Talk:Operators in C and C++

message: came here looking for the exponentiation operator, did not find.  Apparently there isn't one, so I shall do it with bit munging.  A note here to the effect that one must use a function for exponentiation would improve the value of this page as a reference.  —Preceding unsigned comment added by 108.16.83.48 (talk) 20:15, 27 January 2011 (UTC)
thread_title: exponentiation operator?

message: The prototype column horribly esoteric.  It needs its own explanation.
--
I agree that it's esoteric, but I don't think it needs explanation: the whole column needs to be removed completely. It's completely redundant.
I think its content is highly inappropriate for Wikipedia, and if you're looking for more useful information (like what the h-ll the operators actually mean), you'll end up using Google, anyway.
Similar to the comment below, I suggest that we replace the prototype column with another column that briefly describes what the operator actually does.
121.210.170.141 (talk) 06:40, 19 November 2009 (UTC)
thread_title: Prototypes

message: Hi. I wonder if it might be useful to describe what some of these operators do. I'm not familiar, for example, with the comma (',') operator, and it would be neat to know what it does.
Well, it is hard to put that stuff in the table, but I agree it would be nice to have links or something. For what it is worth though, the comma operator is not very important. The most common place it is used is in for statements, for ( ix=0, jx=0; ix < t; ix++ ){}. Do you see the comma? It means, "evaluate the expression to the left, now go on and evaluate the expression to the right". The final value is the value of the last expression (ignored in this very typical case). It is different than commas in function calls because, for one thing, terms there are evaluated right to left. Also note that, at least in this case, there is another way to write this without commas: jx=0; for (ix=0; ix < t; ix++){}. AJim 01:34, 16 May 2004 (UTC)
thread_title: Describe what they do

message: This page needs an order of operations. I'll probably put it on here. 67.161.46.169 09:42, 27 December 2005 (UTC)
thread_title: order of operations

message: I just removed this sentance:
Those operators that are in C are also in Java, Perl, C#, and PHP
with the same precedence, associativity, and semantics.
From the article. I'm happy for something similar to go back in, but as it stands it is not true, as for example the comma operator, which is in C, is not in java or C#. Mrjeff 14:55, 4 June 2006 (UTC)
thread_title:  Operators in other languages 

message: I don't know the answer to this question, but it seems like a useful thing to be in this article, if someone else knows. The C-style cast operator (type) is in the table, but what about the special C++ cast operators static_cast<type>(), dynamic_cast<type>(), reinterpret_cast<type>(), and const_cast<type>()?
: These are mentioned at the top of the page. I cannot see a good reason for them not to live in the table however, so they shouldn't probably be moved there. Feel free to do so :) Mrjeff 12:13, 22 June 2006 (UTC)
replies: text:  Don't forget safe_cast<type>(), it's not official C++ but it's widely used with .Net productions and is important for .net optimization. I personally dislike .net very much but for completeness sake, it's used and recommended.Wiseguy12851 (talk) 20:36, 2 April 2010 (UTC)
replies: text: This would be appropriate to mention in articles specific to w32 programming. ―AoV² 21:16, 2 April 2010 (UTC)
thread_title:  C++ cast operators? 

message: The scope operator in C++ is different from the other operators, I think. Even if it is mentioned as an operator in some parts of the C++ standard it does not behave like an operator but as an token (or name) joiner. I.e. you cannot put parentheses around to change the order of evaluation:  if A::B::C is a valid expression, (A::B)::C has a different meaning (a C-style type cast) and A::(B::C) is a syntax error. What do you think, should we mention this special behavior of the "operator" ::? --89.55.168.117 10:46, 21 July 2006 (UTC)
thread_title:  Scope operator 

message: Recently, there was a revert to remove the Label Value Operator && from the list of C/C++ operators. While it is true that the operator is not at all standard ISO C/C++, it is a non-standard extension to some dialects, one of which is documented here. This raises the question of whether or not there should be a seperate table for operators sometimes seen as extensions to the language. I mean, such operators aren't C/C++, but they might still be of interest to some programmers. Maybe another page would be good? Extended operators?
--Cgranade 08:04, 12 October 2006 (UTC)
replies: text: Sounds good, looks good. Think I'll make the name a link, though, since it isn't clear from the table what a label value operator is exactly.
I don't get this. Why include some non-standard operator that is not found in most compilers? There is already a standard label: statement (not operator) that should be compatible with all compilers. -Andrew flame him | stalk him 23:53, 14 July 2007 (UTC)
thread_title:  Label value operator 

