Path: utzoo!utgpu!cunews!micor!latour!revcan!darren
From: darren@revcan.UUCP (Darren Morbey)
Newsgroups: comp.lang.c
Subject: The nonexistent ^^ operator
Summary: EVERYBODY SLOW DOWN PLEASE
Keywords: xor
Message-ID: <158@revcan.UUCP>
Date: 9 Apr 91 19:57:01 GMT
References: <156@revcan.UUCP>
Organization: Revenue Canada, Taxation; Office Communications Division
Lines: 39


Pardon me for interrupting (I started this whole thing in the first
place) but I've gotten a lot of email and posted articles about
the bitwise xor.  Unfortunately, our system has been down for
several days, so the article I planned to post, including your
comments and suggestions, will need _major_ rewriting to accomodate
all comments.  I _will_ post some of the comments I have recieved
as well as other macros.  Thanks to you all for sending.

I believe my request should be revised, however, regarding some
of the points made in these articles.  In light of them, I revise
what I require here:

I would like to "simulate" ^^ i.e if( a ^^ b ) with a macro thus:
      #define XOR(A,B) ...
The macro should accept all numeric types for A and B, treating them
as "0" or "non-0" as && and ||.  If a macro is supplied, each operand
must be evaluated O&OO (once and only once.)

There are some things I knew and that I didn't know that I would like
to make clear that I know them now.  They are as follows:
I KNEW there is no short-circuit evaluation for XOR as there is for
  && and ||.  I want to guarantee that they are both executed anyway.
I DIDN'T KNOW && and || short circuited.
I DIDN'T KNOW !(a) is always an int.
I DIDN'T KNOW A?B:C means only one of B and C are evaluated.
I JUST REALIZED for certain A and B, my #1 could execute A _twice_
  and B _not_ _at_ _all!_
I DID KNOW that #1 is unsatisfactory.  It was put on as a general idea.
  Please no more about it, but I do challenge anyone who can figure
  out how my last statement is possible.  I will post the answer later.
  Other than that, please don't flog my dead horse.  :-)

Thank you again for your comments.  It will take a while to summarize
everything I have recieved.  Until then, happy programming.

[ Darren Morby     +1 613 957 9281     {uunet|lsuc|fts1}!revcan!darren ]
[ Revenue Canada Taxation, 3052-400 Cumberland St, Ottawa,ONT  K1A 0L8 ]
[ "The challenge... is yours."                             -Dick Clark ]