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' Description:
'   Calculates the multiplicity of a knot.
' Parameters:
'   knots - an array of knot values
'   knot_index - the index of the knot to determine multiplicity
' Returns:
'   The multiplicity if successful
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Function KnotMultiplicity(knots, knot_index)

  Dim knot_count, mult, index, t

  index = knot_index
  knot_count = UBound(knots)

  If (index < 0 Or index > knot_count) Then
    KnotMultiplicity = Null
    Exit Function
  End If

  t = knots(index)
  mult = 1

  Do While (index < knot_count)
    If (knots(index + 1) - t) > 1.0e-12 Then Exit Do
    index = index + 1
    mult = mult + 1
  Loop

  KnotMultiplicity = mult

End Function