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List:       kde-devel
Subject:    Re: Prime number problems
From:       Michael Pyne <pynm0001 () comcast ! net>
Date:       2004-04-23 18:28:27
Message-ID: 200404231428.34000.pynm0001 () comcast ! net
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On Friday 23 April 2004 11:36, M2George wrote:
> The following code fragment works partialy, it list all primes in range but
> also includes "1" as a prime.
> How do I get rid of it?

This is your problem:
>             for(int i = iNumber1; i <= iNumber2; i++)
>             {
>                 for (int iFactor = 2; iFactor < i; ++iFactor)

Let's say that iNumber1 equals 1.  You have this:
for (i = 1; i < iNumber2; i++)
  for (iFactor = 2; iFactor < 1; ++iFactor)
...

Your loop starts off by setting isPrime to true, but your second for loop will 
never run because 2 is greater than, not less than 1.  Since the second loop 
doesn't run, the i == 1 test won't be encountered, and isPrime will remain 
true.

The simplest fix is to set isPrime to be false right before the second for 
loop.  However, if I were you, I'd improve that loop using the suggestions of 
the other replies to your e-mail.

Regards,
 - Michael Pyne
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