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Re: A freshman's question

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Date	Thu, 20 Oct 2011 18:22:56 +0100
From	Patricia Shanahan <pats@acm.org>
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Subject	Re: A freshman's question
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Gene Wirchenko wrote:
> On Thu, 20 Oct 2011 07:30:31 -0700, Travers Naran <tnaran@gmail.com>
> wrote:
> 
> [snip]
> 
>> This is off topic, but I just recently learned that in C++, the result 
>> of i=i++ is officially undefined.  It's interesting a question related 
>> to what I learned comes up again in a completely different forum.
> 
>      That comes from C.  I have a question for anyone thinking it
> valid Java.  What is it supposed to do of use?  (If nothing, why even
> use it?)  I suspect the whole thing got started by someone not
> understanding that ++ causes an assignment to occur.

i = i++; is definitely valid Java, and actual compiler behavior matches
the results the JLS requires for it. Preventing it, but allowing any use 
of the i++ result would require some messy rules.

That does not mean it is a good idea.

In early C code, there was a tendency to try to stuff as much as
possible into a single expression. I don't know the causes - I suspect
some combination of macros and trying to avoid fetching a recently
calculated result from memory. Neither should be a concern in Java.

Patricia

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A freshman's question whl <wanghailunmail@gmail.com> - 2011-10-18 20:08 -0700
  Re: A freshman's question Patricia Shanahan <pats@acm.org> - 2011-10-19 04:48 +0100
    Re: A freshman's question whl <wanghailunmail@gmail.com> - 2011-10-19 00:54 -0700
      Re: A freshman's question Patricia Shanahan <pats@acm.org> - 2011-10-19 09:20 +0100
        Re: A freshman's question whl <wanghailunmail@gmail.com> - 2011-10-19 03:38 -0700
          Re: A freshman's question Lars Enderin <lars.enderin@telia.com> - 2011-10-19 17:48 +0200
            Re: A freshman's question Tim Slattery <Slattery_T@bls.gov> - 2011-10-19 12:24 -0400
              Re: A freshman's question whl <wanghailunmail@gmail.com> - 2011-10-20 03:55 -0700
            Re: A freshman's question whl <wanghailunmail@gmail.com> - 2011-10-20 03:50 -0700
          Re: A freshman's question Lew <lewbloch@gmail.com> - 2011-10-19 09:58 -0700
            Re: A freshman's question Patricia Shanahan <pats@acm.org> - 2011-10-19 18:47 +0100
            Re: A freshman's question whl <wanghailunmail@gmail.com> - 2011-10-20 03:48 -0700
        Re: A freshman's question whl <wanghailunmail@gmail.com> - 2011-10-19 03:49 -0700
          Re: A freshman's question Patricia Shanahan <pats@acm.org> - 2011-10-19 18:58 +0100
            Re: A freshman's question whl <wanghailunmail@gmail.com> - 2011-10-20 02:13 -0700
      Re: A freshman's question Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-10-19 06:05 -0300
        Re: A freshman's question whl <wanghailunmail@gmail.com> - 2011-10-19 03:38 -0700
    Re: A freshman's question Travers Naran <tnaran@gmail.com> - 2011-10-20 07:30 -0700
      Re: A freshman's question Gene Wirchenko <genew@ocis.net> - 2011-10-20 10:08 -0700
        Re: A freshman's question Patricia Shanahan <pats@acm.org> - 2011-10-20 18:22 +0100
        Re: A freshman's question Lew <lewbloch@gmail.com> - 2011-10-20 13:59 -0700
        Re: A freshman's question Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-10-20 17:38 -0500
  Re: A freshman's question Roedy Green <see_website@mindprod.com.invalid> - 2011-10-19 23:56 -0700
    Re: A freshman's question whl <wanghailunmail@gmail.com> - 2011-10-20 03:55 -0700

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