Ira 4m lab1

// Ira_4m.cpp: определяет точку входа для консольного приложения.
//

#include "stdafx.h" //for visual studio 2010

#include <iostream>
#include <cstdio>
#include <vector>
#include "gnuplot_i.hpp"
#include <conio.h>
#include <windows.h>

#define cyrillic setlocale(LC_CTYPE, "rus")

using namespace std;

char* p;

double f(double x);
string parse_path(char* path);
void concat(vector<char> & v , string s);

double trapezoidal_rule(double a , double b , int n){
    double h = (b - a) / n;
    double sum = 0.0;
    for(int i = 0 ; i < n ; ++i){
        double x = a + h * double(i);
        double xx = a + h * double(i + 1);
        sum += f(x) + f(xx);
    }
    sum *= h;
    sum /= 2.0;
    return sum;
}

double simpson(double a , double b , int n){
    double h = (b - a) / n;
    double sum = 0.0;
    for(int i = 1 ; i < n ; ++i){
        double x = a + h * (double)i;
        int c = 2 + 2 * (i % 2);
        sum += (double)c * f(x);
    }
    sum += f(a) + f(b);
    sum *= h;
    sum /= 3.;
    return sum;
}

double rectangle_method(double a , double b , int n){
    double h = (b - a) / n;
    double sum = 0.0;
    for(int i = 0 ; i < n ; ++i){
        double x = a + h * (double)i;
        sum += f(0.5 * (x + x + h));
    }
    return h * sum;
}

void plot(double a , double b , int n , double (*method)(double a , double b , int n) , string head){
    string parse_p = parse_path(p);
    vector<char> path(parse_p.begin() , parse_p.end());
    path.push_back('\0');
    concat(path , "temp.txt");

    double h = (b - a) / n;

    vector<pair<double , double>> segments;
    segments.push_back(make_pair(a , 0.));

    for(int i = 1 ; i <= n ; ++i){
        double x = a + h * (double)i;
        double xx = a + h * (double)(i - 1);
        double segans = method(xx , x , 100);
        segments.push_back(make_pair(x , segans));
        segments[segments.size() - 1].second += segments[segments.size() - 2].second;
    }

    FILE * file = fopen(&path[0] , "w");
    fprintf(file , "# X   Y\n");
    for(int i = 0 ; i < segments.size() ; ++i){
        fprintf(file , "  %lf   %lf\n" , segments[i].first , segments[i].second);
    }
    fclose(file);

    Gnuplot gnu("lines");
    string fi = "set style line 1 lc rgb '#0060ad' lt 2 lw 2 pt 0 ps 1.5";
    string se = &path[0]; se = "plot '" + se; se += "' with linespoints ls 1";

    gnu.set_grid();
    gnu.set_title(head);
    gnu.plot_points(se , fi);

    FlushConsoleInputBuffer(GetStdHandle(STD_INPUT_HANDLE));
    cout << endl << "Press any key to continue..." << endl;
    _getch();

    gnu.remove_tmpfiles();
    remove(&path[0]);
}


double f(double x){
    return x * x;
}


int main(int argc , char* argv[]){
    cout.precision(10);
    cout.setf(ios::fixed);
    cyrillic;


    p = argv[0];

    double a , b;
    int n;
    cin >> a >> b >> n;

    cout << "Метод трапеций: " << trapezoidal_rule(a , b , n) << endl;

    cout << "Формула Симпсона: " << simpson(a , b , n) << endl;

    cout << "Метод средних прямоугольников: " << rectangle_method(a , b , n) << endl;

    plot(a , b , n , &trapezoidal_rule , "График методом трапеций");

    plot(a , b , n , &simpson , "График формулой Симпсона");

    plot(a , b , n , &rectangle_method , "График методом средних прямоугольников");

    system("pause");

    return 0;
}

string parse_path(char* path){
    string s = path;
    size_t pos = s.find_last_of('\\');
    if(pos != string::npos){
        return s.substr(0 , pos + 1);
    }
    if(s[s.size() - 1] != '\\')s += '\\';
    return s;
}

void concat(vector<char> & v , string s){
    v.pop_back();
    for(int i = 0 ; i < s.size() ; ++i){
        v.push_back(s[i]);
    }
    v.push_back('\0');
}