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. */
public String toString()
{
return name();
}
/*-----------------------------------------------------------*/
}
