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isPrime()

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isPrime()

Jul 6th, 2007

I need to write a main() function, that loops over a bunch of
numbers from 0 to 100, calls another function called isPrime() for each of them, and print out the numbers that are prime.
I'm new to C++ and any help would be appreciated.

Last edited by forumposters; Jul 6th, 2007 at 9:08 pm.

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Narue

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Re: isPrime()

Jul 6th, 2007

>I'm new to C++ and any help would be appreciated.
At least start trying to solve your problem before asking for help. It makes us like you more and ignore you less.

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Re: isPrime()

Jul 6th, 2007

What narue said applies. But I'll help you a little: isPrime(int x)

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Re: isPrime()

Jul 7th, 2007

Here's what I've come up with so far:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
#include <iostream>
 
  bool IsPrime(int num)
  {
 if(num == 0)
   return true;
 
 num = abs(num);
 
  for(int i = 2; i <= sqrt(num); i++)
   if(num % i == 0)
  return false;
 
  return true;
  }
#include <iostream>

  bool IsPrime(int num)
  {
 if(num == 0)
   return true;

 num = abs(num);

  for(int i = 2; i <= sqrt(num); i++)
   if(num % i == 0)
  return false;

  return true;
  }

Last edited by ~s.o.s~; Jul 7th, 2007 at 3:38 am. Reason: Added code tags, learn to use them.

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Re: isPrime()

Jul 7th, 2007

You've been around over a year and haven't read the Rules yet? You also need to read this. It will explain that you need to tell us what problem you are having so we don't have to guess -- among other things

The 3 Laws of the Procrastination Society:
1) Never do today that which can be put off until tomorrow
2) Tomorrow never comes

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Narue

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Re: isPrime()

Jul 7th, 2007

>Here's what I've come up with so far
Somehow I find it hard to believe that you can write IsPrime but not the main driver to print the primes in the range [0..100). I'm guessing you were given IsPrime and told to write main, which means you've come up with nothing so far. But, the hard part is done already. All you need to do is loop from 0 to 100 and call IsPrime on the current number. If it returns true, print the number:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
for ( int i = 0; i < 100; i++ ) {
  if ( IsPrime ( i ) )
    cout<< i <<" is prime\n";
}
for ( int i = 0; i < 100; i++ ) {
  if ( IsPrime ( i ) )
    cout<< i <<" is prime\n";
}

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JRM

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Re: isPrime()

Jul 7th, 2007

•

Originally Posted by Narue

>Here's what I've come up with so far
Somehow I find it hard to believe that you can write IsPrime but not the main driver to print the primes in the range [0..100). I'm guessing you were given IsPrime and told to write main, which means you've come up with nothing so far.
[/code]

LOL! If some people would put half of the effort that they put into "avoiding work" into something productive, they would have had the task acomplished by now!

If laziness is truely the mother of invention, we have quite a group of potential inventors here!