d5r7.cpp

C语言的编程合集！是我自己编的！很有用的！大家可以下载！有意见麻烦大家提出来以便本人及时修改！

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

double fder(double x)
{
    //derivative of func
	double aaa;
    aaa = 4.0 * x * ((x * x) - 1.0) * sin(x);
    return aaa + pow(x , 2) * ((x * x) - 2.0) * cos(x);
}

void chder(double a, double b, double c[], double cder[], int n)
{
	int j;
	double con;
    cder[n] = 0.0;
    cder[n - 1] = 2 * (n - 1) * c[n];
    if (n >= 3)
	{
        for (j = n - 2; j>=1; j--)
		{
            cder[j] = cder[j + 2] + 2 * j * c[j + 1];
        }
    }
    con = 2.0 / (b - a);
    for (j = 1; j<=n; j++)
	{
        cder[j]= cder[j] * con;
    }
}

double func(double x)
{
    return (x * x) * (x * x - 2.0) * sin(x);
}
void chebft(double a, double b, double c[], int n)
{
    int k,nmax = 50;
    double f[51];
    const double pi = 3.14159265358979;
	double bma,bpa,y,sum,fac;
    bma = 0.5 * (b - a);
    bpa = 0.5 * (b + a);
    for (k = 1; k<=n; k++)
	{
        y = cos(pi * (k - 0.5) / n);
        f[k] = func(y * bma + bpa);
    }
    fac = 2.0 / n;
    for (int j = 1; j<=n; j++)
	{
        sum = 0.0;
        for (k = 1; k<=n; k++)
		{
            sum = sum + f[k] * cos((pi * (j - 1)) * ((k - 0.5) / n));
        }
        c[j] = fac * sum;
    }
}

double chebev(double a, double b, double c[], int m, double x)
{
    if ((x - a) * (x - b) > 0.0)
	{
		cout<<"x not in range."<<endl;
	}
    double d = 0.0;
    double sv,y,y2,dd = 0.0;
    y = (2.0 * x - a - b) / (b - a);
    y2 = 2.0 * y;
    for (int j = m; j>=2; j--)
	{
        sv = d;
        d = y2 * d - dd + c[j];
        dd = sv;
    }
    return y * d - dd + 0.5 * c[1];
}

void main()
{
    //program d5r7
    //driver for routine chder
    int nval = 40;
    double a,b,x,aaa,pio2 = 1.5707963;
    double c[41], cder[41];
    a = -pio2;
    b = pio2;
    chebft(a, b, c, nval);
    //test derivative
    cout<<endl;
    cout<<"How many terms in chebyshev evaluation?"<<endl;
    //input mval , between 6 and 40, mval=0 to end
    int mval = 20;
    cout<<mval<<endl;
    if ((mval <= 0) || (mval > nval))
	{
		return;
	}
    chder(a, b, c, cder, mval);
    cout<<"        x          Actual     Cheby. deriv."<<endl;
	cout.setf(ios::fixed|ios::right);
	cout.precision(6);
    for (int i = -8; i<=8; i++)
	{
        x = i * pio2 / 10.0;
		cout.width(13);
        cout<<x;
		cout.width(13);
        cout<<fder(x);
        aaa = chebev(a, b, cder, mval, x);
		cout.width(13);
        cout<<aaa<<endl;
    }
}