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From: tanj@ucbvax.berkeley.edu
Newsgroups: net.unix-wizards
Subject: function parameters
Message-ID: <1703@brl-smoke.ARPA>
Date: Tue, 11-Mar-86 17:34:27 EST
Article-I.D.: brl-smok.1703
Posted: Tue Mar 11 17:34:27 1986
Date-Received: Fri, 14-Mar-86 06:48:03 EST
Sender: news@brl-smoke.ARPA
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I just spent an hour trying to figure out why my working program
suddenly stopped working.  Here's the culprit:

	    expand(*ptr++,*ptr++,*ptr++,ptr++,ptr++,ptr++);

(I'm working on a graphics project, which involves mapping surface
 textures to the surface of a torus {bagel}.  Expand takes a point
 and its norm and expands it to 16 more points by symmetry.)

After careful searching of K&R I found the reason;

	 The order of evaluation of arguments is undefined by the
	 language; take note that the various compilers differ.
							[p. 186]

The compiler I am using evaluates right to left.  If I were to number
the above arguments 1-6, when expand gets them they are 6-1.  I find
this contrary to my intuition.   Can anyone out there give me a good
reason as to why this is left up to compiler implementation?  And
if so is it generally true that evaluation of parameters is r-l?


			Sincerely,
				  Michael Berman
					(tanj@ucscc.BITNET)