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Re: confusion about behavior

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Todd Carnes <toddcarnes@gmail.com> writes:
> On Sun, 14 Aug 2011 12:06:19 -0700, Keith Thompson wrote:
>> LJ <djtheshowstopper@gmail.com> writes:
>>> int     a = 2;
>>> int     b = 3;
>>> c = a+++b;
>>> What will be the value of c??
>>> Shouldn't it be undefined depending upon the interpretation??
>> 
>> In a professional environment, the result will be "go back and fix the
>> code, then we'll look at it".
>> 
>> The assignment is equivalent to
>> 
>>     c = a++ + b;
>> 
>> due to the "maximal munch" rule (the same rule that makes "a+++++b" a
>> syntax error rather than "a++ + ++b").  The code is badly formatted and
>> difficult to read, but there is no ambiguity.
>> 
>> I'll assume that's enough to tell you what the code does.  If not, feel
>> free to ask.
>
> So, you're saying that it will first increment a by 1, then add the 
> result to b?

No, it's a post-increment.  The value of the expression `++a' is the
value of a *before* the increment, 2 (and, as a side effect, it sets a
to 3).

> What prevents it from being interpreted as a + ++b? Nevermind, I just 
> realized that you get the same result either way.

The "maximal munch" rule is what prevents it from being interpreted
as ``a + ++b''  And no, it wouldn't give you the same result; ``++b''
is a pre-increment, which means that result is the value of b *after*
incrementing it (4), which would change the value assigned to c.
It would also change which of a or b is affected by the increment.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Nokia
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

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confusion about behavior LJ <djtheshowstopper@gmail.com> - 2011-08-14 11:56 -0700
  Re: confusion about behavior China Blue Tip Wrench <chine.bleu@yahoo.com> - 2011-08-14 12:05 -0700
  Re: confusion about behavior Keith Thompson <kst-u@mib.org> - 2011-08-14 12:06 -0700
    Re: confusion about behavior Todd Carnes <toddcarnes@gmail.com> - 2011-08-15 01:57 +0000
      Re: confusion about behavior Keith Thompson <kst-u@mib.org> - 2011-08-14 19:10 -0700
        Re: confusion about behavior Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-08-15 03:44 +0100
          Re: confusion about behavior Keith Thompson <kst-u@mib.org> - 2011-08-14 20:27 -0700
      Re: confusion about behavior Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-08-14 22:52 -0400
      Re: confusion about behavior Seebs <usenet-nospam@seebs.net> - 2011-08-15 04:28 +0000
        Re: confusion about behavior Kenneth Brody <kenbrody@spamcop.net> - 2011-08-15 15:31 -0400
          Re: confusion about behavior Keith Thompson <kst-u@mib.org> - 2011-08-15 12:36 -0700
          Re: confusion about behavior Seebs <usenet-nospam@seebs.net> - 2011-08-15 20:33 +0000
            Re: confusion about behavior Kenneth Brody <kenbrody@spamcop.net> - 2011-08-16 14:39 -0400
              Re: confusion about behavior Keith Thompson <kst-u@mib.org> - 2011-08-16 12:27 -0700
                Re: confusion about behavior Willem <willem@toad.stack.nl> - 2011-08-16 19:47 +0000
      Re: confusion about behavior Barry Schwarz <schwarz45@yahoo.com> - 2011-09-05 04:50 -0700
        [OT] Re: confusion about behavior Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-09-05 09:07 -0400
        Re: confusion about behavior Kenneth Brody <kenbrody@spamcop.net> - 2011-09-06 12:42 -0400
  Re: confusion about behavior James Kuyper <jameskuyper@verizon.net> - 2011-08-14 15:10 -0400
    Re: confusion about behavior Todd Carnes <toddcarnes@gmail.com> - 2011-08-15 02:04 +0000
      Re: confusion about behavior Keith Thompson <kst-u@mib.org> - 2011-08-14 19:15 -0700
        Re: confusion about behavior Todd Carnes <toddcarnes@gmail.com> - 2011-08-15 02:34 +0000
      Re: confusion about behavior James Kuyper <jameskuyper@verizon.net> - 2011-08-14 22:37 -0400
    Re: confusion about behavior Todd Carnes <toddcarnes@gmail.com> - 2011-08-15 02:26 +0000

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