Tuple<T1>.IStructuralEquatable.Equals Method

Parameters

• other
  Type: System.Object
  The object to compare with this instance.

• comparer
  Type: System.Collections.IEqualityComparer
  An object that defines the method to use to evaluate whether the two objects are equal.

Return Value

Type: System.Boolean
true if the current instance is equal to the specified object; otherwise, false.

Imports System.Collections

Public Class Tuple1Comparer : Implements IEqualityComparer
   Public Overloads Function Equals(ByVal x As Object, ByVal y As Object) As Boolean _
                   Implements IEqualityComparer.Equals
      ' Check if x is a floating point type. If x is, then y is.
      If TypeOf x Is Double Or TypeOf x Is Single Then
         ' Convert to Double values.
         Dim dblX As Double = CDbl(x)
         Dim dblY As Double = CDbl(y)
         If Double.IsNaN(dblX) Or Double.IsInfinity(dblX) Or _
            Double.IsNaN(dblY) Or Double.IsInfinity(dblY) Then
            Return dblX.Equals(dblY)
         Else
            Return Math.Abs(dblX - dblY) <= dblY * 0.0001
         End If
      Else
         Return x.Equals(y)
      End If
   End Function

   Public Overloads Function GetHashCode(ByVal obj As Object) As Integer _
                   Implements IEqualityComparer.GetHashCode
      Return obj.GetHashCode()
   End Function
End Class

Module Example
   Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      Dim doubleTuple1 = Tuple.Create(12.3455)

      Dim doubleTuple2 = Tuple.Create(16.8912)
      Dim doubleTuple3 = Tuple.Create(12.3449599)

      ' Compare first tuple with a Tuple(Of Double) with a different value.
      TestEquality(outputBlock, doubleTuple1, doubleTuple2)
      ' Compare first tuple with a Tuple(Of Double) with the same value.
      TestEquality(outputBlock, doubleTuple1, doubleTuple3)
   End Sub

   Private Sub TestEquality(ByVal outputBlock As System.Windows.Controls.TextBlock, ByVal tuple As Tuple(Of Double), ByVal obj As Object)
      Try
         outputBlock.Text += String.Format("{0} = {1}: {2}", tuple.ToString(), _
                                             obj.ToString, _
                                             DirectCast(tuple, IStructuralEquatable).Equals(obj, New Tuple1Comparer())) & vbCrLf

      Catch e As ArgumentException
         If obj.GetType.IsGenericType Then
            If obj.GetType().Name = "Tuple`1" Then
               outputBlock.Text += String.Format("Cannot compare a Tuple(Of {0}) with a Tuple(Of {1}).", _ 
                              tuple.Item1.GetType().Name, obj.Item1.GetType().Name) & vbCrLf
            Else
               outputBlock.Text += String.Format("Cannot compare a {0} with a {1}.", tuple.GetType().Name, _ 
                                                                     obj.GetType().Name) & vbCrLf
            End If
         Else
            outputBlock.Text += String.Format("Cannot compare a {0} with a {1}.", tuple.GetType().Name, _
                                                                  obj.GetType().Name) & vbCrLf
         End If
      End Try
   End Sub
End Module
' The example displays the following output:
'       (12.3455) = (16.8912): False
'       (12.3455) = (12.3449599): True

using System;
using System.Collections;

public class Tuple1Comparer : IEqualityComparer
{
   new public bool Equals(object x, object y)
   {
      // Check if x is a floating point type. If x is, then y is.
      if (x is double | x is float)
      {
         // Convert to Double values.
         double dblX = (double)x;
         double dblY = (double)y;
         if (Double.IsNaN(dblX) | Double.IsInfinity(dblX) |
             Double.IsNaN(dblY) | Double.IsInfinity(dblY))
            return dblX.Equals(dblY);
         else
            return Math.Abs(dblX - dblY) <= dblX * .0001;
      }
      else
      {
         return x.Equals(y);
      }
   }

   public int GetHashCode(object obj)
   {
      return obj.GetHashCode();
   }
}

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      var doubleTuple1 = Tuple.Create(12.3455);

      var doubleTuple2 = Tuple.Create(16.8912);
      var doubleTuple3 = Tuple.Create(12.3449599);

      // Compare first tuple with a Tuple<double> with a different value.
      TestEquality(outputBlock, doubleTuple1, doubleTuple2);
      //Compare first tuple with a Tuple<double> with the same value.
      TestEquality(outputBlock, doubleTuple1, doubleTuple3);
   }

   private static void TestEquality(System.Windows.Controls.TextBlock outputBlock, Tuple<double> tuple, object obj)
   {
      outputBlock.Text += String.Format("{0} = {1}: {2}", tuple.ToString(),
                                             obj.ToString(),
                                             ((IStructuralEquatable)tuple).Equals(obj, new Tuple1Comparer())) + "\n";
   }
}
// The example displays the following output:
//       (12.3455) = (16.8912): False
//       (12.3455) = (12.3449599): True