CODEWITHSUNDEEP
vba
TylerC
TylerC

Reputation: 49

VBA - Overflow error at For Loop entry

I'm trying to write a function that takes as input a square matrix that should have in its cells

likes this 3 x 3 matrix (first cell contains # 10, second cell # 5, etc.):

10  5   1

9   6   

4

Before I do anything with this matrix, I need to verify that the cells on and above the diagonal contain positive numbers and that the other cells are empty. I wrote the code below.

The problem is that it gives me an overflow error at the second For loop, and for the life of me, I don't understand why. With a 3 x 3 matrix (that is, n = 3, p = 3), the first line of the second For loop would be: For i = 3 to 2 Step -1. What is the problem here?

Option Base 1

Private Sub triangle1()

    Dim y As Variant
    y = Application.InputBox( _
    Prompt:=" Choose a square matrix in a worksheet : ", Type:=8)

    Dim i As Byte, j As Byte, n As Byte, p As Byte, s As Byte
    n = UBound(y, 1)
    p = UBound(y, 2)

    Debug.Print LBound(y, 1), n, p
    s = 1
    If n <> p Then
        Debug.Print "False"
        Exit Sub
    Else
        ' First For loop
        For i = 1 To n
            For j = 1 To p
                If y(i, j) <= 0 Or Not IsNumeric(y(i, j)) Then
                    Debug.Print "False"
                    Exit Sub
                End If
            Next
            p = p - 1
        Next

        ' Second For loop
        For i = n To 2 Step -1
            s = s + 1
            For j = s To p
                If Not IsEmpty(y(i, j)) Then
                    Debug.Print "False"
                    Exit Sub
                End If
            Next
        Next
        Debug.Print "True"
    End If
End Sub

Upvotes: 1

Views: 2237

Answers (1)

Alexis Olson
Alexis Olson

Reputation: 40224

The problem is with the byte types. If you replace them with Integer or Long it should run.

The reason is that byte cannot handle negative numbers (only integers 0-255), so it doesn't know what to do with the Step -1 since the step is the same type as the iterator.

Upvotes: 4

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