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IsPrime

Posted On 2011-12-31 by FortyPoundHead
Keywords: ASP VBScript Math Functions
Tags: ASP Scripting VBScript Windows
Views: 2019


This handy little vbscript function checks to see if a number is a primary number.

Prime numbers are commonly found in encryption schemes that use Public/Private keys.

Pass it a number, and it will return a true/false value depending on the "primeness" of the number.

It first assumes that the number passed is false. Then it simply checks if it is less than 2, divisible by two, or has a square.

If it makes it past those checks, then it must be prime. The value is set and returned to the caller.

'**************************************
' Name: IsPrime
' Description:Checks to see if a number is a primary number. Prime numbers are commonly found in encryption schemes that use Public/Private keys.
'**************************************

function IsPrime(ByRef pLngNumber)

Dim lLngSquare
Dim lLngIndex

IsPrime = False

if pLngNumber < 2 Then Exit function
if pLngNumber Mod 2 = 0 Then Exit function

lLngSquare = Sqr(pLngNumber)

For lLngIndex = 3 To lLngSquare Step 2

if pLngNumber Mod lLngIndex = 0 Then Exit function

Next

IsPrime = True

End function


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