using System;
using System.Collections;
namespace Iesi.Collections{
/// <summary>
/// <p>A collection that contains no duplicate elements. This interface models the mathematical
/// <c>Set</c> abstraction.
/// The order of elements in a set is dependant on (a)the data-structure implementation, and
/// (b)the implementation of the various <c>Set</c> methods, and thus is not guaranteed.</p>
///
/// <p>None of the <c>Set</c> implementations in this library are guranteed to be thread-safe
/// in any way unless wrapped in a <c>SynchronizedSet</c>.</p>
///
/// <p>The following table summarizes the binary operators that are supported by the <c>Set</c> class.</p>
/// <list type="table">
/// <listheader>
/// <term>Operation</term>
/// <term>Description</term>
/// <term>Method</term>
/// </listheader>
/// <item>
/// <term>Union (OR)</term>
/// <term>Element included in result if it exists in either <c>A</c> OR <c>B</c>.</term>
/// <term><c>Union()</c></term>
/// </item>
/// <item>
/// <term>Intersection (AND)</term>
/// <term>Element included in result if it exists in both <c>A</c> AND <c>B</c>.</term>
/// <term><c>InterSect()</c></term>
/// </item>
/// <item>
/// <term>Exclusive Or (XOR)</term>
/// <term>Element included in result if it exists in one, but not both, of <c>A</c> and <c>B</c>.</term>
/// <term><c>ExclusiveOr()</c></term>
/// </item>
/// <item>
/// <term>Minus (n/a)</term>
/// <term>Take all the elements in <c>A</c>. Now, if any of them exist in <c>B</c>, remove
/// them. Note that unlike the other operators, <c>A - B</c> is not the same as <c>B - A</c>.</term>
/// <term><c>Minus()</c></term>
/// </item>
/// </list>
/// </summary>
public interface ISet : ICollection, ICloneable
{
/// <summary>
/// Performs a "union" of the two sets, where all the elements
/// in both sets are present. That is, the element is included if it is in either <c>a</c> or <c>b</c>.
/// Neither this set nor the input set are modified during the operation. The return value
/// is a <c>Clone()</c> of this set with the extra elements added in.
/// </summary>
/// <param name="a">A collection of elements.</param>
/// <returns>A new <c>Set</c> containing the union of this <c>Set</c> with the specified collection.
/// Neither of the input objects is modified by the union.</returns>
ISet Union(ISet a);
/// <summary>
/// Performs an "intersection" of the two sets, where only the elements
/// that are present in both sets remain. That is, the element is included if it exists in
/// both sets. The <c>Intersect()</c> operation does not modify the input sets. It returns
/// a <c>Clone()</c> of this set with the appropriate elements removed.
/// </summary>
/// <param name="a">A set of elements.</param>
/// <returns>The intersection of this set with <c>a</c>.</returns>
ISet Intersect(ISet a);
/// <summary>
/// Performs a "minus" of set <c>b</c> from set <c>a</c>. This returns a set of all
/// the elements in set <c>a</c>, removing the elements that are also in set <c>b</c>.
/// The original sets are not modified during this operation. The result set is a <c>Clone()</c>
/// of this <c>Set</c> containing the elements from the operation.
/// </summary>
/// <param name="a">A set of elements.</param>
/// <returns>A set containing the elements from this set with the elements in <c>a</c> removed.</returns>
ISet Minus(ISet a);
/// <summary>
/// Performs an "exclusive-or" of the two sets, keeping only the elements that
/// are in one of the sets, but not in both. The original sets are not modified
/// during this operation. The result set is a <c>Clone()</c> of this set containing
/// the elements from the exclusive-or operation.
/// </summary>
/// <param name="a">A set of elements.</param>
/// <returns>A set containing the result of <c>a ^ b</c>.</returns>
ISet ExclusiveOr(ISet a);
/// <summary>
/// Returns <see langword="true" /> if this set contains the specified element.
/// </summary>
/// <param name="o">The element to look for.</param>
/// <returns><see langword="true" /> if this set contains the specified element, <see langword="false" /> otherwise.</returns>
bool Contains(object o);
/// <summary>
/// Returns <see langword="true" /> if the set contains all the elements in the specified collection.
/// </summary>
/// <param name="c">A collection of objects.</param>
/// <returns><see langword="true" /> if the set contains all the elements in the specified collection, <see langword="false" /> otherwise.</returns>
bool ContainsAll(ICollection c);
/// <summary>
/// Returns <see langword="true" /> if this set contains no elements.
/// </summary>
bool IsEmpty { get; }
/// <summary>
/// Adds the specified element to this set if it is not already present.
/// </summary>
/// <param name="o">The object to add to the set.</param>
/// <returns><see langword="true" /> is the object was added, <see langword="false" /> if it was already present.</returns>
bool Add(object o);
/// <summary>
/// Adds all the elements in the specified collection to the set if they are not already present.
/// </summary>
/// <param name="c">A collection of objects to add to the set.</param>
/// <returns><see langword="true" /> is the set changed as a result of this operation, <see langword="false" /> if not.</returns>
bool AddAll(ICollection c);
/// <summary>
/// Removes the specified element from the set.
/// </summary>
/// <param name="o">The element to be removed.</param>
/// <returns><see langword="true" /> if the set contained the specified element, <see langword="false" /> otherwise.</returns>
bool Remove(object o);
/// <summary>
/// Remove all the specified elements from this set, if they exist in this set.
/// </summary>
/// <param name="c">A collection of elements to remove.</param>
/// <returns><see langword="true" /> if the set was modified as a result of this operation.</returns>
bool RemoveAll(ICollection c);
/// <summary>
/// Retains only the elements in this set that are contained in the specified collection.
/// </summary>
/// <param name="c">Collection that defines the set of elements to be retained.</param>
/// <returns><see langword="true" /> if this set changed as a result of this operation.</returns>
bool RetainAll(ICollection c);
/// <summary>
/// Removes all objects from the set.
/// </summary>
void Clear();
}
}
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