#include <iostream>
#include <iomanip>
#include "quanc8.c"
#include "spline.c"

const int N = 7;
double resultArray[N];
double resultArray2[N-1];
double pointArray[N];
const double h = 0.2;
const double A = 1;
const double lowX = 1.5;
const double topX = 2.7;
double EA = 0;
double ER = 0;
double RESULT = 0;
double ERR = 0;
int    NOFUN = 0;
double POSNR = 0;
int    FLAG = 0;

double FUN(double t)
{
    return  sin(t) * sin(t);
}

double lagrange8(double resultArray[N], double pointArray[N], double x)
{
    double res = 0;
    for (int i = 0; i < N-1; i++)
    {
        double chislitel = 1;
        double znamenatel = 1;
        for (int j = 0; j < N-1; j++)
        {
            if (j != i)
            {
                chislitel *= x - pointArray[j];
                znamenatel *= pointArray[i] - pointArray[j];
            }
        }
        res += (resultArray[i] * chislitel) / znamenatel;
    }
    return res;
}

int main()
{
    int j = 0;
    for (double i = lowX; i <= topX; i += h)
    {
        quanc8(*FUN, A, i, EA, ER, &RESULT, &ERR, &NOFUN, &POSNR, &FLAG);
        pointArray[j] = i;
        resultArray[j++] = RESULT;
        std::cout << std::setw(4) << i << "  " << RESULT << '\n';
    }
    std::cout << '\n';

    int last = 0;
    const double x0 = 1.6;

    for (int k = 0; k <= 5; k++)
    {
        quanc8(*FUN, A, x0 + h * k, EA, ER, &RESULT, &ERR, &NOFUN, &POSNR, &FLAG);
        resultArray2[k] = RESULT;
        std::cout << x0 + h * k << " :   " << RESULT << '\n';
    }
    std::cout << '\n';
    std::cout << "             Lagrange" << "       Spline" << '\n';
    double b[N];
    double c[N];
    double d[N];
    spline(N, 0, 0, resultArray[0], resultArray[N - 1], pointArray, resultArray, b, c, d, &FLAG);

    for (int k = 0; k <= 5; k++)
    {
        quanc8(*FUN, A, x0 + h * k, EA, ER, &RESULT, &ERR, &NOFUN, &POSNR, &FLAG);
        resultArray2[k] = RESULT;
    }

    for (int k = 0; k <= 5; k++)
    {
        double lagrangeResult = lagrange8(resultArray, pointArray, x0 + h * k);
        double splineResult = seval(N, x0 + h * k, pointArray, resultArray, b, c, d, &last);
        std::cout << "x = " << x0 + h * k << ":  " << std::setw(8) << lagrangeResult << "    " << std::setw(8) <<splineResult << " | EPS_Lagrange = " << std::setw(8) << resultArray2[k] - lagrangeResult << "  EPS_Spline = " << resultArray2[k] - splineResult << '\n';
    }
}