message: A recent edit made a large number of changes to this article, none of which I feel contribute positively to its content.  That's just my opinion, but I did revert them; here is my reasoning:
#The symbols a, b, and c as used in the table do not just represent "valid values": depending upon context, they might be object names or lvalues, as well.
#The word "declaration" has two As and one E.
#The characters &, <, and > should never be entered directly into HTML. Use the character entities instead: &, <, and >, respectively.
#The models illustrating how to overload the operators make the table seem confusing and too technical.
#Similarly, the explanation of how to overload the operators is an implementation detail; it is not, in my opinion, the job of this article to explain how to overload each operator.
I'm not going to defend the article like a hawk, but I would like to see some discussion rather than a total reversion.—Kbolino 03:49, 22 February 2007 (UTC)
replies: text: This is wiki-markup, you do not need to escape the chars.  The reason I added the overload info was that I could not find an exhaustive list anywhere (I'm writing a code generator which infers operator overloads, on mathematic objects, of course). So, I painstakingly constructed one here, looking through many sources, guidelines to arrive at these.  Yes, it makes it look technical, but this is programming, after all.  True, people might not look to wikipedia for their programming reference, however, I've noticed more lately that language documentation is exceedingly crappy.  I'd like to have a place I can lookup such overloads.  For example, look at overloading postfix increment - is that crazy or what? Anyway, it'd be sacrificing my work, and valuable screen space that will just be blank.  I'm reverting back, though taking out the spelling errorMgsloan 07:16, 22 February 2007 (UTC)
replies: text: I wrote a rather large reply, but I guess I shut off my computer before actually hitting "Save page".  I will try to recollect my thoughts and reply again.—Kbolino 23:17, 24 February 2007 (UTC)
thread_title:  Major Changes 

message: a & b == 7
means
   a & (b == 7)   ,
while
   a + b == 7
means
   (a + b) == 7   .
......Does this mean the same thing?
:No, the first does == first, the second does addition first. It's what operator precedence is all about. --King Mir (talk) 22:05, 12 January 2008 (UTC)
thread_title: & and | are arithmetic operators

message: Are there any plans on adding the stringify operator (#)?
Another operator to consider adding would be the token concatenation operator (##).
If so, how would they get added, especially considering they are only usable in macros?
Deterb (talk) 18:23, 7 December 2007 (UTC)
replies: text: The stringify and token concatenation operators are not technically C or C++ operators -- they are preprocessor operators, and are dealt with in the article C preprocessor.  I think it makes more sense to leave them there, rather than merging them here.  --Wayne Miller (talk) 18:01, 2 January 2008 (UTC)
thread_title:  C and C++ Stringify operator 

message: I would like to have it confirmed before I will edit and change this page.
so ...
statement
  e = ((a ? b : c) = d)
is not an error!
a?b:c returns reference to a or b. So we have lvalue.
Please confirm that I'm right or wrong
Varciasz (talk) 14:26, 31 January 2008 (UTC)
replies: text: You are wrong in C and right in C++. Derek farn (talk) 14:40, 31 January 2008 (UTC)

text: What Derek said. In C, the result of a conditional expression (or ternary expression) is an rvalue even if both the second and third operand are lvalues. decltype (talk) 17:12, 16 September 2009 (UTC)
replies: text: I have to insist: 'gcc (GCC) 3.4.6' compiles with the warning above!!! So if the ternary operator should expand to an rvalue, please show me where to find that in the standards. Anyway, I think this tiny detail only blurs the original message, so here is my proposal: If we change the sample code to "e = a ? b++ : b = d;", C compiler will stop with an error (postfix++ resolves to an rvalue). Plus: Now the code's goal is easier to understand: Either increment, or assign some value! I think there is nothing wrong with me rewriting the section, our discussion whether or not the current version results in an error does not conflict with the improvement. ;-) --Der schiefe Turm (talk) 15:08, 23 September 2009 (UTC)
replies: text: It's a footnote in Section 6.5.15, as seen here. It's also highlighted in Annex C of the C++ Standard as one of the differences between C++ and C. decltype (talk) 15:27, 23 September 2009 (UTC)
replies: text: THNX! --Der schiefe Turm (talk) 20:15, 23 September 2009 (UTC)
thread_title:  Error in article 

