Wrapping C with C++ in .NET

Listing 5: Using the numeric objects from VB.NET.

Imports System
Imports System.Runtime.InteropServices
Imports NAGLIB

Module Module1
   Public Class DCLASS
      Inherits NAG_FUNCTIONS
      Public Function the_integrand_c(ByVal x As Double) As Double
         Dim pi As Double
         Dim val As Double
         pi = Math.PI
         val = (x * Math.Sin(x * 30) / 1 - x * x / (pi * pi * 4))
         Return val
      End Function
   End Class
   Sub Main()
      Dim x, the_answer As Double
      Dim flag, j, tda, n As Integer
      Dim a(,), r(), a1, b1, abserr As Double
      Dim tt As New DCLASS()
      Dim myfun As New INTEGRAND_FUN_TYPE(AddressOf tt.the_integrand_c)
      a1 = 0
      b1 = Math.PI * 2
      flag = 0
      tt.QUADRATURE(a1, b1, the_answer, abserr, flag, myfun)
      Console.WriteLine("The integral (default number of 
                                     subintervals) = {0,8:F4}", the_answer)
      tt.QUADRATURE_max_subint = 3
      flag = 0
      tt.QUADRATURE(a1, b1, the_answer, abserr, flag, myfun)
      Console.WriteLine("The integral (number of subintervals 
                                     set to 3) = {0,8:F4}", the_answer)
      x = -1
      the_answer = tt.CUM_NORM(x)
      Console.WriteLine("The value of the cumulative  normal = {0,8:F4}", the_answer)
      flag = 0
      n = 4
      tda = n
      ReDim r(n - 1)
      ReDim a(n - 1, n - 1)
      ' first row
      a(0, 0) = 0.5
      a(0, 1) = 0
      a(0, 2) = 2.3
      a(0, 3) = -2.6
      'second row
      a(1, 0) = 0
      a(1, 1) = 0.5
      a(1, 2) = -1.4
      a(1, 3) = -0.7
      ' third row
      a(2, 0) = 2.3
      a(2, 1) = -1.4
      a(2, 2) = 0.5
      a(2, 3) = 0
     'fourth row
     a(3, 0) = -2.6
     a(3, 1) = -0.7
     a(3, 2) = 0
     a(3, 3) = 0.5
     tt.REAL_SYMM_EIGEN(n, a(0, 0), tda, r(0), flag)
     Console.Write("The Eigenvalues are:")
     For j = 0 To n - 1
        Console.Write("{0,8:F4}", r(j))
     Next j
     Console.WriteLine()
  End Sub
End Module