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Diffstat (limited to 'src/syntaxParser/java_cup/terminal_set.java')
| -rw-r--r-- | src/syntaxParser/java_cup/terminal_set.java | 253 |
1 files changed, 253 insertions, 0 deletions
diff --git a/src/syntaxParser/java_cup/terminal_set.java b/src/syntaxParser/java_cup/terminal_set.java new file mode 100644 index 0000000..e921cb5 --- /dev/null +++ b/src/syntaxParser/java_cup/terminal_set.java @@ -0,0 +1,253 @@ + +package java_cup; + +import java.util.BitSet; + +/** A set of terminals implemented as a bitset. + * @version last updated: 11/25/95 + * @author Scott Hudson + */ +public class terminal_set { + + /*-----------------------------------------------------------*/ + /*--- Constructor(s) ----------------------------------------*/ + /*-----------------------------------------------------------*/ + + /** Constructor for an empty set. */ + public terminal_set() + { + /* allocate the bitset at what is probably the right size */ + _elements = new BitSet(terminal.number()); + } + + /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/ + + /** Constructor for cloning from another set. + * @param other the set we are cloning from. + */ + public terminal_set(terminal_set other) + throws internal_error + { + not_null(other); + _elements = (BitSet)other._elements.clone(); + } + + /*-----------------------------------------------------------*/ + /*--- (Access to) Static (Class) Variables ------------------*/ + /*-----------------------------------------------------------*/ + + /** Constant for the empty set. */ + public static final terminal_set EMPTY = new terminal_set(); + + /*-----------------------------------------------------------*/ + /*--- (Access to) Instance Variables ------------------------*/ + /*-----------------------------------------------------------*/ + + /** Bitset to implement the actual set. */ + protected BitSet _elements; + + /*-----------------------------------------------------------*/ + /*--- General Methods ----------------------------------------*/ + /*-----------------------------------------------------------*/ + + /** 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 is empty. */ + public boolean empty() + { + return equals(EMPTY); + } + + /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/ + + /** Determine if the set contains a particular terminal. + * @param sym the terminal symbol we are looking for. + */ + public boolean contains(terminal sym) + throws internal_error + { + not_null(sym); + return _elements.get(sym.index()); + } + + /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/ + + /** Given its index determine if the set contains a particular terminal. + * @param indx the index of the terminal in question. + */ + public boolean contains(int indx) + { + return _elements.get(indx); + } + + /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/ + + /** Determine if this set is an (improper) subset of another. + * @param other the set we are testing against. + */ + public boolean is_subset_of(terminal_set other) + throws internal_error + { + not_null(other); + + /* make a copy of the other set */ + BitSet copy_other = (BitSet)other._elements.clone(); + + /* and or in */ + copy_other.or(_elements); + + /* if it hasn't changed, we were a subset */ + return copy_other.equals(other._elements); + } + + /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/ + + /** Determine if this set is an (improper) superset of another. + * @param other the set we are testing against. + */ + public boolean is_superset_of(terminal_set other) + throws internal_error + { + not_null(other); + return other.is_subset_of(this); + } + + /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/ + + /** Add a single terminal to the set. + * @param sym the terminal being added. + * @return true if this changes the set. + */ + public boolean add(terminal sym) + throws internal_error + { + boolean result; + + not_null(sym); + + /* see if we already have this */ + result = _elements.get(sym.index()); + + /* if not we add it */ + if (!result) + _elements.set(sym.index()); + + return result; + } + + /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/ + + /** Remove a terminal if it is in the set. + * @param sym the terminal being removed. + */ + public void remove(terminal sym) + throws internal_error + { + not_null(sym); + _elements.clear(sym.index()); + } + + /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/ + + /** Add (union) in a complete set. + * @param other the set being added. + * @return true if this changes the set. + */ + public boolean add(terminal_set other) + throws internal_error + { + not_null(other); + + /* make a copy */ + BitSet copy = (BitSet)_elements.clone(); + + /* or in the other set */ + _elements.or(other._elements); + + /* changed if we are not the same as the copy */ + return !_elements.equals(copy); + } + + /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/ + + /** Determine if this set intersects another. + * @param other the other set in question. + */ + public boolean intersects(terminal_set other) + throws internal_error + { + not_null(other); + + /* make a copy of the other set */ + BitSet copy = (BitSet)other._elements.clone(); + + /* xor out our values */ + copy.xor(this._elements); + + /* see if its different */ + return !copy.equals(other._elements); + } + + /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/ + + /** Equality comparison. */ + public boolean equals(terminal_set other) + { + if (other == null) + return false; + else + return _elements.equals(other._elements); + } + + /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/ + + /** Generic equality comparison. */ + public boolean equals(Object other) + { + if (!(other instanceof terminal_set)) + return false; + else + return equals((terminal_set)other); + } + + /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/ + + /** Convert to string. */ + public String toString() + { + String result; + boolean comma_flag; + + result = "{"; + comma_flag = false; + for (int t = 0; t < terminal.number(); t++) + { + if (_elements.get(t)) + { + if (comma_flag) + result += ", "; + else + comma_flag = true; + + result += terminal.find(t).name(); + } + } + result += "}"; + + return result; + } + + /*-----------------------------------------------------------*/ + +} + |