package java_cup;

/** This abstract class serves as the base class for grammar symbols (i.e.,
 * both terminals and non-terminals).  Each symbol has a name string, and
 * a string giving the type of object that the symbol will be represented by
 * on the runtime parse stack.  In addition, each symbol maintains a use count
 * in order to detect symbols that are declared but never used, and an index
 * number that indicates where it appears in parse tables (index numbers are
 * unique within terminals or non terminals, but not across both).
 *
 * @see     java_cup.terminal
 * @see     java_cup.non_terminal
 * @version last updated: 7/3/96
 * @author  Frank Flannery
 */
public abstract class symbol {
    /*-----------------------------------------------------------*/
    /*--- Constructor(s) ----------------------------------------*/
    /*-----------------------------------------------------------*/

    /** Full constructor.
     * @param nm the name of the symbol.
     * @param tp a string with the type name.
     */
    public symbol(String nm, String tp) {
        /* sanity check */
        if (nm == null) nm = "";

        /* apply default if no type given */
        if (tp == null) tp = "Object";

        _name = nm;
        _stack_type = tp;
    }

    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /** Constructor with default type. 
     * @param nm the name of the symbol.
     */
    public symbol(String nm) {
        this(nm, null);
    }

    /*-----------------------------------------------------------*/
    /*--- (Access to) Instance Variables ------------------------*/
    /*-----------------------------------------------------------*/

    /** String for the human readable name of the symbol. */
    protected String _name;

    /** String for the human readable name of the symbol. */
    public String name() {
        return _name;
    }

    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /** String for the type of object used for the symbol on the parse stack. */
    protected String _stack_type;

    /** String for the type of object used for the symbol on the parse stack. */
    public String stack_type() {
        return _stack_type;
    }

    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /** Count of how many times the symbol appears in productions. */
    protected int _use_count = 0;

    /** Count of how many times the symbol appears in productions. */
    public int use_count() {
        return _use_count;
    }

    /** Increment the use count. */
    public void note_use() {
        _use_count++;
    }

    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /** Index of this symbol (terminal or non terminal) in the parse tables.
     *  Note: indexes are unique among terminals and unique among non terminals,
     *  however, a terminal may have the same index as a non-terminal, etc. 
     */
    protected int _index;

    /** Index of this symbol (terminal or non terminal) in the parse tables.
     *  Note: indexes are unique among terminals and unique among non terminals,
     *  however, a terminal may have the same index as a non-terminal, etc. 
     */
    public int index() {
        return _index;
    }

    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /** Indicate if this is a non-terminal.  Here in the base class we
     *  don't know, so this is abstract.  
     */
    public abstract boolean is_non_term();

    /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/

    /** Convert to a string. */
    @Override
    public String toString() {
        return name();
    }

    /*-----------------------------------------------------------*/

}
