example.cpp

#include <iostream>
#include <vector>
#include <functional>

double func(double x, double y, const std::function<bool(double, double)>& f) {
    return f(x,y) ? x+y : x*y;
}

int main() {
    std::vector<std::pair<double, double>> vector;

    std::function<bool(double, double)> condition = [&vector, A = 2, B = 1](double x, double y) {
        vector.push_back({x, y});
        return A * x == B * y;
    };

    std::cout << "res = " << func(0.5, 1, condition) << std::endl;
    std::cout << "res = " << func(1.5, 3, condition) << std::endl;
    std::cout << "res = " << func(1.5, 2, condition) << std::endl;
    std::cout << "res = " << func(7.5, 1, condition) << std::endl;

    for (const auto & it : vector ) {
        std::cout << it.first << " " << it.second << std::endl;
    }
    return 0;
}