?? d14r3.cpp
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#include <iostream.h>
#include <math.h>
#include <iomanip.h>
#include <stdlib.h>
#include <fstream.h>
#include <string>
#include <process.h>
void derivs(double x, double y[],double dydx[])
{
dydx[1] = -y[2];
dydx[2] = y[1] - (1.0 / x) * y[2];
dydx[3] = y[2] - (2.0 / x) * y[3];
dydx[4] = y[3] - (3.0 / x) * y[4];
}
void main()
{
//program d14r3
//driver for routine rkqc
int n,i;
double y[5], dydx[5], yscal[5],x,htry,eps,hdid,hnext;
n = 4;
x = 1.0;
hnext=0.0;
hdid=0.0;
eps=0.0;
y[1] = bessj0(x);
y[2] = bessj1(x);
y[3] = bessj(2, x);
y[4] = bessj(3, x);
dydx[1] = -y[2];
dydx[2] = y[1] - y[2];
dydx[3] = y[2] - 2.0 * y[3];
dydx[4] = y[3] - 3.0 * y[4];
for (i = 1; i<=n; i++)
{
yscal[i] = 1.0;
}
htry = 0.1;
cout<<endl;
cout<<" eps htry hdid hnext"<<endl;
cout<<setiosflags(ios::fixed);
for( i = 1; i<=15; i++)
{
eps = exp(-float(i));
rkqc(y, dydx, n, x, htry, eps, yscal, hdid, hnext);
cout<<setprecision(7)<<setw(12)<<eps;
cout<<setprecision(6)<<setw(13)<<htry;
cout<<setprecision(6)<<setw(13)<<hdid;
cout<<setprecision(6)<<setw(13)<<hnext<<endl;
}
}
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