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{{title|C++ Operator Precedence}}
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#REDIRECT [[enwiki:Rust_(programming_language)]]
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{{cpp/language/expressions/navbar}}
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The following table lists the precedence and associativity of C++ operators. Operators are listed top to bottom, in descending precedence.
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{|class="wikitable"
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|-
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!style="text-align: left"|Precedence
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!style="text-align: left"|Operator
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!style="text-align: left"|Description
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!style="text-align: left"|Associativity
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|-
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!1<!-- Numbering should start from the highest precedence. See also the discussion page. -->
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|{{tt|::}}
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|{{rlp|identifiers#Qualified_identifiers|Scope resolution}}
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|style="vertical-align: top" rowspan="6"|Left-to-right &#8594;
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|-
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!rowspan=5|2
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|style="border-bottom-style: none"|{{tt|a++}} &nbsp; {{tt|a--}}
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|style="border-bottom-style: none"|Suffix/postfix {{rlp|operator incdec|increment and decrement}}
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|-
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|style="border-bottom-style: none; border-top-style: none"|{{tt|''type''()}} &nbsp; {{tt|''type''{} }}
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|style="border-bottom-style: none; border-top-style: none"|{{rlp|explicit cast|Functional cast}}
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|-
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|style="border-bottom-style: none; border-top-style: none"|{{tt|a()}}
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|style="border-bottom-style: none; border-top-style: none"|{{rlp|operator_other#Built-in_function_call_operator|Function call}}
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|-
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|style="border-bottom-style: none; border-top-style: none"|{{tt|a[]}}
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|style="border-bottom-style: none; border-top-style: none"|{{rlp|operator_member_access#Built-in_subscript_operator|Subscript}}
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|-
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|style="border-bottom-style: none; border-top-style: none"|{{tt|.}} &nbsp; {{tt|->}}
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|style="border-bottom-style: none; border-top-style: none"|{{rlp|operator_member_access#Built-in_member_access_operators|Member access}}
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|-
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!rowspan=10|3
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|style="border-bottom-style: none"|{{tt|++a}} &nbsp; {{tt|--a}}
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|style="border-bottom-style: none"|Prefix {{rlp|operator incdec|increment and decrement}}
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|style="vertical-align: top" rowspan="10"|Right-to-left &#8592;
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|-
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|style="border-bottom-style: none; border-top-style: none"|{{tt|+a}} &nbsp; {{tt|-a}}
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|style="border-bottom-style: none; border-top-style: none"|Unary {{rlp|operator_arithmetic#Unary_arithmetic_operators|plus and minus}}
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|-
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|style="border-bottom-style: none; border-top-style: none"|{{tt|!}} &nbsp; {{tt|~}}
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|style="border-bottom-style: none; border-top-style: none"|{{rlp|operator logical|Logical NOT}} and {{rlp|operator_arithmetic#Bitwise_logic_operators|bitwise NOT}}
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|-
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|style="border-bottom-style: none; border-top-style: none"|{{tt|(''type'')}}
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|style="border-bottom-style: none; border-top-style: none"|{{rlp|explicit cast|C-style cast}}
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|-
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|style="border-bottom-style: none; border-top-style: none"|{{tt|*a}}
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|style="border-bottom-style: none; border-top-style: none"|{{rlp|operator_member_access#Built-in_indirection_operator|Indirection}} (dereference)
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|-
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|style="border-bottom-style: none; border-top-style: none"|{{tt|&a}}
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|style="border-bottom-style: none; border-top-style: none"|{{rlp|operator_member_access#Built-in_address-of_operator|Address-of}}
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|-
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|style="border-bottom-style: none; border-top-style: none"|{{rlpt|sizeof}}
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|style="border-bottom-style: none; border-top-style: none"|{{rlp|sizeof|Size-of}}<ref group="note">The operand of {{tt|sizeof}} can't be a C-style type cast: the expression {{c|sizeof (int) * p}} is unambiguously interpreted as {{c|(sizeof(int)) * p}}, but not {{c|sizeof((int)*p)}}.</ref>
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|-
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|style="border-bottom-style: none; border-top-style: none"|{{ltt|cpp/keyword/co_await}}
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|style="border-bottom-style: none; border-top-style: none"|{{rlp|coroutines|await-expression}} {{mark c++20}}
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|-
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|style="border-bottom-style: none; border-top-style: none"|{{rlpt|new}} &nbsp; {{rlpt|new|new[]}}
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|style="border-bottom-style: none; border-top-style: none"|{{rlp|new|Dynamic memory allocation}}
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|-
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|style="border-top-style: none"|{{rlpt|delete}} &nbsp; {{rlpt|delete|delete[]}}
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|style="border-top-style: none"|{{rlp|delete|Dynamic memory deallocation}}
