d4r01.cpp

此代码为VC++常用数值算法这本书中附赠的光D部分的源代码

#include <iostream.h>
#include <math.h>
#include <iomanip.h>
#include <stdlib.h>
#include <fstream.h>
#include <string>

void main()
{
    //program d4r1
    //driver for routine gammln
	int nval,i;
	char text[20];
    double calc,x,actual; 
    const double pi = 3.1415926;
    fstream fin;
    fin.open("d:\\vc常用数值算法集\\data\\fncval.dat",ios::in);
    while (strcmp(text,"Gamma")!=0)
	{
      fin>>text;
	}
    fin>>text;
	fin>>nval;	fin>>text;
    cout<<"Log of Gamma function"<<endl;
    cout<<endl;
    cout<<"      x          actual         gamma(x)"<<endl;
    for( i = 1; i<=nval; i++)
	{
        fin>>x;
		fin>>actual;
        if (x > 0.0)
		{
            if (x >= 1.0)
			{
                calc = gammln(x);
			}
            else 
			{
                calc = gammln(x + 1) - log(x);
			}
			cout<<setprecision(1)<<setiosflags(ios::fixed);
            cout<<setw(8)<<x;
			cout<<setprecision(6);
            cout<<setw(16)<<log(actual);
            cout<<setw(16)<<calc<<endl;
        }
    }
}