Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!ucbarpa.Berkeley.EDU!klier
From: klier@ucbarpa.Berkeley.EDU (Pete Klier)
Newsgroups: comp.lang.c
Subject: Re: programming puzzle (silly)
Summary: 88 char portable solution
Message-ID: <28336@ucbvax.BERKELEY.EDU>
Date: 10 Mar 89 02:04:48 GMT
Sender: usenet@ucbvax.BERKELEY.EDU
Lines: 17


***********************
main(m,n){scanf("%d",&n);for(m=n>0^n>9;n&&m*=n--;);
printf(m?"Answer=%d\n":"error\n",m);}
***********************

with help from Jeff Conroy (jmconroy@ernie.Berkeley.EDU)
 
the expression "m=n>0^n>9" is equivalent to 
"m = (n > 0) && (n <= 9)" (check it out)
so "m" is 1 (initially) iff n is within range, 0 otherwise.
If m is 0 in the body of the loop, then the expression
(n&&m*=n--) is 0, since (m*=n--) is 0.  Otherwise, we
have an ordinary factorial loop, which begins with
m == 1.  
Pete Klier
klier@ernie.Berkeley.EDU