if this is a very simple problem. Anyway, the error I’m getting is:

"(100): Expr.g:1:13:syntax error: antlr: MismatchedTokenException(74!=52)"

The code I’m currently using is:

grammar Expr.g;

options{
output=AST;
}


tokens{
    MAIN = 'main';
    OPENBRACKET = '(';
    CLOSEBRACKET = ')';
    OPENCURLYBRACKET = '{';
    CLOSECURLYBRACKET = '}';
    COMMA = ',';
    SEMICOLON = ';';
    GREATERTHAN = '>';
    LESSTHAN = '<';
    GREATEROREQUALTHAN = '>=';
        LESSTHANOREQUALTHAN = '<=';
    NOTEQUAL = '!=';
    ISEQUALTO = '==';
    WHILE = 'while';
    IF = 'if';
    ELSE = 'else';
    READ = 'read';
    OUTPUT = 'output';
    PRINT = 'print';
    RETURN = 'return';
    READC = 'readc';
    OUTPUTC = 'outputc';
    PLUS = '+';
    MINUS = '-';
    DIVIDE = '/';
    MULTIPLY = '*';
    PERCENTAGE = '%';
}


@header {
//package test;
import java.util.HashMap;
}

@lexer::header {
//package test;
}

@members {
/** Map variable name to Integer object holding value */
HashMap memory = new HashMap();
}

prog:   stat+ ;

stat:   expr NEWLINE {System.out.println($expr.value);}
    |   ID '=' expr NEWLINE
        {memory.put($ID.text, new Integer($expr.value));}
    |   NEWLINE
    ;

expr returns [int value]
    :   e=multExpr {$value = $e.value;}
        (   '+' e=multExpr {$value += $e.value;}
        |   '-' e=multExpr {$value -= $e.value;}
        )*
    ;

multExpr returns [int value]
    :   e=atom {$value = $e.value;} ('*' e=atom {$value *= $e.value;})*
    ; 

atom returns [int value]
    :   INT {$value = Integer.parseInt($INT.text);}
    |   ID
        {
        Integer v = (Integer)memory.get($ID.text);
        if ( v!=null ) $value = v.intValue();
        else System.err.println("undefined variable "+$ID.text);
        }
    |   '(' e=expr ')' {$value = $e.value;}
    ;

IDENT  :   ('a'..'z'^|'A'..'Z'^)+ ; :   .;
INT :   '0'..'9'+ ;
NEWLINE:'\r'? '\n' ;
WS  :   (' '|'\t')+ {skip();} ;

Thanks for any help.

EDIT: Well, I’m an idiot, it’s just a formatting error. Thanks for the responses from those who helped out.

Answer 1

You have some illegal characters after your IDENT token:

IDENT  :   ('a'..'z'^|'A'..'Z'^)+ ; :   .;

The : .; are invalid there. And you’re also trying to mix the tree-rewrite operator ^ inside a lexer rule, which is illegal: remove them. Lastly, you’ve named it IDENT while in your parser rules, you’re using ID.

It should be:

ID : ('a'..'z' | 'A'..'Z')+ ;