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From: mrd@sun.mcs.clarkson.EDU (Michael R. DeCorte)
Newsgroups: comp.lang.c
Subject: Possible C Anomaly
Message-ID: <9270@brl-adm.ARPA>
Date: Mon, 14-Sep-87 11:56:12 EDT
Article-I.D.: brl-adm.9270
Posted: Mon Sep 14 11:56:12 1987
Date-Received: Tue, 15-Sep-87 05:41:57 EDT
Sender: news@brl-adm.ARPA
Lines: 35


		   .
   /* Example #1 */            k = (k > 1) ? k-- : 1;

   My intent was to decrement k with each pass until it reached 1 and then to
   keep it at one.  There are a variety of ways to accomplish this but I just
   happened to try this one first.

   The problem is is that the two examples behave differently.  In the first
   example k does not change values.  It remains equal to 10 indefinitely.

Try 
	k = (k > 1) ? --k : 1;
or
	k = (k > 1) ? (k - 1) : 1;

from page 42 of KR

"But the expression ++n increments n before using its value, while n++
increments n after its values has been used."

You will also notice the chart on page 49 in section 2.12 Precedence
and Order of Evaluation

for the expression 
	k = (k > 1) ? k-- : 1;
	1    2        3

the compiler evaluates the  k(3) yielding an rvalue. It then decrements
the lvalue k.  It then assign to the lvalue k(1) the rvalue generated
by k(3).  As k(3) was equal to k you have an infinite loop.  This
what is supposed to happen. 

Michael DeCorte
mrd@clutx.clarkson.edu