PASSING AN ENTIRE ARRAY TO A PROCEDURE in .NET framework

Printer QR Code 2d barcode in .NET framework PASSING AN ENTIRE ARRAY TO A PROCEDURE

Here is a skeletal structure of a Visual Basic program that passes an entire array to a sub procedure. The first n elements are then assigned numerical values within the procedure. Note that the array is called x in the calling portion of the program, and v within the procedure. This is permissible, as long as the array arguments are of the same size and the same data type, and they appear in the same relative location within each argument list.

Dim x(10) As Integer, n As Integer . . . . . n = . . . . . Call Setup(x(), n) 'procedure reference 'or Setup x(), n Private Sub Setup(v() As Integer, n As Integer) Dim i As Integer For i = 0 to n v(i) = i ^ 2 Next i End Sub 'procedure definition

Since the array elements are passed by reference, the values assigned to the array elements within the procedure will be recognized elsewhere within the program (e.g., in the calling portion of the program).

Individual array elements (i.e., subscripted variables) may also be passed to procedures as arguments. Subscripted variables are written in the normal manner when they appear as arguments within a procedure reference. The corresponding arguments in the first line of the procedure definition may be either subscripted variables or ordinary variables, depending on the program logic.

This example illustrates how subscripted variables are passed to a procedure as arguments. In this case, we will assign single-precision values to the array elements 1 through 100 within the calling portion of the program. We then pass two consecutive array elements to the procedure, which returns the square root of the sum of their squares. This value is assigned to the first array element (i.e., array element x(0) ).

Dim x(100) As Single, i As Integer, n As Integer For i = 1 To 100 x(i) = i Next i . . . . . n = . . . . . x(0) = Hypotenuse(x(n), x(n + 1)) . . . . .

Private Function Hypotenuse(a As Single, b As Single) As Single Hypotenuse = Sqr(a ^ 2 + b ^ 2) End Function

If n is assigned a value of 3, what value will be assigned to x(0)

In the next example we see a complete Visual Basic project that passes both an entire array and a single array element as arguments.

In Example 7.2 we saw a complete Visual Basic program allowing the user to enter two numbers. The program determined the smaller of the two and displayed the result within a message box. Here is a variation of that program in which we utilize a three-element, one-dimensional array x to hold the numbers. We will place the two input values in elements x(1) and x(2), and then tag the smaller value by placing it in x(0), which we will then send to a message box. The user interface will be unchanged from Example 7.2. Hence, the control layout will be identical to that shown in Figs. 7.1 and 7.2. Here is the new source code.

Dim x(2) As Single Private Sub Command1_Click() x(1) = Val(Text1.Text) x(2) = Val(Text2.Text) Call Smallest(x()) End Sub

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CHAP. 8]

Private Sub Command2_Click() End End Sub Sub Smallest(x() As Single) Dim Text As String If (x(1) < x(2)) Then x(0) = x(1) Text = "a is smaller (a = " ElseIf (x(1) > x(2)) Then x(0) = x(2) Text = "b is smaller (b = " Else x(0) = x(1) Text = "Both values are equal (a, b = " End If Call Message(Text, x(0)) End Sub Sub Message(Text As String, Value As Single) Dim LineOut As String LineOut = Text & Str(Value) & ")" MsgBox LineOut End Sub

Note that the entire array x is passed to the sub procedure Smallest from Command1_Click. Within Smallest, the smaller of the two values is determined and assigned to x(0). Finally, the value of x(0), together with an appropriate message, are passed to sub procedure Message. Within Message, the message and the value of x(0) are combined into a single string. This string is then displayed within a message box. When the program is executed, it behaves in exactly the same manner as the earlier program shown in Example 7.2. Fig.s 7.3 and 7.4 show representative output.