+++ /dev/null
-
-package java_cup;
-
-import java.util.Hashtable;
-import java.util.Enumeration;
-
-/** This class represents a set of symbols and provides a series of
- * set operations to manipulate them.
- *
- * @see java_cup.symbol
- * @version last updated: 11/25/95
- * @author Scott Hudson
- */
-public class symbol_set {
-
- /*-----------------------------------------------------------*/
- /*--- Constructor(s) ----------------------------------------*/
- /*-----------------------------------------------------------*/
-
- /** Constructor for an empty set. */
- public symbol_set() { }
-
- /** Constructor for cloning from another set.
- * @param other the set we are cloning from.
- */
- public symbol_set(symbol_set other) throws internal_error
- {
- not_null(other);
- _all = (Hashtable)other._all.clone();
- }
-
- /*-----------------------------------------------------------*/
- /*--- (Access to) Instance Variables ------------------------*/
- /*-----------------------------------------------------------*/
-
- /** A hash table to hold the set. Symbols are keyed using their name string.
- */
- protected Hashtable _all = new Hashtable(11);
-
- /** Access to all elements of the set. */
- public Enumeration all() {return _all.elements();}
-
- /** size of the set */
- public int size() {return _all.size();}
-
- /*-----------------------------------------------------------*/
- /*--- (Access to) Instance Variables ------------------------*/
- /*-----------------------------------------------------------*/
-
- /** Helper function to test for a null object and throw an exception
- * if one is found.
- * @param obj the object we are testing.
- */
- protected void not_null(Object obj) throws internal_error
- {
- if (obj == null)
- throw new internal_error("Null object used in set operation");
- }
-
- /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
-
- /** Determine if the set contains a particular symbol.
- * @param sym the symbol we are looking for.
- */
- public boolean contains(symbol sym) {return _all.containsKey(sym.name());}
-
- /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
-
- /** Determine if this set is an (improper) subset of another.
- * @param other the set we are testing against.
- */
- public boolean is_subset_of(symbol_set other) throws internal_error
- {
- not_null(other);
-
- /* walk down our set and make sure every element is in the other */
- for (Enumeration e = all(); e.hasMoreElements(); )
- if (!other.contains((symbol)e.nextElement()))
- return false;
-
- /* they were all there */
- return true;
- }
-
- /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
-
- /** Determine if this set is an (improper) superset of another.
- * @param other the set we are are testing against.
- */
- public boolean is_superset_of(symbol_set other) throws internal_error
- {
- not_null(other);
- return other.is_subset_of(this);
- }
-
- /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
-
- /** Add a single symbol to the set.
- * @param sym the symbol we are adding.
- * @return true if this changes the set.
- */
- public boolean add(symbol sym) throws internal_error
- {
- Object previous;
-
- not_null(sym);
-
- /* put the object in */
- previous = _all.put(sym.name(),sym);
-
- /* if we had a previous, this is no change */
- return previous == null;
- }
-
- /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
-
- /** Remove a single symbol if it is in the set.
- * @param sym the symbol we are removing.
- */
- public void remove(symbol sym) throws internal_error
- {
- not_null(sym);
- _all.remove(sym.name());
- }
-
- /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
-
- /** Add (union) in a complete set.
- * @param other the set we are adding in.
- * @return true if this changes the set.
- */
- public boolean add(symbol_set other) throws internal_error
- {
- boolean result = false;
-
- not_null(other);
-
- /* walk down the other set and do the adds individually */
- for (Enumeration e = other.all(); e.hasMoreElements(); )
- result = add((symbol)e.nextElement()) || result;
-
- return result;
- }
-
- /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
-
- /** Remove (set subtract) a complete set.
- * @param other the set we are removing.
- */
- public void remove(symbol_set other) throws internal_error
- {
- not_null(other);
-
- /* walk down the other set and do the removes individually */
- for (Enumeration e = other.all(); e.hasMoreElements(); )
- remove((symbol)e.nextElement());
- }
-
- /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
-
- /** Equality comparison. */
- public boolean equals(symbol_set other)
- {
- if (other == null || other.size() != size()) return false;
-
- /* once we know they are the same size, then improper subset does test */
- try {
- return is_subset_of(other);
- } catch (internal_error e) {
- /* can't throw the error (because super class doesn't), so we crash */
- e.crash();
- return false;
- }
- }
-
- /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
-
- /** Generic equality comparison. */
- public boolean equals(Object other)
- {
- if (!(other instanceof symbol_set))
- return false;
- else
- return equals((symbol_set)other);
- }
-
- /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
-
- /** Compute a hash code. */
- public int hashCode()
- {
- int result = 0;
- int cnt;
- Enumeration e;
-
- /* hash together codes from at most first 5 elements */
- for (e = all(), cnt=0 ; e.hasMoreElements() && cnt<5; cnt++)
- result ^= ((symbol)e.nextElement()).hashCode();
-
- return result;
- }
-
- /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
-
- /** Convert to a string. */
- public String toString()
- {
- String result;
- boolean comma_flag;
-
- result = "{";
- comma_flag = false;
- for (Enumeration e = all(); e.hasMoreElements(); )
- {
- if (comma_flag)
- result += ", ";
- else
- comma_flag = true;
-
- result += ((symbol)e.nextElement()).name();
- }
- result += "}";
-
- return result;
- }
-
- /*-----------------------------------------------------------*/
-
-}
-
-
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