April
9th,
2008
Previously we discussed the opposite problem. This is a lesser but often more frustrating problem because there is no, AFAIK, built in solution for the BCL. However it’s problem that can be solved once and reused with a generic solution. IComparable
To work around this we’ll create a new class that can wrap both a value and an instance of IComparable(Of T). Lets call it ComparerNode
Unfortunately generic classes will not provide a 1:1 mapping. However getting to the actual data is strongly typed and comes through a simple property.
public sealed class ComparerNode<T> : IComparable<ComparerNode<T>> {
private readonly IComparer<T> m_comparer;
private readonly T m_value;
public IComparer<T> Comparer {
get { return m_comparer; }
}
public T Value {
get { return m_value; }
}
public ComparerNode(IComparer<T> comparer, T value) {
if (comparer == null) {
throw new ArgumentNullException("comparer");
}
m_comparer = comparer;
m_value = value;
}
public override int GetHashCode() {
if (m_value == null) {
return 0;
}
return m_value.GetHashCode();
}
public override bool Equals(object obj) {
var other = obj as ComparerNode<T>;
if (other == null) {
return false;
}
return 0 == m_comparer.Compare(m_value, other.m_value);
}
#region IComparable<ComparerNode<T>> Members
public int CompareTo(ComparerNode<T> other) {
if (other == null) {
return 1;
}
return m_comparer.Compare(m_value, other.m_value);
}
#endregion
public static bool operator <(ComparerNode<T> left, ComparerNode<T> right) {
return Comparer<ComparerNode<T>>.Default.Compare(left, right) < 0;
}
public static bool operator >(ComparerNode<T> left, ComparerNode<T> right) {
return Comparer<ComparerNode<T>>.Default.Compare(left, right) > 0;
}
public static bool operator ==(ComparerNode<T> left, ComparerNode<T> right) {
return EqualityComparer<ComparerNode<T>>.Default.Equals(left, right);
}
public static bool operator !=(ComparerNode<T> left, ComparerNode<T> right) {
return !EqualityComparer<ComparerNode<T>>.Default.Equals(left, right);
}
}
public static class ComparerNode {
public static ComparerNode<T> Create<T>(IComparer<T> comparer, T value) {
return new ComparerNode<T>(comparer, value);
}
public static ComparerNode<T> Create<T>(T value)
where T : IComparable<T> {
return new ComparerNode<T>(Comparer<T>.Default, value);
}
}