Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!ucbvax!ucsfcgl!conrad
From: conrad@cgl.ucsf.edu (Conrad Huang)
Newsgroups: comp.sys.sgi
Subject: Re: IRIX 3.2 C compiler bug
Message-ID: <12999@cgl.ucsf.EDU>
Date: 5 Feb 90 18:40:44 GMT
References: <90Feb5.000622est.4918@neat.cs.toronto.edu> <13583@phoenix.Princeton.EDU>
Sender: daemon@cgl.ucsf.edu
Lines: 39

>>On a 4D/240S running 3.2:
>>	% cat t.c
>>	main()
>>	{
>>		double a,b,c;
>>
>>		b = 1.0;
>>		c = 2.0;
>>		a = b==c;
>>		printf("a=%f\n",a);
>>	}
>>	% cc t.c
>>	% ./a.out
>>	a=2147469288.000000
>Just what did you expect this to return?  Unless I am mistaken, ANSI C 
>still doesn't any distinction about what number is returned, only that 
>it is NOT zero, which is certainly the case for your code here.  It is probably
>also true that comparison of floating point numbers is an inherently dicey
>proposition.  

Say what!?  In K&R, Appendix A, page 189, Section 7.6,

	"The operators < (less than), > (greater than), <= (less than or
	equal to) and >= (greater than or equal to) all yield 0 if the
	spricified relation is false, and 1 if it is true"

and on page 190, Section 7.7,

	"The == (equal to) and the != (not equal to) operators are exactly
	analogous to the relation operators except for their lower precedence."

Please tell me if ANSI C has revoked these statements!

So...

In the first place, the program ought to print 0, since 1.0 == 2.0 is *false*.
In the second place, even if they were equal, it should print 1.000000.

Conrad