Prime Number Test

[jacksparrow]

Hi
Got 2 errors
the program should let me enter number and check whether its a prime or not


Error 1 error C2668: 'sqrt' : ambiguous call to overloaded function c:\users\hani\test4\test4\code.cpp 15

Error 2 fatal error C1903: unable to recover from previous error(s); stopping compilation c:\users\hani\test4\test4\code.cpp 15

# include <iostream>
# include <cmath>
using namespace std;

int main () { 

    int n;
    int i;
    int is_prime=true;

    cout << " enter a number ";
    cin >>n;

    i = 2;
    while ( i <= sqrt(n)) {
        if ( n % i ==0)
            is_prime = false;
        i++;
    }

    if ( is_prime )
        cout << " the number is prime "<<endl;
    else
        cout << " is not prime number "<<endl;

system ("PAUSE");
return 0;

} 

[Philip Nicoletti]

You are taking the sqrt of an int variable. The compiler does not know which overload
of sqrt to use (float ? double ?). You need to explicitly tell the compiler what to use:

    while ( i <= sqrt( static_cast<double>(n) ) ) {

[jacksparrow]

Thanks Philip

[Lindley]

As an aside, a very easy way to convert an int to a double is to add 0.0, for instance

while ( i <= sqrt( n + 0.0 ) ) {

[jacksparrow]

checked it lindley nice work

[ovidiucucu]

[ Moved thread ]

[Richard.J]

int is_prime=true;

should be

bool is_prime=true;

to avoid implicit conversions.