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cppdraft/over/oper/general.md

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+[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)
+
+— *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)
+
+— *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") – [[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); — *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)
+
+— *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)