prime1.cpp

侯捷关于C++ STL的经典翻译作品《C++ 标准程序库》的书籍源代码

//p121
#include <iostream>
#include <list>
#include <algorithm>
#include <cstdlib>      // for abs()
using namespace std;

// predicate, which returns whether an integer is a prime number
bool isPrime (int number)
{
    // ignore negative sign
    number = abs(number);
    // 0 and 1 are no prime numbers
    if (number == 0 || number == 1) {
        return false;
    }
        
    // find divisor that divides without a remainder
    int divisor;
    for (divisor = number/2; number%divisor != 0; --divisor) {
        ;
    }

    // if no divisor greater than 1 is found, it is a prime number
    return divisor == 1;
}

int main()
{
    list<int> coll;

    // insert elements from 24 to 30
    for (int i=24; i<=30; ++i) {
        coll.push_back(i);
    }

    // search for prime number
    list<int>::iterator pos;
    pos = find_if (coll.begin(), coll.end(),    // range
                   isPrime);                    // predicate
    if (pos != coll.end()) {
        // found
        cout << *pos << " is first prime number found" << endl;
    }
    else {
        // not found
        cout << "no prime number found" << endl;
    }
}