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Full Discussion: Confusion with ++ operator
Top Forums UNIX for Dummies Questions & Answers Confusion with ++ operator Post 302914249 by Don Cragun on Saturday 23rd of August 2014 04:19:52 PM
Old 08-23-2014
Quote:
Originally Posted by Abhishek_kumar
Can anyone guide me whats happening in this program given below. I got the Output 7 7 12 49... i was expecting 5 16 9 25.
First is simple (3+1)*(3+1)
Second is again 3*3; i =4 now
Third i =5 then 5*5;
i don't know where i am going wrong!
Code:
#include<stdio.h>
#define PRODUCT(x) (x*x)
int main()
{
	int i=3,j,k,l;
	j=PRODUCT(i+1);
	k=PRODUCT(i++);
	l=PRODUCT(++i);
	printf("%d %d %d %d\n",i,j,k,l);	
	return 0;
	
}

There is a big difference between a macro expansion and a function call. Your assignments to j, k, and l expand to:
Code:
	j=i+1*i+1; /* 3 + 3 + 1 -> 7 */
	k=i++*i++; /* 3 * 4 -> 12 leaving i set to 5 */
	l=++i*++i; /* 6 * 7 -> 42 leaving i set to 7 */

Are you sure you got 49 instead of 42 as the last number printed?
 

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update-rcconf-guide

UPDATE-RCCONF-GUIDE(8)						 Debian GNU/Linux					    UPDATE-RCCONF-GUIDE(8)

NAME

       update-rcconf-guide - Create default guide file for rcconf

SYNOPSIS

       update-rcconf-guide

DESCRIPTION

       Update-rcconf-guide creates the default guide file which rcconf uses.

       Update-rcconf-guide searches the package names corresponding to each service file in /etc/init.d directory from dpkg info
       files(/var/lib/dpkg/info/*.list) and get the description of these packages using apt-cache. Update-rcconf-guide uses Short-Description in
       priority to the description if service files has Short-Description field.  Update-rcconf-guide writes those results to
       /var/lib/rcconf/guide.default file.

       You can write your own guide in user guide file(/var/lib/rcconf/guide) by hand.	Rcconf refers Guides in /var/lib/rcconf/guide before those
       in /var/lib/rcconf/guide.default.

       If you install some packages after executed update-rcconf-guide, you need to re-create this file using update-rcconf-guide so as to refresh
       guide.default that includes new guides for installed new services.

       Notice: update-rcconf-guide was not executed when you installed rcconf
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FILE

       /var/lib/rcconf/guide.default
	       Guide File update-rcconf-guide generates.

       /var/lib/rcconf/guide
	       Guide File user(Administrator) can define.

SEE ALSO

       rcconf(8)

AUTHOR

       Atsushi KAMOSHIDA <kamop@debian.org>

perl v5.10.1							    2009-01-21						    UPDATE-RCCONF-GUIDE(8)
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