Lab 4 OOM

#include <iostream>
#include <cmath>

typedef double (*func)(double);

double MP2(double x0, double h, double eps, func F) {
    double x1 = x0 - h;
    double x2 = x0;
    double x3 = x0 + h;

    double y1 = F(x1);
    double y2 = F(x2);
    double y3 = F(x3);

    if (y1 - 2 * y2 + y3 <= 0) {
        std::cerr << "Invalid argument.";
        return 0;
    }

    double zm;

    do {
        double z1 = x1 - x3;
        double z2 = x2 - x3;

        double p = ((y1 - y3) * z2 - (y2 - y3) * z1) / (z1 * z2 * (z1 - z2));
        double q = ((y1 - y3) * z2 * z2 - (y2 - y3) * z1 * z1) / (z1 * z2 * (z2 - z1));

        zm = -q / (2 * p);

        x1 = x2;
        x2 = x3;

        y1 = y2;
        y2 = y3;

        x3 = x3 + zm;

        y3 = F(x3);
    } while (fabs(zm) >= eps);

    return x3 + zm;
}

double F(double x)
{
    return pow(sin(x), 2) + cos(x); // !!!
}

int main() {
    // !!!
    std::cout << "Result: " << MP2(3, 0.1, 1e3, F) << std::endl;

    return 0;
}