168 lines
6.9 KiB
Markdown
168 lines
6.9 KiB
Markdown
[over.oper.general]
|
||
|
||
# 12 Overloading [[over]](./#over)
|
||
|
||
## 12.4 Overloaded operators [[over.oper]](over.oper#general)
|
||
|
||
### 12.4.1 General [over.oper.general]
|
||
|
||
[1](#1)
|
||
|
||
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L3338)
|
||
|
||
A declaration
|
||
whose [*declarator-id*](dcl.decl.general#nt:declarator-id "9.3.1 General [dcl.decl.general]") is an [*operator-function-id*](#nt:operator-function-id "12.4.1 General [over.oper.general]") shall declare a function or function template or
|
||
an explicit instantiation or specialization of a function template[.](#1.sentence-1)
|
||
|
||
A function so declared is an [*operator function*](#def:function,operator "12.4.1 General [over.oper.general]")[.](#1.sentence-2)
|
||
|
||
A function template so declared is
|
||
an [*operator function template*](#def:function,operator,template "12.4.1 General [over.oper.general]")[.](#1.sentence-3)
|
||
|
||
A specialization of an operator function template is also an operator function[.](#1.sentence-4)
|
||
|
||
An operator function is said to[*implement*](#def:operator,implementation "12.4.1 General [over.oper.general]") the operator named in its[*operator-function-id*](#nt:operator-function-id "12.4.1 General [over.oper.general]")[.](#1.sentence-5)
|
||
|
||
[operator-function-id:](#nt:operator-function-id "12.4.1 General [over.oper.general]")
|
||
operator [*operator*](#nt:operator "12.4.1 General [over.oper.general]")
|
||
|
||
[operator:](#nt:operator "12.4.1 General [over.oper.general]") one of
|
||
new delete new[] delete[] co_await ( ) [ ] -> ->*
|
||
~ ! + - * / % ^ &
|
||
| = += -= *= /= %= ^= &=
|
||
|= == != < > <= >= <=> &&
|
||
|| << >> <<= >>= ++ -- ,
|
||
|
||
[*Note [1](#note-1)*:
|
||
|
||
The operatorsnew[],delete[],(),
|
||
and[] are formed from more than one token[.](#1.sentence-6)
|
||
|
||
The latter two operators are [function call](expr.call "7.6.1.3 Function call [expr.call]") and [subscripting](expr.sub "7.6.1.2 Subscripting [expr.sub]")[.](#1.sentence-7)
|
||
|
||
â *end note*]
|
||
|
||
[2](#2)
|
||
|
||
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L3382)
|
||
|
||
Both the unary and binary forms of
|
||
|
||
+ - * &
|
||
|
||
can be overloaded[.](#2.sentence-1)
|
||
|
||
[3](#3)
|
||
|
||
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L3389)
|
||
|
||
[*Note [2](#note-2)*:
|
||
|
||
The following operators cannot be overloaded:
|
||
|
||
. .* :: ?:
|
||
|
||
nor can the preprocessing symbols# ([[cpp.stringize]](cpp.stringize "15.7.3 The # operator"))
|
||
and## ([[cpp.concat]](cpp.concat "15.7.4 The ## operator"))[.](#3.sentence-1)
|
||
|
||
â *end note*]
|
||
|
||
[4](#4)
|
||
|
||
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L3402)
|
||
|
||
Operator functions are usually not called directly; instead they are invoked
|
||
to evaluate the operators they implement ([[over.unary]](over.unary "12.4.2 Unary operators") â [[over.inc]](over.inc "12.4.7 Increment and decrement"))[.](#4.sentence-1)
|
||
|
||
They can be explicitly called, however, using the[*operator-function-id*](#nt:operator-function-id "12.4.1 General [over.oper.general]") as the name of the function in the function call syntax ([[expr.call]](expr.call "7.6.1.3 Function call"))[.](#4.sentence-2)
|
||
|
||
[*Example [1](#example-1)*: complex z = a.operator+(b); // complex z = a+b;void* p = operator new(sizeof(int)*n); â *end example*]
|
||
|
||
[5](#5)
|
||
|
||
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L3416)
|
||
|
||
