I'm disappointed $a+++++$a doesn't work as expected :(
On 20 July 2013 06:08, Sherif Ramadan <theanomaly...@gmail.com> wrote: > Sara, > > On Sat, Jul 20, 2013 at 12:44 AM, Sara Golemon <poll...@php.net> wrote: > > > What's undefined isn't the relationship between preinc/postinc and add. > > What's undefined is the use of multiple preinc/postinc operators within > a > > single expression > > > > I'm sorry but I can not find any evidence of how that is undefined. The > operators are right-associative, with a defined level or precedence. Their > operands are well defined and their return value in the expression is > determined by the compiler, not the parser. In this sense the compiler > always executes those opcodes first and returns a temporary variable. > > > > (preincrements in particular). Our parser grammer, as it currently > > stands, does have a predictable order, but that is a side-effect of > > implementation. The language's definition of order of resolution of > > multiple preinc/postinc elements within a single ticked statement is that > > they are undefined. And *that* is what made your *particular* change to > > the documentation incorrect. > > > > The parser grammar in general is pretty muddled, I will agree with that. > However, the precedence order here is well defined within the expression. I > can not see any condition under which the compiler will introduce > unpredictable order of these opcodes or their results. > > > > > > If you'd like to define behavior for: echo ++$a + 1; then that's a > > different matter. Defining the behavior of ++$a + $a++, however is > > inviting misunderstanding*. > > > > What was inappropriate, was asking for comment, receiving comment which > > cited an issue, then committing without discussing that issue first. > > > > -Sara > > > > * Even if, technically, either order of evaluation will result in the > same > > answer for this contrived expression. ++$a * $a++ is a more obviously > > ambiguous answer for a language which explicitly does not define an order > > of resolution. > > > > By that logic we should indicate that -$a * $a is also undefined behavior? > I know the parser grammar is not well-defined and I'm taking this fact into > consideration, but here we are talking about operators which will compile > down into very much well-defined opcodes and have a predictable order of > resolution. It's quite possible that someone could introduce a change later > on that will cause a different result, but the likelihood of that becoming > a reality is slim-to-none. > > I'm not a fan of getting into cat and mouse games over these types of > discussions, however. I posed my opinion on this matter and I refuse to > overwrite someone's commit because I feel my opinion is the only one that > counts. I am certainly not above being wrong. I just want to be sensible. > > > > > > > > On Fri, Jul 19, 2013 at 9:28 PM, Yasuo Ohgaki <yohg...@ohgaki.net> > wrote: > > > >> Hi Sara, > >> > >> 2013/7/20 Sara Golemon <poll...@php.net> > >> > >>> On Fri, Jul 19, 2013 at 7:16 PM, Yasuo Ohgaki <yohg...@ohgaki.net > >wrote: > >>> > >>>> > >>>> > >>>> If there aren't comments, I'll rewrite the example. > >>>> > >>>> > >>>> There were comments. I explicitly told you that that the behavior is > >>> defined as undefined. You CHOSE to ignore that comment. You CHOSE to > >>> break the documentation. > >>> > >> > >> If there is defined precedence, arithmetic operation should follow it. > >> If there is exception, it should be documented. > >> > >> I don't understand why/how the arithmetic operation can be > >> ambiguous with defined precedence. (++ and -- are higher than +) > >> > >> $a = 1; > >> echo ++$a + $a++; > >> > >> should always print 4 with current PHP precedence definition. > >> If it does not, it's a bug in language. > >> > >> // mixing ++ and + produces undefined behavior > >> $a = 1; > >> echo ++$a + $a++; // may print 4 or 5 > >> > >> I don't see any reason it became undefined. > >> If this kind of simple precedence is broken, how programmers write > >> code and/or trust the language? > >> > >> http://3v4l.org/mR4da/vld#tabs > >> > >> This site seems support PHP 4.3.0 to PHP 5.5.0 and opcode looks > >> fine. Am I missing something? > >> > >> If you would like to suggest use of (), it should be done differently. > >> IMHO. > >> The comment only ruins PHP's reputation as language. > >> > >> Regards, > >> > >> -- > >> Yasuo Ohgaki > >> yohg...@ohgaki.net > >> > > > > >
