求解常微分方程初值問題之多步Euler預報-校正法

//實現多步Euler法
#include <iostream>
#include <math.h>
#include <iomanip>

using namespace std;

class multi_euler
{
private:
 int i, n;
 double f, h, x, x_last, yc, yc_old, yp;

public:
 double func(double z, double t)
 {
  f = -0.3 * pow((t - 50), 1.25);
  return f;
 }
 void pc();
};

void main()
{
 multi_euler multistep_pc;
 multistep_pc.pc();
}

void multi_euler::pc()
{
 cout << "\n輸入初始條件：" << endl;
 cout << "\n輸入x0：";
 cin >> x;
 cout << "\n輸入y0：";
 cin >> yc;
 cout << "\n輸入y(-1)：";
 cin >> yc_old;
 cout << "\n輸入y需要的x值：";
 cin >> x_last;
 cout << "\n輸入等分數：";
 cin >> n;
 h = (x_last - x) / n;
 cout.precision(7);
 for (i = 0; i < n; i++)
 {
  yp = yc_old + 2 * h * func(x, yc);
  yc_old = yc;
  yc += 0.5 * h * (func(x, yc) + func((x + h), yp));
  x += h;
  cout << x << setw(12) << yc << endl;
 }
}