/*************************    Program 2.7    ****************************/
/*                                                                      */
/************************************************************************/
/* Please Note:                                                         */
/*                                                                      */
/* (1) This computer program is written by Tao Pang in conjunction with */
/*     his book, "An Introduction to Computational Physics," published  */
/*     by Cambridge University Press in 1997.                           */
/*                                                                      */
/* (2) No warranties, express or implied, are made for this program.    */
/*                                                                      */
/************************************************************************/

# include <stdio.h>
# include <math.h>
# define f(x) (exp(x)*log(x)-x*x)

main()
/* Root of f(x)=0 with the bisection method.
   Copyright (c) Tao Pang 1997. */
{
int istep;
double dl=1e-6;
double a,b,x0,dx;

a = 1.0; b = 2.0;
dx = b-a;
istep = 0;
while (fabs(dx) > dl)
  {
  x0 = (a+b)/2.0;
  if ((f(a)*f(x0))<0)
    {
    b  = x0;
    dx = b-a;
    }
  else
    {
    a  = x0;
    dx = b-a;
    }
    istep = istep+1;
  }
    printf("%4d %16.8lf %16.8lf\n", istep,x0,dx);
}