package java_cup;
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/** This abstract class serves as the base class for grammar symbols (i.e.,
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* both terminals and non-terminals). Each symbol has a name string, and
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* a string giving the type of object that the symbol will be represented by
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* on the runtime parse stack. In addition, each symbol maintains a use count
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* in order to detect symbols that are declared but never used, and an index
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* number that indicates where it appears in parse tables (index numbers are
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* unique within terminals or non terminals, but not across both).
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*
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* @see java_cup.terminal
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* @see java_cup.non_terminal
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* @version last updated: 11/25/95
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* @author Scott Hudson
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*/
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public abstract class symbol {
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/*-----------------------------------------------------------*/
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/*--- Constructor(s) ----------------------------------------*/
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/*-----------------------------------------------------------*/
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/** Full constructor.
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* @param nm the name of the symbol.
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* @param tp a string with the type name.
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*/
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public symbol(String nm, String tp)
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{
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/* sanity check */
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if (nm == null) nm = "";
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/* apply default if no type given */
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if (tp == null) tp = "java_cup.runtime.token";
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_name = nm;
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_stack_type = tp;
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}
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/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
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/** Constructor with default type.
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* @param nm the name of the symbol.
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*/
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public symbol(String nm)
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{
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this(nm, null);
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}
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/*-----------------------------------------------------------*/
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/*--- (Access to) Instance Variables ------------------------*/
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/*-----------------------------------------------------------*/
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/** String for the human readable name of the symbol. */
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protected String _name;
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/** String for the human readable name of the symbol. */
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public String name() {return _name;}
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/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
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/** String for the type of object used for the symbol on the parse stack. */
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protected String _stack_type;
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/** String for the type of object used for the symbol on the parse stack. */
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public String stack_type() {return _stack_type;}
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/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
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/** Count of how many times the symbol appears in productions. */
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protected int _use_count = 0;
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/** Count of how many times the symbol appears in productions. */
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public int use_count() {return _use_count;}
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/** Increment the use count. */
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public void note_use() {_use_count++;}
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/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
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/** Index of this symbol (terminal or non terminal) in the parse tables.
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* Note: indexes are unique among terminals and unique among non terminals,
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* however, a terminal may have the same index as a non-terminal, etc.
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*/
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protected int _index;
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/** Index of this symbol (terminal or non terminal) in the parse tables.
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* Note: indexes are unique among terminals and unique among non terminals,
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* however, a terminal may have the same index as a non-terminal, etc.
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*/
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public int index() {return _index;}
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/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
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/** Indicate if this is a non-terminal. Here in the base class we
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* don't know, so this is abstract.
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*/
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public abstract boolean is_non_term();
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/*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
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/** Convert to a string. */
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public String toString()
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{
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return name();
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}
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/*-----------------------------------------------------------*/
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};
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