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Groups > comp.lang.java.programmer > #11219

Re: Curious compiler warning

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On 01/10/2012 11:50 PM, glen herrmannsfeldt wrote:
> Lew<noone@lewscanon.com>  wrote:
>
> (snip)
>
>>> (snip)
>>>>>      start--;
>>>>>      finish--;
>>>>>      bar(start, finish);
>>>
>
> (snip, then I wrote)
>>> Well, not thrown away until after the call to bar.
>
>> Irrelevant.  There's absolutely no value to storing the result because it
>> isn't reused.
>
>>> Does it actual notice that it isn't used other than the call to bar?
>
> (snip)
>> Apples and oranges.  The OP's example didn't reuse the stored value.
>> And yes, Eclipse would complain (but only if you enable it to do so)
>> because you are modifying a parameter, which is what the warning
>> cares about.
>
> One of the advantages of call by value is that you can use the parameter
> as a variable, and change it when needed.

All right.  A bit elliptical perhaps.  What are others, if that's "one of" them?

My comments about the OP's code were not to excoriate writing to parameters, 
but to excoriate writing to any variable to no purpose.

>> You could justify it perhaps in this case because you are using
>> the new value, unlike in the OP's example.  But then that's
>> a different scenario, so not relevant here.
>
>> And why does everyone insist on putting autodecrement on a
>> separate line anyway?
>
> It helps avoid the problem of using two on the same line.
>
> At least in C, you shouldn't do things like:
>
>   x=y[i++]+y[i++];
>
> I will guess that it isn't a good idea in Java, either.

Why isn't it a good idea in Java?

You may be right, but I'm curious why you think so.  The reasons would not be 
the same as for C, where the results are not well defined, since Java 
precisely defines the rules for such an expression.

> I wouldn't always put one on a separate line, but sometimes the
> extra readability is worth one or two lines.

Wha...?  The idioms in question were not two decrements of the same variable 
but one each of two different variables.

Take note of what you cited in your reply:
  start--;
  finish--;
  bar(start, finish);

Your comments are not germane to that case.

  bar(--start, --finish);

is just fine if you're going to reuse the stored decremented value.  But not 
if you're not.

-- 
Lew
Honi soit qui mal y pense.
http://upload.wikimedia.org/wikipedia/commons/c/cf/Friz.jpg

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Curious compiler warning Novice <novice@example..com> - 2012-01-11 01:51 +0000
  Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-10 18:10 -0800
    Re: Curious compiler warning glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-01-11 02:36 +0000
      Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-10 19:03 -0800
        Re: Curious compiler warning glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-01-11 07:50 +0000
          Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-10 23:57 -0800
        Re: Curious compiler warning Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-01-11 05:47 -0400
          Re: Curious compiler warning glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-01-11 13:25 +0000
            Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-11 06:58 -0800
              Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-11 07:01 -0800
              Re: Curious compiler warning Patricia Shanahan <pats@acm.org> - 2012-01-11 10:03 -0800
                Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-11 23:30 -0800
              Re: Curious compiler warning Gene Wirchenko <genew@ocis.net> - 2012-01-11 18:10 -0800
                Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-11 23:32 -0800
                Re: Curious compiler warning Leif Roar Moldskred <leifm@dimnakorr.com> - 2012-01-12 01:44 -0600
                Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-12 07:42 -0800
                Re: Curious compiler warning Leif Roar Moldskred <leifm@dimnakorr.com> - 2012-01-12 10:51 -0600
                Re: Curious compiler warning Patricia Shanahan <pats@acm.org> - 2012-01-12 07:50 -0800
                Re: Curious compiler warning Leif Roar Moldskred <leifm@dimnakorr.com> - 2012-01-12 10:54 -0600
                Re: Curious compiler warning Wanja Gayk <brixomatic@yahoo.com> - 2012-01-21 12:52 +0100
                Re: Curious compiler warning Gene Wirchenko <genew@ocis.net> - 2012-01-12 11:51 -0800
                Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-12 20:58 -0800
        Re: Curious compiler warning "Gavino" <invalid@invalid.invalid> - 2012-01-11 20:05 +0100
          Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-12 07:47 -0800
        Re: Curious compiler warning Wanja Gayk <brixomatic@yahoo.com> - 2012-01-21 12:52 +0100
          Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-21 12:13 -0800
    Re: Curious compiler warning Novice <novice@example..com> - 2012-01-11 04:55 +0000
      Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-10 21:46 -0800
      Re: Curious compiler warning glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-01-11 07:55 +0000
      Re: Curious compiler warning Roedy Green <see_website@mindprod.com.invalid> - 2012-01-11 01:35 -0800
        Re: Curious compiler warning "Gavino" <invalid@invalid.invalid> - 2012-01-11 20:05 +0100
          Re: Curious compiler warning Gene Wirchenko <genew@ocis.net> - 2012-01-11 18:18 -0800
            Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-12 07:55 -0800
              Re: Curious compiler warning Gene Wirchenko <genew@ocis.net> - 2012-01-12 11:59 -0800
            Re: Curious compiler warning Martin Gregorie <martin@address-in-sig.invalid> - 2012-01-13 00:02 +0000
              Re: Curious compiler warning Patricia Shanahan <pats@acm.org> - 2012-01-12 16:11 -0800
                Re: Curious compiler warning Martin Gregorie <martin@address-in-sig.invalid> - 2012-01-13 01:31 +0000
          Re: Curious compiler warning Roedy Green <see_website@mindprod.com.invalid> - 2012-01-11 18:26 -0800
            Re: Curious compiler warning Patricia Shanahan <pats@acm.org> - 2012-01-11 19:01 -0800
              Re: Curious compiler warning Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-01-11 23:23 -0500
                Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-12 08:00 -0800
            Re: Curious compiler warning Wanja Gayk <brixomatic@yahoo.com> - 2012-01-21 12:52 +0100
          Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-12 07:50 -0800
        Re: Curious compiler warning Gene Wirchenko <genew@ocis.net> - 2012-01-11 18:14 -0800
          Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-12 08:05 -0800
            Re: Curious compiler warning Gene Wirchenko <genew@ocis.net> - 2012-01-12 12:02 -0800
  Re: Curious compiler warning Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-01-10 21:11 -0500
    Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-10 18:17 -0800
    Re: Curious compiler warning bugbear <bugbear@trim_papermule.co.uk_trim> - 2012-01-11 16:10 +0000
    Re: Curious compiler warning Lars Enderin <lars.enderin@telia.com> - 2012-01-11 20:45 +0100
      Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-12 08:09 -0800
      Re: Curious compiler warning Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2012-01-12 18:14 +0200
      Re: Curious compiler warning Wanja Gayk <brixomatic@yahoo.com> - 2012-01-21 12:52 +0100
      Re: Curious compiler warning David Lamb <dalamb@cs.queensu.ca> - 2012-01-21 09:12 -0500
    Re: Curious compiler warning Gene Wirchenko <genew@ocis.net> - 2012-01-11 18:21 -0800
    Re: Curious compiler warning Lew <noone@lewscanon.com> - 2012-01-12 08:08 -0800
  Re: Eclipse 3.7.1 compiler warning v_borchert@despammed.com (Volker Borchert) - 2012-01-11 21:10 +0000

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