 Find Prime Number, find prime number code |
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 Mar 28 2007, 01:27 PM
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#1
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Newbie [Level 1]  Group: Members Posts: 19 Joined: 7-May 06 Member No.: 23,209  |
CODE Public Function GetPrimeNo (InNoWanted As Integer) As Long
Dim lPrimes() As Long Dim lTrial As Long Dim lCount As Integer Dim lFound As Integer Dim lCounter As Integer ReDim lPrimes(InNoWanted) lTrial = 5 lCount = 3 lFound = 0 'Define the first three prime number ' > lPrimes(0) = 2 lPrimes(1) = 3 lPrimes(2) = 5 Do lTrial = lTrial + 2 lFound = 0 For lCounter = 0 To lCount - 1 lFound = (lTrial Mod lPrimes(lCounter)) = 0 If lFound Then Exit For End If lCounter = lCounter + 1 Next lCounter If lFound = 0 Then lPrimes(lCount) = lTrial lCount = lCount + 1 End If Loop While (lCount < InNoWanted) GetPrimeNo = lPrimes(InNoWanted - 1) End Function |
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Mar 28 2007, 08:04 PM
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#2
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Super Member Group: Members Posts: 397 Joined: 9-June 06 From: Wisconsin Member No.: 24,924 |
Interesting function. What exactly is the purpose of the argument InNoWanted?
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Apr 4 2007, 11:31 AM
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#3
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Neurotical Squirrel Group: [HOSTED] Posts: 579 Joined: 4-November 04 From: Novi Sad, Vojvodina Member No.: 2,127 |
That's great function... I'm really no good at math, and I can emember that on one or two occasions I needed such a function, to find a prime number... I'll keep this in my code base, for future reference... Great work
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May 9 2007, 09:04 PM
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#4
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Privileged Member Group: [HOSTED] Posts: 775 Joined: 13-April 07 From: mreža Member No.: 41,558 |
Are you sure that this works as I checked it at least I scanned it and it seems like it will return an error because of for loop. I am quite new to the visual basic but I am still learning that is in the process of learning. Maybe I am just wrong when I have more time I'll check it.
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May 9 2007, 11:08 PM
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#5
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Super Member Group: Members Posts: 397 Joined: 9-June 06 From: Wisconsin Member No.: 24,924 |
I am reviewing your function once and you have a couple mistakes so far. I've been using VB for about 11 years now, and I will point them out to you, and post a bug free function.
You didn't post any information about how your function works. From what I can gather, the argument InNoWanted, will return the nth prime number, where n is the value of InNoWanted. For example, your function should produce the following results. -------------------------------------- | InNoWanted | Value Returned | -------------------------------------- | 1 | 2 | -------------------------------------- | 2 | 3 | -------------------------------------- | 3 | 5 | -------------------------------------- | 4 | 7 | -------------------------------------- The first error I have encountered is this that a value of zero will mess stuff up. You should add a check to make sure a value of zero is not entered: CODE Public Function GetPrimeNo(InNoWanted As Integer) As Long Dim lPrimes() As Long Dim lTrial As Long Dim lCount As Integer Dim lFound As Integer Dim lCounter As Integer If InNoWanted = 0 Then Exit Function End If Nextly, it returns an error because you do not have enough elements in your array. You define 3 below this ReDim statement. Therefore you should add 3 to the amount of elements to create. CODE ReDim lPrimes(InNoWanted + 3) You also commented out some code. You need that to have your program run correctly. CODE 'Define the first three prime number lPrimes(0) = 2 lPrimes(1) = 3 lPrimes(2) = 5 Other than that, you have no other programming mistakes in your code. Below is the fixed version: CODE Public Function GetPrimeNo(InNoWanted As Integer) As Long Dim lPrimes() As Long Dim lTrial As Long Dim lCount As Integer Dim lFound As Integer Dim lCounter As Integer If InNoWanted = 0 Then Exit Function End If ReDim lPrimes(InNoWanted + 3) lTrial = 5 lCount = 3 lFound = 0 'Define the first three prime number lPrimes(0) = 2 lPrimes(1) = 3 lPrimes(2) = 5 Do lTrial = lTrial + 2 lFound = 0 For lCounter = 0 To lCount - 1 lFound = (lTrial Mod lPrimes(lCounter)) = 0 If lFound Then Exit For End If lCounter = lCounter + 1 Next lCounter If lFound = 0 Then lPrimes(lCount) = lTrial lCount = lCount + 1 End If Loop While (lCount < InNoWanted) GetPrimeNo = lPrimes(InNoWanted - 1) End Function |
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