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

double plgndr(double l, double m, double x)
{
	int ll,i;
	double pmm,somx2,fact,temp,pmmp1,pll;
    if( m < 0 || m > l || fabs(x) > 1.0)
		cout<<"bad arguments";
    pmm = 1.0;
    if (m > 0)
	{
        somx2 = sqrt((1.0 - x) * (1.0 + x));
        fact = 1.0;
        for( i = 1; i<=m; i++)
		{
            pmm = -pmm * fact * somx2;
            fact = fact + 2.0;
        }
    }
    if (l == m)
	{
        temp = pmm;
	}
    else
	{
        pmmp1 = x * (2 * m + 1) * pmm;
        if (l == m + 1)
		{
            temp = pmmp1;
		}
        else
		{
            for (ll = m + 2; ll<=l; ll++)
			{
                pll = x * (2 * ll - 1) * pmmp1 - (ll + m - 1) * pmm;
                pll = pll / (ll - m);
                pmm = pmmp1;
                pmmp1 = pll;
            }
            temp = pll;
        }
    }
	return temp;
}

void main()
{
    //program d4r31
    //driver for routine plgndr
    int i,j;
	char text[20];
    double nval,value,x,n,m,fac; 
    const double pi = 3.1415926;
    fstream fin;
    fin.open("d:\\vc常用數值算法集\\data\\fncval.dat",ios::in);
    while ( strcmp(text,"Legendre")!=0 )
	{
      fin>>text;
	}
	fin>>text;
    fin>>nval; 
    cout<<"Legendre Polynomials "<<endl;
    fin>>text;
    cout<<endl;
    cout<<"    n     m           x          actual       plgndr(n,b)"<<endl;
    for( i = 1; i<=nval; i++)
	{
		fin>>n;
		fin>>m;
        fin>>x;
		fin>>value;
        fac=1;
		if ( m > 0 )
		{
			for ( j= n - m + 1; j<=n+m; j++)
				fac = fac * j;
		}
        fac = 2 * fac / (2 * n+1 );
		value = value * sqrt(fac);
		cout<<setw(5)<<n;
		cout<<setw(6)<<m;
		cout<<setw(12)<<x;
        cout<<setw(17)<<value;
		cout<<setw(17)<<plgndr(n,m,x)<<endl;			          
    }
}