d2r7.cpp

Visual C++ 常用数值算法集 源代码

# include<iostream.h>
# include<math.h>
# include<iomanip.h>

void main()
{
    //program d2r7
    //driver for routine polcoe
    int nfunc,i,j,np = 5;
    double x,f,sum,xa[6], ya[6], coeff[6],pi = 3.141593;
    for (nfunc = 1; nfunc<=2; nfunc++)
	{
        if (nfunc == 1)
		{
            cout<<endl;
            cout<< "Sine function from 0 to pi"<<endl;
            for (i = 1; i<=np; i++)
			{
                xa[i] = i * pi /double( np);
                ya[i] = sin(xa[i]);
            }
		}
        else 
		{
			if (nfunc ==2)
			{
                cout<<endl;
                cout<< "Exponential function from 0 to 1"<<endl;
                for (i = 1; i<=np; i++)
				{
				    xa[i] = 1.0 * i / double(np);
				    ya[i] = exp(xa[i]);
				}
			}
            else
                return;
        }
        polcoe(xa, ya, np, coeff);
        cout<<"coefficients"<<endl;
        for (i = 1; i<=np; i++)
            cout<<setw(12)<<coeff[i];
		cout<<endl;
        cout<< "         x            f[x]       polynomial"<<endl;
		cout<<setprecision(6)<<setiosflags(ios::fixed);
        for (i = 1; i<=10; i++) 
		{
            if (nfunc == 1 )
			{
                x = (-0.05 + i / 10.0) * pi;
                f = sin(x);
			}
            else 
			{
				if (nfunc == 2)
				{
					x = (-0.05 + double(i) / 10.0);
					f = exp(x);
				}
            }
            sum = coeff[np];
            for (j = np - 1; j>=1; j--)
			{
				sum = coeff[j] + sum * x;
			}
            cout<<setw(14)<<x;
            cout<<setw(14)<<f;
            cout<<setw(14)<<sum<<endl;
		}
        cout<<  "**********************************"<<endl;
    }
}