#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

main(int argc, char *argv[])

{
    int i;
    double a,b,ab,fa,fb,fab;
    double tol;
    char *usage = "usage: %s [tolerance]\n";

    if(argc==1)  {
        tol = 0.001;
    }
    else if(argc==2)  {
        sscanf(argv[1], "%lf", &tol);
    }
    else  {
        fprintf(stderr, usage, argv[0]);
        exit(1);
    }

    a=3.0;
    b=3.5;
    i=0;
    printf("------------------------------------------------------------------------------------------------\n");
    printf("|iteration |           a |     (a+b)/2 |           b |        f(a) |        f(b) |  f((a+b)/2) |\n");
    printf("------------------------------------------------------------------------------------------------\n");
    while(fabs(b-a)>tol)  {
        i++;
        ab=(a+b)/2;
        fa=sin(a);
        fb=sin(b);
        fab=sin(ab);
        printf("|%8d: |%12.8lf |%12.8lf |%12.8lf |%12.8lf |%12.8lf |%12.8lf |\n", i,a,ab,b,fa,fab,fb);
        if(fa*fab<0)  b=ab;
        else if(fab*fb<0)  a=ab;
        else  { fprintf(stderr,"no zero in (%lf,%lf)\n",a,b); break; }
    }
    printf("------------------------------------------------------------------------------------------------\n");
    printf("zero of sin(x) found at %12.8lf in %d iterations (tolerance is %lf, exact value is %12.8lf)\n\n\n", ab,i,tol,M_PI);

    a=2.0;
    b=3.0;
    i=0;
    printf("------------------------------------------------------------------------------------------------\n");
    printf("|iteration |           a |     (a+b)/2 |           b |        f(a) |        f(b) |  f((a+b)/2) |\n");
    printf("------------------------------------------------------------------------------------------------\n");
    while(fabs(b-a)>tol)  {
        i++;
        ab=(a+b)/2;
        fa=pow(a,3.0)-11.0;
        fb=pow(b,3.0)-11.0;
        fab=pow(ab,3.0)-11.0;
        printf("|%8d: |%12.8lf |%12.8lf |%12.8lf |%12.8lf |%12.8lf |%12.8lf |\n", i,a,ab,b,fa,fab,fb);
        if(fa*fab<0)  b=ab;
        else if(fab*fb<0)  a=ab;
        else  { fprintf(stderr,"no zero in (%lf,%lf)\n",a,b); break; }
    }
    printf("------------------------------------------------------------------------------------------------\n");
    printf("zero of x^3-11 found at %12.8lf in %d iterations (tolerance is %lf, exact value is %12.8lf)\n", ab,i,tol,pow(11,1.0/3.0));
}