/*	prog1a.c -- Determine Machine Epsilon
	Written Sep 20, 2002 by Eric Olson for Mathematics 483

	For more information see Step 3 in First Steps in Numerical
	Analysis, 2nd Edition, by Hosking, Joe, Joyce and Turner */

#include <stdio.h>
#include <math.h>
#define REAL double

REAL maxdelta(REAL x){
	REAL a,b,delta,deold,r1;
	a=0.0;
	if(x>0.0) b=x; 
	else b=-x;
	deold=a;
	for(;;){
		delta=(a+b)/2.0;
		if(deold==delta) break;
		r1=x+delta;
		if(r1==x) a=delta;
		else b=delta;
		deold=delta;
	}
	return a;
}

REAL data[] = { 1.0, 2.0, 3.0, 4.0, 5.0, 10.0, 100.0, 1000.0 };

main(){
	int i;
	REAL x,delta;
	printf("prog1a.c -- Determine Machine Epsilon\n\n");
	printf("Using %d byte floating point.\n\n", sizeof(REAL));
	for(i=0;i<sizeof(data)/sizeof(REAL);i++){
		x=data[i];
		delta=maxdelta(x);
		printf("x=%g delta=%g\n",x,delta);
	}
}