Prime Number

[Daniel W.]

Hello,

i wrote a programm that checks if a number is a prime number or not.

$zahl = InputBox("Zahl angeben", "Geben Sie an welche Zahl zu überprüfen ist.")
            If $zahl = 3 Then
            MsgBox(0, "", "Primzahl")
            ElseIf $zahl = 5 Then
            MsgBox(0, "", "Primzahl")
            ElseIf $zahl = 7 Then
            MsgBox(0, "", "Primzahl")
            ElseIf $zahl = 529 Then
            MsgBox(0,"", "Keine Primzahl")
            Else
            $I_Result = _MathCheckDiv($zahl, 2)
            If $I_Result = 2 Then
            MsgBox(0,'','Keine Primzahl')
            Else 
            $I_Result = _MathCheckDiv($zahl, 3)
            If $I_Result = 2 Then
            Msgbox(0, "", "Keine Primzahl")
            Else
            $I_Result = _MathCheckDiv($zahl, 5)
            If $I_Result = 2 Then
            Msgbox(0, "", "Keine Primzahl")
            Else
            $I_Result = _MathCheckDiv($zahl, 7)
            If $I_Result = 2 Then
            Msgbox(0, "", "Keine Primzahl")
            Else
            Msgbox(0, "", "Primzahl")
            EndIf
            EndIf
            EndIf
            EndIf 
            EndIf

If you have ideas to improve it, just tell me

Edited April 13, 2006 by Daniel W.

[RazerM]

Hmmm i suppose its just a coincidence you posted this after i posted my prime number thing lol

[Daniel W.]

Our codes do the same or?

Cuz they are different in whole way

[RazerM]

It appears that both our original ideas don't work. Try testing 529 (23*23) it says it is prime which it isn't as Wus told me in my thread. I have come up with this

;===============================================================================
;
; Function Name:   _IsPrime
; Description:: Check if a number is prime or not
; Parameter(s): $i_num - Number to check
; Requirement(s):  Math.au3
; Return Value(s): 1 - Number is prime
;                  0 - Number is not prime
; Author(s):       RazerM
;
;===============================================================================
;
Func _IsPrime($i_num)
    If $i_num > 3 Then
        If Mod($i_num, 2) = 0 Then Return 0
        If Mod($i_num, 3) = 0 Then Return 0
    EndIf
    Dim $divisor, $increment, $maxdivisor
    $divisor = 5
    $increment = 2
    $maxdivisor = Sqrt($i_num) + 1

    Do
        If Mod($i_num, $divisor) = 0 Then Return 0
        $divisor = $divisor + $increment
        $increment = 6 - $increment
    Until $divisor > $maxdivisor
    Return 1
EndFunc

which works better but says 5 isnt prime (any ideas?)

[Daniel W.]

I updated mine a bit for 529 and those numbers that havn't worked but dunno why yours is not working. Maybe because 5 is standart divisor?????? Just an idea

Edited April 13, 2006 by Daniel W.

[blindwig]

How about this:

Func _IsPrime($iNum)
    $iNum=Abs($iNum)
    Local $iMax = $iNum, $iDiv = 2, $fDiv = 0
    While Not $fDiv And $iDiv < $iMax
        $iMax = Int($iNum/$iDiv)
        $fDiv = $iMax = $iNum/$iDiv
        $iDiv += 1
    WEnd
    Return $fDiv = 0
EndFunc

Or, use the sqrt as RazorM did:

Func _IsPrime($iNum)
    $iNum=Abs($iNum)
    Local $iMax = Sqrt($iNum) + 1, $iDiv = 2, $fDiv = 0, $iTemp
    While Not $fDiv And $iDiv < $iMax
        $iTemp = $iNum/$iDiv
        $fDiv = Int($iTemp) = $iTemp
        $iDiv += 1
    WEnd
    Return $fDiv = 0
EndFunc

Edited April 13, 2006 by blindwig