# VB Vector Range Example

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```Imports System

Imports CenterSpace.NMath.Core
Imports Range = CenterSpace.NMath.Core.Range

Namespace CenterSpace.NMath.Examples.VisualBasic

A .NET example in Visual Basic showing how to use the indexing class Range with the vector classes.
Module VectorRangeExample

Sub Main()

Dim length As Integer = 10

Console.WriteLine()

Dim u As New DoubleVector(length, 0, 1)
Console.WriteLine("u = " & u.ToString())   u = [0 1 2 3 4 5 6 7 8 9]

Last five elements of the vector u:
Dim uLast5 As DoubleVector = u(New Range(5, length - 1))
Console.WriteLine("uLast5 = " & uLast5.ToString())   uLast5 = [5 6 7 8 9]

Could also get this by specifying all elements from the 6th to the end using
the End value from the Position enum
uLast5 = u(New Range(5, Position.End))
Console.WriteLine("uLast5 = " & uLast5.ToString())   uLast5 = [5 6 7 8 9]

You can use negative strides too. Here is the vector u, reversed.
Dim uRev As DoubleVector = u(New Range(length - 1, Position.Start, -1))
Console.WriteLine("uRev = " & uRev.ToString())   uRev = [9 8 7 6 5 4 3 2 1 0]

Notice that when you create a new DoubleVector using the Range or Slice class,
you are creating a different "view" of the vectors data. That is, the
DoubleVector instance returned by the indexing operator taking a Range object,
and the DoubleVector instance being indexed share the same data:
uRev(0) = 0
Console.WriteLine("uRev = " & uRev.ToString())   uRev = [0 8 7 6 5 4 3 2 1 0]
Console.WriteLine("u = " & u.ToString())   u = [0 1 2 3 4 5 6 7 8 0]

Finally, we use the DoubleVector method Set(Range) to change the contents of u
to alternate values 0 and 1
Dim evenElts As New Range(0, Position.End, 2)
Dim oddElts As New Range(1, Position.End, 2)
u.Set(evenElts, 0)
u.Set(oddElts, 1)
Console.WriteLine("u = " & u.ToString())   u = [0 1 0 1 0 1 0 1 0 1]

Console.WriteLine()
Console.WriteLine("Press Enter Key")