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PrimeNumbers\\error C2668

 
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PrimeNumbers\\error C2668
climax
post 2 Sep, 2007 - 02:53 AM
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Hi there...
I'm working on a program that writes out all the prime numbers up to 1000. I think I got the program almost right, but when i compile it i get the C2668 error ('sqrt' : ambigious call to overloaded function). Can anyone see what might be the problem here? if so, thanks alot biggrin.gif

CODE

#include <iostream>
#include <math.h>

using namespace std;

bool isPrime (int num)
{

    // no number can divide into 0
    if(num == 0)
    return true;

    // make sure its not negative
    num = abs(num);

    for(int i=2; i<=sqrt(num); i++)
    {
    if(num % i == 0)
    {
        return false;
    }  
    return true;  
    }
}
int main()
{
    for (int i=2;i<1000;i++)
    {
        bool number = isPrime(i);;
        if (number == true)
        {
            cout<<i<<"\t";
        }
    }
    cout<<"\n"<<endl;
}
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Bench
post 2 Sep, 2007 - 03:02 AM
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sqrt isn't designed to take int, but it has 3 available overloads where 'int' is allowed to implicitly cast, so the call is ambiguous - If you provide an explicit cast, the compiler will know which one to use.

CODE
    for(int i=2; i<=sqrt(  static_cast<double>(num) ); i++)  



edit, On a minor point, you could change <math.h> , which is a deprecated header in C++, to <cmath> to ensure you're using the latest standard version of the 'C' math header.


By the way, all your isprime() function seems to do is output odd numbers. have another think about how you could find prime numbers (You might find this idea interesting.. http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes )

This post has been edited by Bench: 2 Sep, 2007 - 03:11 AM
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climax
post 2 Sep, 2007 - 03:08 AM
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QUOTE(Bench @ 2 Sep, 2007 - 04:02 AM) *

sqrt isn't designed to take int, but it has 3 available overloads where 'int' is allowed to implicitly cast, so the call is ambiguous - If you provide an explicit cast, the compiler will know which one to use.

CODE
    for(int i=2; i<=sqrt(  static_cast<double>(num) ); i++)  



edit, On a minor point, you could change <math.h> , which is a deprecated header in C++, to <cmath> to ensure you're using the latest standard version of the 'C' math header.



ah.. nice smile.gif that solved the c2668 error....
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climax
post 2 Sep, 2007 - 03:35 AM
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QUOTE(Bench @ 2 Sep, 2007 - 04:02 AM) *

By the way, all your isprime() function seems to do is output odd numbers. have another think about how you could find prime numbers (You might find this idea interesting.. http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes )


thnx again! got the function right now.. had to change out a bit yea wink2.gif
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