Path: utzoo!yunexus!geac!syntron!jtsv16!uunet!mcvax!dik
From: dik@cwi.nl (Dik T. Winter)
Newsgroups: comp.lang.fortran
Subject: Re: CDC FORTRAN trivia questions
Keywords: arithmetic if logical
Message-ID: <7694@boring.cwi.nl>
Date: 1 Nov 88 23:16:24 GMT
Article-I.D.: boring.7694
References: <1196@helios.ee.lbl.gov> <3616@s.cc.purdue.edu> <7691@boring.cwi.nl> <3624@s.cc.purdue.edu>
Organization: CWI, Amsterdam
Lines: 30

In article <3624@s.cc.purdue.edu> ags@s.cc.purdue.edu.UUCP (Dave Seaman) writes:
 > In article <7691@boring.cwi.nl> dik@cwi.nl (Dik T. Winter) writes:
 > >Beware, .FALSE. is +0;  truth values returned by expressions could have any
 > >arithmetic value with negative for .TRUE. and positive for .FALSE..
 > >So -0 is .TRUE. (yes, it is a 1-s complement machine).
 > 
 > 	print 10, .true., .false.
 >      10 format(2(1x,o20))
 > 	end
 > 
 > for which the output was:
 > 
 >  77777777777777777776 00000000000000000000
You missed something: I wrote: the constant .TRUE. is -1 indeed, but a logical
expression could very well return -0 for .TRUE..
Try:
	logical function equal(i,j)
	equal = i.eq.j
	return
	end
	print 10, equal(1,1)
	10 format(1x,o20)
	end
the output is:
	77777777777777777777
(yes, -0).  (It might depend on the level of optimisation.)
-- 
dik t. winter, cwi, amsterdam, nederland
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