message: This page needs more links. I will start by turning some words into links (without changing the content).  —Preceding unsigned comment added by 121.44.233.63 (talk) 07:15, 14 April 2008 (UTC)
thread_title:  Adding links 

message: This is a pretty cool operator. I'm not sure if it's 'standard' or should be in the 'extensions' section, but it should be in the article. Also, I think the 'extensions' section should be expanded. The article shouldn't be 'noisy', but it should be a place where people can learn things about C++ they didn't previously know. (e.g., I had no idea about ->* or typeid()). Oh, and 'throw' is missing from the table. I'd like to know if it's overloadable.  —Preceding unsigned comment added by 207.38.195.47 (talk) 14:33, 7 May 2008 (UTC)
replies: text: The keyword typeof is a non-standard extension to the C++ language. A similar feature will be provided by the decltype keyword in C++0x. The throw keyword is a standard part of the C++ language. That said, not all keywords are operators, and I am fairly certain that neither decltype nor throw would be considered to be operators. ← Michael Safyan (talk) 02:17, 8 May 2008 (UTC)
replies: text: It's a bit confusing, but while decltype is not explicitly referred to as an operator in the WP, the term "decltype operator" is frequently used in the proposals. decltype (talk) 17:15, 16 September 2009 (UTC)

text: "throw" behaves as any other operator, except that it returns void type. The conditional operator has a special case for one operand being a throw-expression, such that "false? 3 : throw xyz()" is an expression of type int that never completes evaluation. Potatoswatter (talk) 09:43, 15 June 2010 (UTC)

text: throw can't be considered as operator, it is used in the precedence list just to mention the precedence compared with the other operators. Basic defenition of operator is, it should operate on operand. throw or return, neither way doing this as compared with other operator, both of them wouldn't be considered as operator  —Preceding unsigned comment added by Srini.ms (talk • contribs) 16:52, 28 November 2010 (UTC)
thread_title:  typeof() 

message: The section 6.5.4 "Cast operators" in the WG14 N1124 draft stands after the unary operators section 6.5.3.  According to a comment to the 6.5 "Expressions" chapter, this makes casting a lower precedence operator than unary operators.  But I understand that there is no way to write a test for this as both cast and unary kinds apply to one operand and thus cannot be interpreted differently. --ilgiz (talk) 01:20, 29 January 2009 (UTC)
thread_title:  Precedence of type casting in plain C 

message: I see that once again "this" has been removed. Even if technically not an operator, I think it should be here somehow, because I think many will try to find it here. At least could we have a discussion about it instead of an edit war. SimonTrew (talk) 17:34, 27 February 2009 (UTC)
replies: text: Yes, I considered adding a comment on the talk page. But I felt that my edit comment would be enough to settle the issue: removed "this" from the table, per [class.this]/1 of the standard. this is not an operator, so I think it's just confusing to have it in a list of operators. Possibly a mention at the bottom of the article, but not in the actual table. Just my 5c. decltype 19:06, 27 February 2009 (UTC)
replies: text: Yeah I was kinda thinking the same myself. But actually I am coming round to your opinion and wonder if it is justified at all in this article, it's not difficult to search for. I'm just quite a fan of making cross-references, I think that is part of what gives Wikipedia its value. SimonTrew (talk) 06:57, 28 February 2009 (UTC)

text: See §5.1. "this" is a primary-expression. As such, it behaves like a literal. Operators typically operate on things. What's the difference between a nullary operator and an identifier? You could argue that every keyword is an operator. "static" operates on declarations, for example. Potatoswatter (talk) 09:39, 15 June 2010 (UTC)
thread_title:  "this" 

message: The article sais that the postfix ++ operator is performed last; This should be: it is performed before returning a value, but the returned value is the old (unincremented) one. Can anyone change this? —Preceding unsigned comment added by 132.229.16.187 (talk • contribs) 12:35, 8 May 2009 (UTC)
replies: text: The actual time when the increment happens is unspecified (as long as it is between the appropriate sequence points). Eric119 (talk) 16:04, 8 May 2009 (UTC)
thread_title: Pre- and postfix ++/--

