Function with array returning 0 Visual Basic

Question

I'm quite new at using arrays and functions in Visual Basic and I cannot seem to figure this out. My problem is that whenever I call the function Fibo it returns 0 no matter the value of n I give it. I'm sure the error is pretty basic.

Any pointer would be really appreciated!

Public Function fibo(n As Integer) As Integer

    Dim arrayFib(n + 1) As Integer 'declare array to hold fibonacci

    arrayFib(0) = 0 'idem
    arrayFib(1) = 1 'declare start value

    Dim i As Integer = 2 'start position

    While i <= n
        arrayFib(i) = arrayFib(i - 1) + arrayFib(i - 2)
        i = 1 + i

    Return arrayFib(i)

You missed End While. Just copy/paste mistake, or there is no End While in your code? — MarcinJuraszek
– MarcinJuraszek, Commented Sep 19, 2013 at 20:29
i becomes n + 1 and that value in the array is 0 (default value of INT). And also, should have End While (should even through an index out of bound exception). — Styxxy
– Styxxy, Commented Sep 19, 2013 at 20:29
@Cybȫʁgϟ37 It's an array of Integers, so there is no problem about the returning of a value (the type). — Styxxy
– Styxxy, Commented Sep 19, 2013 at 20:35

Hans Passant · Accepted Answer · 2013-09-19 20:41:56Z

3

Dim arrayFib(n + 1) As Integer 'declare array to hold fibonacci

We can sort of guess where that +1 came from. You added it because your original code crashed with an IndexOutOfRangeException. Caused by you returning arrayFib(i), i was incremented to be larger than n, its value is n+1 after the loop. And thus returns the value of an element that was never assigned. You didn't fix it correctly :)

Fix the array declaration back the way it was and return arrayFib(n) instead.

answered Sep 19, 2013 at 20:41

Hans Passant

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1 Comment

Chris Dunaway Over a year ago

If n is the number of Fibonacci digits to return, then the array declaration should be Dim arrayFib(n - 1) As Integer since in VB, the value specified when declaring an array is the upper bound, not the array size.

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