Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!eecae!netnews.upenn.edu!rutgers!cmcl2!adm!smoke!gwyn
From: gwyn@smoke.BRL.MIL (Doug Gwyn )
Newsgroups: comp.lang.c
Subject: Re: "for" loops
Message-ID: <9527@smoke.BRL.MIL>
Date: 28 Jan 89 04:35:49 GMT
References: <19579@agate.BERKELEY.EDU> <8515@lanl.gov>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 13

In article <8515@lanl.gov> jlg@lanl.gov (Jim Giles) writes:
>      for (x=0.0; x<=1.0, x+=0.1) {...}
>For a loop from 0.0 to 1000.0 by 0.01 on a 32-bit floating-point machine,
>the round-off of the last 100 adds is comparable to the increment itself!
>This may be another reason for the undesireable feature in C of assuming
>double precision as the default floating-point.

No, I don't think so.  I've never known anyone to recommend a loop
like the above.  The reasons for defaulting floating-point computations
to double precision in original C (no longer required in ANSI C) were
that it was easier to support on the PDP-11 that way and that numerical
applications were so rare in the UNIX C environment that the potential
loss of speed for such applications was not considered significant.