Line Number Information in BYacc/J

In order to know until which line parsing has been done, we can utilize %line directive in JFlex specification and add relevant methods.

%byaccj

%line

%column

%{

  private Parser yyparser;

  public Yylex (java.io.Reader r, Parser yyparser) {

    this (r);

    this.yyparser = yyparser;

  }

  int getLineNum () {

    return (yyline+1);

  }

  int getColNum () {

    return (yycolumn+1);

  }

%}

"yyline+1" expression is needed because JFlex starts counting from 0.

To get the position information in BYacc/J, add several lines in the specification:

private Yylex lexer;

public void yyerror (String strError) {

  System.err.println ("Error at line: " + lexer.getLineNum() + ": " + strError);

}