d3r7.cpp

来自「工程算法 这是一个很有用的工程数值算法集锦」· C++ 代码 · 共 34 行

#include "iostream.h"
#include "math.h"

double func(double x)
{
    return x * exp(-x);
}

void main()
{
    //program d3r7
    //driver for routine qgaus
    double x,ss,aaa,dx, x1 = 0.0;
    double x2 = 5.0;
    int nval = 10;
    dx = (x2 - x1) /(double)nval;
    cout<<endl;
    cout<<"    0.0to          qgaus        expected"<<endl;
	cout.setf(ios::fixed|ios::right);
	for (int i = 1; i<=nval; i++)
	{
        x = x1 + (double)i * dx;
        qgaus(x1, x, ss);
        cout<<"    "<<x;
		cout.precision(6);
		cout.width(14);
        cout<<ss;
        aaa = -(1.0 + x) * exp(-x) + (1.0 + x1) * exp(-x1);
		cout.width(14);
        cout<<aaa<<endl;
    }
}