Question Whats Wrong with this Fibonacci Application?

[Haxaro]

For my application, i need the user to input a number, and the application will work out the highest possible Fibonacci number below the user inputed number.

At the moment, my application is providing non-Fibonacci numbers, which is a problem.

Here is the code:

Public Class Form1

    Dim Input = Input1.Text
    Dim output = Output1.Text

    Private Sub Main(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Work.Click

        ' Declarations
        Dim FirstNum = 1 'Declare
        Dim OverFlow = 1 'Declare
        Dim BackUp = 1 'Declare
        Dim PreResult = 1 'Declare
        Dim Result = 1 'Declare
        Dim FinalResult = 1 'Declare


        Do Until Result > Input() ' Loop until the result is greater than the user inputed text
            FirstNum = BackUp ' Prepare for next loop
            PreResult = Result + FirstNum ' Add X + Y = Z
            BackUp = PreResult ' Prepare for next loop
            Result = PreResult ' Prepare for next loop
        Loop

        If Result > Input() Then ' When the result is greater than the user inputed text, run:
            FinalResult = Result - BackUp ' Go back one Fibonacci number
            output = FinalResult ' Output the final Number lower than the user inputed text
        End If

    End Sub
End Class

Any help would be greatly appreciated. Thanks!
Haxaro

 

[InertiaM]

1. Option Strict should be on.

2. Why are you using Textboxes, when a NumericUpDown control would be far more suited to this?

3.

        Dim DesiredValue As Integer = 372

        Dim FirstNum As Integer = 0
        Dim SecondNum As Integer = 1
        Dim Result As Integer = 0

        While FirstNum + SecondNum < DesiredValue
            Result = FirstNum + SecondNum
            FirstNum = SecondNum
            SecondNum = Result
        End While

        Result = SecondNum

 

[Haxaro]

Great Help

Thanks. That was a great help, but i dont know too much about option strict, so im not sure how i am ment to convert a string (text box) to a integer in option strict...

Option Strict On
Public Class Form1

    Private Sub Main(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        Dim Value As Integer = ***Input.Text***
        Dim FirstNum As Integer = 1
        Dim SecondNum As Integer = 1
        Dim Result As Integer = 1

        Do Until FirstNum + SecondNum < Value
            Result = FirstNum + SecondNum
            FirstNum = SecondNum
            SecondNum = Result
        Loop

        Result = SecondNum
        ***OutPut.Text = Result***
    End Sub
End Class

Help with the *** sections would be appreciated. Thanks!

 

[Haxaro]

Didn't Work

I just got it working, but it still doesnt get the correct answer..

Option Strict On
Public Class Form1

    Private Sub Main(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Work.Click

        Dim Value As Integer = CInt(Input1.Text)
        Dim FirstNum As Integer = 1
        Dim SecondNum As Integer = 1
        Dim Result As Integer = 0
        Dim Old As Integer = 0
  
        Do Until FirstNum + SecondNum > Value
            Result = FirstNum + SecondNum
            Old = FirstNum
            FirstNum = SecondNum
            SecondNum = Result
        Loop


        Result = Result - Old
        Output1.Text = CStr(Result)
    End Sub
End Class

 

[InertiaM]

        Result = SecondNum
        Output1.Text = Result.ToString

and, for reference, Fibonacci starts at 0 and 1, not 1 and 1, so your code should be:-

        Dim FirstNum As Integer = 0
        Dim SecondNum As Integer = 1

 

[Haxaro]

Well either way, it still isnt working. It comes up with a fibonacci number, but it isnt the highest... any reasons why - or how i can fix this?

Option Strict On
Public Class Form1

    Private Sub Main(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Work.Click

        Dim Value As Integer = CInt(Input1.Text)
        Dim FirstNum As Integer = 0
        Dim SecondNum As Integer = 1
        Dim Result As Integer = 1
        Dim Real As Integer = 1
  
        Do Until FirstNum + SecondNum >= Value
            Result = FirstNum + SecondNum
            Real = SecondNum
            FirstNum = SecondNum
            SecondNum = Result
        Loop


        Output1.Text = CStr(Real)
    End Sub
End Class

 

[InertiaM]

How about giving an example of what values you are trying, and what result it is giving? I didnt pass my course in mind reading

 

[euromax]

Fibonacci sequence

Public Function Fibonacci(ByVal mynum As System.Int64) As System.Int64
If mynum = 0 Then
Return 0
ElseIf mynum = 1 Then
Return 1
Else
Return Fibonacci(mynum - 1) + Fibonacci(mynum - 2)
End If
End Function

Public Function closestFibonnacci(ByVal mynum As System.Int64) As System.Int64
Dim index, result As System.Int64
Do
result = Fibonacci(index)
index += 1
Loop Until result >= mynum

Do
result = Fibonacci(index)
index -= 1
Loop Until result <= mynum
Return result
End Function

' this code works. Place a numeric updown control and a textbox on your form and display the Fibonacci number closest to the user input value using an instruction like:

TextBox1.Text= closestFibonacci(CLng(NumericUpDown1.value)).ToString

You will need the 'CLng' if Option Strict is on.