sieve of eratosthenes vba code explanation

[wannabe11]

Hello Guys

i need some help in understanding the following vba code

Sub Sieve()
    Const n         As Long = 10 ' numbers to test
    Dim colCand     As Collection   ' candidates
    Dim aiPrim()    As Long         ' primes for output
    Dim iPrim       As Long         ' a prime
    Dim nPrim       As Long         ' running count of primes
    Dim i           As Long         ' scratch index
 
    Set colCand = New Collection
    ReDim aiPrim(1 To n / (Log(n) - 2)) ' high estimate for nPrim
 
    ' initialize candidates
    For i = 2 To n
        colCand.Add Item:=i, Key:=CStr(i)
    Next i
 
    ' we'll be trying to delete numbers in colCand that were already deleted
    On Error Resume Next
 
    Do While colCand.Count
        ' first number in colCand is a prime
        nPrim = nPrim + 1
        iPrim = colCand(1)
        aiPrim(nPrim) = iPrim
        colCand.Remove 1
 
        ' remove all multiples
        For i = 2 To n \ iPrim
            colCand.Remove CStr(i * iPrim)
        Next i
    Loop
 
    'list 'em
    Range("A1").Resize(nPrim).Value = WorksheetFunction.Transpose(aiPrim)
    Beep
End Sub

the code is not mine , and allthough there are comments and i know it generate prime numbers , i dont understand the do while loop code , i dont understand what it does in each line , if anyone can read it and explain it in a simple manner .

and yes i'v tried running the code line by line to figure it out without success.

thanks in advance for your help guys .

[Simon Lloyd]

 ' initialize candidates
    For i = 2 To n 
        colCand.Add Item:=i, Key:=CStr(i) 
    Next i

Collects the number of prime number candidates

Do While colCand.Count 
         ' first number in colCand is a prime
        nPrim = nPrim + 1 
        iPrim = colCand(1) 
        aiPrim(nPrim) = iPrim 
        colCand.Remove 1 
         
         ' remove all multiples
        For i = 2 To n \ iPrim 
            colCand.Remove CStr(i * iPrim) 
        Next i 
    Loop

DoWhile keeps running the code below for each iteration, the iterations are set by the collection of candidate numbers.
Loop simply sends it back to DoWhile until colCand count has been exhausted.

[wannabe11]

 ' initialize candidates
    For i = 2 To n 
        colCand.Add Item:=i, Key:=CStr(i) 
    Next i

Collects the number of prime number candidates

Do While colCand.Count 
         ' first number in colCand is a prime
        nPrim = nPrim + 1 
        iPrim = colCand(1) 
        aiPrim(nPrim) = iPrim 
        colCand.Remove 1 
         
         ' remove all multiples
        For i = 2 To n \ iPrim 
            colCand.Remove CStr(i * iPrim) 
        Next i 
    Loop

DoWhile keeps running the code below for each iteration, the iterations are set by the collection of candidate numbers.
Loop simply sends it back to DoWhile until colCand count has been exhausted.

i dont know understand the part where the code detect the prime numbers and then seperate them .

[Simon Lloyd]

Is this homework or an assignment?

[SamT]

Do While... While expects a Boolean
A numerical 0 is a Boolean False, all other numbers are Boolean True

I like being specific when converting Variable Types...

Do While CBool(colCand.Count)