message: It's much more efficient simply to say, "all arithmetic operators [e.g.] are overloadable." The advantage of consistency of content from table to table is not enough to make up for the costs in terms of: table code complexity; information redundancy; filesize. ᛭ LokiClock (talk) 21:17, 20 April 2010 (UTC)
replies: text: This reflects the fact that the operators previously were all in one continuous table. I only split them apart on account of the , as while making other additions I realized a section which starts mid-table cannot provide a meaningful edit preview. I might re-write all of this from scratch in a week or two but I’m busy at the moment. For one, I’d like to reduce the width of the “yes”/“no” cells, combine the member vs. global operator prototypes into one cell, among other things. I’d also like to discuss common overloading paradigms but perhaps a separate article would be appropriate for that. ―AoV² 22:35, 20 April 2010 (UTC)
replies: text: ..So, it's okay to remove the column, right? And for "included in C"? ᛭ LokiClock (talk) 03:59, 15 May 2010 (UTC)
replies: text:  Even after 10 years, I'd favour to remove redundant "all yes" columns and replace them by a small text between sub-heading and table, as suggested by User:LokiClock. --RokerHRO (talk) 20:56, 5 February 2021 (UTC)
thread_title:  Get rid of Overloadable column for those all-yes 

message: There's no indication of what the type "R" means. OrangeDog (τ • ε) 10:33, 23 June 2010 (UTC)
thread_title:  Overload prototypes 

message: Compound literals are classified as "postfix operators" in C (ISO/IEC 9899:1990 §6.3.2.5, ISO 9899:1999 §6.5.2.5). They are not included in C++, and they are missing from this article as far as I can see. For those who haven't encountered them, an example of a compound literal, straight from the C90 standard: p = (int []){2, 4};, or read DrDobbs for more details. Note that it has nothing to do with type casting. How about a passing mention? --Cubbi (talk) 03:35, 20 September 2010 (UTC)
thread_title:  Compound literals missing 

message: From Operators_in_C_and_C%2B%2B#Notes:
"* For example, ++x*3 is ambiguous without some precedence rule(s). The precedence table tells us that: x is 'bound' more tightly to ++ than to *, so that whatever ++ does (now or later—see below), it does it ONLY to x (and not to x*3); it is equivalent to (++x, x*3)."
This looks like it is saying that ++x*3 is equivalent to (++x, x*3). Which is incorrect: with the comma operator, the arguments can be evaluated in any order.
EDIT: I wasn't aware of sequence points.
Nevermind! :)
Muntoo (talk) 23:21, 1 November 2011 (UTC)
thread_title:  Notes 

message: C11 defines an alignment operator _Alignof. I have read about something similar in C++11, although I can't find anyone that actually references the ISO/IEC 14882:2011 document. If anyone know the standards better than I, then please add information about it. Caesar (talk) 08:05, 7 February 2012 (UTC)
replies: text: Answering myself, the aligment operator of C++ is alignof, according to chapter 3.11, "Alignment", of ISO/IEC 14882:2011. That is also the name of the macro included in the C header stdalign.h. Caesar (talk) 22:19, 7 February 2012 (UTC)
thread_title:  Alignment operators 

message: Unless I'm wrong, there's something amiss with the return types of most overloaded binary operators as shown on the page. They return values, not references, but use reference arguments (right hand operands). This means that in their current state as shown on the page, they cannot be used in right-to-left algebraic expressions (e.g.: a + (b + c) will trigger a compiler error, unless (b + c) is stored in a variable first and used as such).--Printz150 (talk) 18:58, 25 February 2012 (UTC)
replies: text: No. Since binary operator always returns a result without changing one of the operands, this result is saved and returned via temp variable. Since you cannot return reference to temp variable :you should do it by value  — Preceding unsigned comment added by 2.94.232.187 (talk) 16:08, 9 November 2012 (UTC)
thread_title:  Non-reference return types 

message: What about this one ? (New in C++11)
Declaration is like : 
int operator"" _stuff ( int val);
And use would be : int x = 36_stuff;
Doom Oo7 (talk) 09:27, 23 August 2013 (UTC)
thread_title:  User-defined literals 

message: As noted above, this page is a heavily used reference.
Some time ago someone removed all const-correctness from the prototype references. Why was that? Can we get it back? Because unless something fundamental changed about C++ recently it is technically deficient now. (And trying to fix const errors when people are overloading operators for the first time is frustrating enough already on C++ forums without them coming to Wikipedia and finding contradictory information.)
Duoas (talk) 22:06, 6 May 2014 (UTC)
thread_title:  const-correctness 

