Name: skT88420 Date: 07/22/99


Use JavaCC 1.1 (from metamata.com) to convert the file below.
Then use javac-ea to compile.

It crashes with NullPointerException and the request to submit a bug report.

The program as such compiles ok, e.g., with JDK 1.2.2 javac.

// based on examples by Chuck McManis
// recognize arithmetic expressions

PARSER_BEGIN(Calc0) // must define parser class
  public class Calc0 {
    public static void main (String args []) {
      Calc0 parser = new Calc0(System.in);
      for (;;)
try {
if (parser.expr() == -1)
System.exit(0);
} catch (Exception e) {
e.printStackTrace(); System.exit(1);
}
    }
  }
PARSER_END(Calc0)

SKIP: // defines input to be ignored
  { " " | "\r" | "\t"
  }

TOKEN: // defines token names
  { < EOL: "\n" >
  | < CONSTANT: ( <DIGIT> )+ > // re: 1 or more
  | < #DIGIT: ["0" - "9"] > // private re
  }

int expr(): // expr: sum \n
  {} // -1 at eof, 0 at eol
  { sum() <EOL> { return 1; }
  | <EOL> { return 0; }
  | <EOF> { return -1; }
  }

void sum(): // sum: product { +- product }
  {}
  { product() ( ( "+" | "-" ) product() )*
  }

void product(): // product: term { *%/ term }
  {}
  { term() ( ( "*" | "%" | "/" ) term() )*
  }

void term(): // term: +term | -term | (sum) | number
  {}
  { "+" term()
  | "-" term()
  | "(" sum() ")"
  | <CONSTANT>
  }
(Review ID: 88251)
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