pyt.cpp

/* $ g++ -Wall -std=c++0x pyt.cpp */

#include <iostream>

struct triple {
    int x, y, z;
};

class pyt {
public:
    pyt() : state_{1,1,1} {
        next();
    }

    const triple& get() const { return state_; }

    void next() {
        do { inc(); }
        while (!condition());
    }

private:
    void inc() {
        if (++state_.y > state_.z) {
            if (++state_.x > state_.z) {
                ++state_.z;
                state_.x = 1;
            }
            state_.y = state_.x;
        }
    }

    bool condition() const {
        return state_.x * state_.x + state_.y * state_.y ==
            state_.z * state_.z;
    }

    triple state_;
};

int main(int argc, char** argv) {
    pyt p;

    for (;;) {
        const triple& t = p.get();
        std::cout << t.x << ", " << t.y << ", " << t.z << std::endl;
        p.next();
    }

    return 0;
}