The allocation and deallocation functions,operator new,operator new[],operator delete, andoperator delete[],
|
||
are described completely in [[basic.stc.dynamic]](basic.stc.dynamic "6.8.6.5 Dynamic storage duration")[.](#5.sentence-1)
|
||
|
||
The attributes and restrictions
|
||
found in the rest of [[over.oper]](over.oper "12.4 Overloaded operators") do not apply to them unless explicitly
|
||
stated in [[basic.stc.dynamic]](basic.stc.dynamic "6.8.6.5 Dynamic storage duration")[.](#5.sentence-2)
|
||
|
||
[6](#6)
|
||
|
||
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L3427)
|
||
|
||
The co_await operator is described completely in [[expr.await]](expr.await "7.6.2.4 Await")[.](#6.sentence-1)
|
||
|
||
The attributes and restrictions
|
||
found in the rest of [[over.oper]](over.oper "12.4 Overloaded operators") do not apply to it unless explicitly
|
||
stated in [[expr.await]](expr.await "7.6.2.4 Await")[.](#6.sentence-2)
|
||
|
||
[7](#7)
|
||
|
||
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L3433)
|
||
|
||
An operator function
|
||
shall have at least one
|
||
function parameter or implicit object parameter whose type is
|
||
a class, a reference to a class, an
|
||
enumeration, or a reference to an enumeration[.](#7.sentence-1)
|
||
|
||
It is not possible to change the precedence, grouping, or number of operands
|
||
of operators[.](#7.sentence-2)
|
||
|
||
The meaning of
|
||
the operators =, (unary) &, and , (comma),
|
||
predefined for each type, can be changed for specific class types by
|
||
defining operator functions that implement these operators[.](#7.sentence-3)
|
||
|
||
Likewise, the meaning of the operators (unary) & and , (comma)
|
||
can be changed for specific enumeration types[.](#7.sentence-4)
|
||
|
||
Operator functions are inherited in the same manner as other base class
|
||
functions[.](#7.sentence-5)
|
||
|
||
[8](#8)
|
||
|
||
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L3452)
|
||
|
||
An operator function shall be a
|
||
prefix unary, binary, function call, subscripting, class member access, increment, or decrement
|
||
operator function[.](#8.sentence-1)
|
||
|
||
[9](#9)
|
||
|
||
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L3457)
|
||
|
||
[*Note [3](#note-3)*:
|
||
|
||
The identities among certain predefined operators applied to fundamental types
|
||
(for example,++a ≡a+=1)
|
||
need not hold for operator functions[.](#9.sentence-1)
|
||
|
||
Some predefined operators, such as+=,
|
||
require an operand to be an lvalue when applied to fundamental types;
|
||
this is not required by operator functions[.](#9.sentence-2)
|
||
|
||
â *end note*]
|
||
|
||
[10](#10)
|
||
|
||
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L3471)
|
||
|
||
An operator function cannot have [default arguments](dcl.fct.default "9.3.4.7 Default arguments [dcl.fct.default]"),
|
||
except where explicitly stated below[.](#10.sentence-1)
|
||
|
||
Operator
|
||
functions cannot have more or fewer parameters than the
|
||
number required for the corresponding operator, as
|
||
described in the rest of [[over.oper]](over.oper "12.4 Overloaded operators")[.](#10.sentence-2)
|
||
|
||
[11](#11)
|
||
|
||
[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/overloading.tex#L3480)
|
||
|
||
Operators not mentioned explicitly in subclauses [[over.assign]](over.assign "12.4.3.2 Simple assignment") through [[over.inc]](over.inc "12.4.7 Increment and decrement") act as ordinary unary and binary
|
||
operators obeying the rules of [[over.unary]](over.unary "12.4.2 Unary operators") or [[over.binary]](over.binary "12.4.3 Binary operators")[.](#11.sentence-1)
|