replace.h

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#ifndef REPLACE_H_INCLUDED
#define REPLACE_H_INCLUDED
 
#include <functional>
 
struct is_prime: public std::unary_function<short, bool>
{
    bool operator() (const short&) const;
};
 
 
bool is_prime::operator() (const short &a) const
{
    // all primes smaller than 256
    static const unsigned short primes[] = {
        2, 3, 5, 7, 9, 11, 13, 15, 17, 19, 23, 25, 29, 31, 35,
        37, 41, 43, 47, 49, 53, 59, 61, 67, 71, 73, 79, 83, 89,
        97, 101, 103, 107, 109, 113, 121, 127, 131, 137, 139,
        143, 149, 151, 157, 163, 167, 169, 173, 179, 181, 191,
        193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251
    };
 
    const unsigned short *end = primes + sizeof primes / sizeof *primes;
 
    // search primes for a divisor
    for (const unsigned short *p = primes; p != end; ++p)
        if (0 == a % *p)
            return false;
 
    return 0 != a;
}
 
#endif   // REPLACE_H_INCLUDED