Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!ames!oliveb!sun!rushforth!kcr
From: kcr%rushforth@Sun.COM (Kevin Rushforth)
Newsgroups: comp.sys.mac.programmer
Subject: Re: LSC arithmetic problem
Message-ID: <100903@sun.Eng.Sun.COM>
Date: 25 Apr 89 01:06:04 GMT
References: <1837@etive.ed.ac.uk>
Sender: news@sun.Eng.Sun.COM
Reply-To: kcr@sun.UUCP (Kevin Rushforth)
Organization: Sun Microsystems, Mountain View
Lines: 25

In article <1837@etive.ed.ac.uk> nick@lfcs.ed.ac.uk (Nick Rothwell) writes:
>Well, perhaps not a problem, but certainly a "gotcha". The following
>declaration:
>
>	long L = (1<<16) + 1;
>
>results in L being (long) 1. Presumably LSC does its intermediate arithmetic
>in 16-bit ints

K&R and the proposed ANSI standard both say that integer arithmetic is
done in "int" precision (whatever that may be for your machine) unless
one or more of the operands is of type long.  On a MAC, the LSC
compiler uses 16-bit ints (don't know about the MPW compiler).  To
ensure that the calculations are done in "long" precision (i.e. 32-bit
arithmetic), you can do what you suggested (cast the constant(s) to
long) or more simply declare the constants as long in the first place:

	long L = (1L << 16) + 1L;

-- 
Kevin C. Rushforth                   | "If winning is not important,
Sun Microsystems                     |  then commander, why keep score?"
                                     |              - Lt. Worf
ARPA: kcr@sun.com                    |
UUCP: <most-backbone-sites>!sun!kcr  |