Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!quintus!ok
From: ok@quintus.UUCP (Richard A. O'Keefe)
Newsgroups: comp.lang.c
Subject: Re: How not to write a loop
Message-ID: <712@cresswell.quintus.UUCP>
Date: 29 Feb 88 23:02:43 GMT
References: <560@naucse.UUCP> <1988Feb11.200149.25172@sq.uucp> <2115@bsu-cs.UUCP> <832@unmvax.unm.edu>
Organization: Quintus Computer Systems, Mountain View, CA
Lines: 22
Keywords: For Loops Silliness Why

In article <832@unmvax.unm.edu>, mike@turing.UNM.EDU (Michael I. Bushnell) writes:
> I see NOTHING which precludes:
> 	float x;
> 	for (x = 0; x < 20; x += .5) printf("%f\n", x);
> The output would, of course, be
> 	0.0
> 	0.5
> 	...
> 	19.5

Quite right, there is nothing in K&R (or dpANS) to prohibit this.
But you have provided a good illustration of why people disparage
the use of floating-point variables in loop control.
THERE IS NO "OF COURSE" ABOUT THAT OUTPUT!

You should not be surprised to see as the last value
	19.99999
I just tried the very similar loop
	for (x = 0; x < 21; x += .3)	/* .3 divides 21 exactly */
By analogy with your "of course", the last output should obviously
be 20.7.  In fact, when I tried it just now, the last output was
	20.999994