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From: rchrd@well.UUCP (Richard Friedman)
Newsgroups: comp.lang.fortran
Subject: Re: CDC FORTRAN trivia questions
Keywords: arithmetic if logical
Message-ID: <7622@well.UUCP>
Date: 10 Nov 88 18:09:20 GMT
References: <1196@helios.ee.lbl.gov> <3616@s.cc.purdue.edu> <7523@ut-emx.UUCP> <3622@s.cc.purdue.edu> <7693@boring.cwi.nl> <3627@s.cc.purdue.edu> <2183@tekcae.CAX.TEK.COM> <7588@well.UUCP> <7709@boring.cwi.nl>
Reply-To: rchrd@well.UUCP (Richard Friedman)
Organization: RCHRD 2855 Telegraph #415 Berkeley CA 94705
Lines: 21

In article <7709@boring.cwi.nl> dik@cwi.nl (Dik T. Winter) writes:
>                  floating-point and integer arithmetic do not generate -0,
>if the input operands do not contain -0.  But otherwise they can be generated.
>E.g. truncating a negative floating point value to integer (if between -1.0
>and 0.0).  Also overflowing integer multiply (which is really a special case
>of floating-point multiply) can return -0.  Most compilers compensate
>for this by adding +0 to the result, which turns -0 to +0.
>-- 
>dik t. winter, cwi, amsterdam, nederland

Yes, but the math library was written in COMPASS and early versions
were not very careful about propagating -0 thru sign extension under
special cases, usually resulting from scaling exponents.
In general the code compiled by FTN did a good job avoiding -0
but the library could not be trusted.


-- 
 ...Richard Friedman [rchrd]  Berkeley, CA.                         
    rchrd@well.uucp        -or-
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