message: The precedence table says that the ternary-operator has higher precedence than the assign-operator, so "a ? b : c = 1" should be evaluated like "(a ? b : c) = 1". In reality it is evaluated like "a ? b : (c = 1)". So the precedence table looks wrong.
See: 
http://stackoverflow.com/questions/7499400/ternary-conditional-and-assignment-operator-precedence
and 
http://en.cppreference.com/w/cpp/language/operator_precedence  — Preceding unsigned comment added by 2.244.33.171 (talk) 20:36, 15 June 2015 (UTC)
replies: text: Done. ZBalling (talk) 09:21, 22 September 2019 (UTC)
thread_title:  Wrong operator precedence with ternary- and assign-operator 

message: I searched through this article but found that there was no column for the usage and the logical purpose of these operators. Maybe I will include them in a new column.Debanshu.Das (talk) 04:55, 4 August 2020 (UTC)
replies: text: No, there is no place for that. 109.252.94.59 (talk) 02:38, 16 January 2021 (UTC)
thread_title:  Include uses of operators 

message: Albeit it might look like an operator, and many other sources list it as operator, it is not an operator, because it does not combine two arbitrary expressions to create a new one. Instead it combines two names or identifiers to form a new (function, type or variable) name. So it works completely on another level at compile-time only.
And, of course, as a name-building token it has no "associativity", because a name A::B::C cannot be written neither as (A::B)::C – that would be a C-style typecast – nor as A::(B::C) – that would be a syntax error. --RokerHRO (talk) 21:04, 5 February 2021 (UTC)
thread_title:  I'd remove the scope resolution "operator" 

message: Given that
    a++;
changes the objects internal value and is equivalent to
    a+=1;
for numerical objects, shouldn't the increment/decrement operators be considered assignment operators? 80.62.116.42 (talk) 07:45, 17 October 2022 (UTC)
thread_title:  Should the increment/decrement operators be considered assignment operators? 

message: Why mention  ??!=  along with |=  or ??( along with < ?  These ??-trigraphs are meant to represent characters such as | and < when they are not available in the code page of the hardware. This replacement is ALWAYS done by the preprocessor, not just in operators. -- Wassermaus (talk) 22:32, 26 October 2023 (UTC)
replies: text: At first, this article only mentioned the alternative keyword representations (like or). So, for consistency, I added digraphs since they were added to the standards at the same time and for the same reason. However, adding digraphs but not trigraphs also seemed inconsistent since they can both be used to represent the operators. a??(0??) and a<:0:> mean exactly the same thing despite the former being just a[0] after the preprocessor and the latter using alternartive tokens with the same meaning. To a programmer using them it's a distinction without a difference. In addition, a or b is implemented as a keyword in C++ and as a macro in C. So, I argue that there is precedent to adding preprocessor substitutions to the list. And lastly, as you correctly said, trigraphs can also appear outside operators. However, that's also true for the keywords since in e.g. the declaration int and a = 0; the and is not an operator. Nickps (talk) 09:25, 27 October 2023 (UTC)
replies: text: After noticing that I still missed some digraphs and trigraphs on the conversion operators i.e.R<%a%> and R??<a??> plus the ones with auto, I realised the whole thing is pointless and removed all alternative spellings. If anyone disagrees they are free to revert but I don't think it's worth it. My argument above still stands which is why I also removed the operator synonyms like and. Nickps (talk) 22:54, 8 May 2024 (UTC)
thread_title:  Remove trigraphs 

message: The C23 standard adds the operators typeof and typeof_unqual and refers to them as operators by name (ISO/IEC 9899/2023 6.7.2.5 Typeof specifiers says: "The typeof and typeof_unqual tokens are collectively called the typeof operators.") While neither operator is in C++ yet, they will almost certainly be added to C++26 for compatibility and the proposal that does so, p2958, groups them together with decltype, which makes sense. However, I can't find any source that refers to decltype as an "operator". In the decltype page one of the references is called decltype operator, but that name has since been changed to "decltype Type Specifier". (EDIT: Some examples of the phrase "decltype operator" I found:   and the original paper that proposed it. I think the fact that the people who defined decltype in the first place called it an operator is enough to settle the question, but I'll leave this here in case someone disagrees. --19:42, 30 October 2023 (UTC)
thread_title:  Is <code>decltype</code> an operator?