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|-
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!4
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|{{tt|.*}} &nbsp; {{tt|->*}}
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|{{rlp|operator_member_access#Built-in_pointer-to-member_access_operators|Pointer-to-member}}
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|style="vertical-align: top" rowspan="12"|Left-to-right &#8594;
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|-
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!5
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|{{tt|a*b}} &nbsp; {{tt|a/b}} &nbsp; {{tt|a%b}}
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|{{rlp|operator_arithmetic#Multiplicative_operators|Multiplication, division, and remainder}}
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|-
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!6
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|{{tt|a+b}} &nbsp; {{tt|a-b}}
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|{{rlp|operator_arithmetic#Additive_operators|Addition and subtraction}}
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|-
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!7
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|{{tt|<<}} &nbsp; {{tt|>>}}
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|Bitwise {{rlp|operator_arithmetic#Bitwise_shift_operators|left shift and right shift}}
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|-
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!8
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|{{tt|1= <=>}}
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|[[cpp/language/operator_comparison#Three-way_comparison|Three-way comparison operator]] {{mark since c++20}}
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|-
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!9
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|{{tt|<}} &nbsp; {{tt|1= <=}} &nbsp; {{tt|>}} &nbsp; {{tt|1= >=}}
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|For {{rlp|operator_comparison|relational operators}} < and ≤ and > and ≥ respectively
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|-
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!10
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|{{tt|1= ==}} &nbsp; {{tt|1= !=}}
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|For {{rlp|operator_comparison|equality operators}} = and ≠ respectively
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|-
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!11
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|{{tt|a&b}}
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|{{rlp|operator_arithmetic#Bitwise_logic_operators|Bitwise AND}}
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|-
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!12
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|{{tt|^}}
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|{{rlp|operator_arithmetic#Bitwise_logic_operators|Bitwise XOR}} (exclusive or)
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|-
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!13
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|<code><nowiki>|</nowiki></code>
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|{{rlp|operator_arithmetic#Bitwise_logic_operators|Bitwise OR}} (inclusive or)
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|-
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!14
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|{{tt|&&}}
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|{{rlp|operator_logical|Logical AND}}
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|-
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!15
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|<code><nowiki>||</nowiki></code>
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|{{rlp|operator_logical|Logical OR}}
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|-
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!rowspan=8|16
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|style="border-bottom-style: none"|{{tt|a?b:c}}
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|style="border-bottom-style: none"|{{rlp|operator_other#Conditional_operator|Ternary conditional}}<ref group="note">The expression in the middle of the conditional operator (between {{ttb|?}} and {{ttb|:}}) is parsed as if parenthesized: its precedence relative to {{ttb|?:}} is ignored.</ref>
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|style="vertical-align: top" rowspan="8"|Right-to-left &#8592;
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|-
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|style="border-bottom-style: none; border-top-style: none"|{{rlpt|throw}}
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|style="border-bottom-style: none; border-top-style: none"|{{rlp|throw|throw operator}}
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|-
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|style="border-bottom-style: none; border-top-style: none"|{{ltt|cpp/keyword/co_yield}}
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|style="border-bottom-style: none; border-top-style: none"|{{rlp|coroutines|yield-expression}} {{mark c++20}}
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|-
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|style="border-bottom-style: none; border-top-style: none"|{{tt|1= =}}
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|style="border-bottom-style: none; border-top-style: none"|{{rlp|operator_assignment#Builtin_direct_assignment|Direct assignment}} (provided by default for C++ classes)
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|-
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|style="border-bottom-style: none; border-top-style: none"|{{tt|1= +=}} &nbsp; {{tt|1= -=}}
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|style="border-bottom-style: none; border-top-style: none"|{{rlp|operator_assignment#Builtin_compound_assignment|Compound assignment}} by sum and difference
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|-
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|style="border-bottom-style: none; border-top-style: none"|{{tt|1= *=}} &nbsp; {{tt|1= /=}} &nbsp; {{tt|1= %=}}
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|style="border-bottom-style: none; border-top-style: none"|{{rlp|operator_assignment#Builtin_compound_assignment|Compound assignment}} by product, quotient, and remainder
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|-
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|style="border-bottom-style: none; border-top-style: none"|{{tt|1= <<=}} &nbsp; {{tt|1= >>=}}
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|style="border-bottom-style: none; border-top-style: none"|{{rlp|operator_assignment#Builtin_compound_assignment|Compound assignment}} by bitwise left shift and right shift
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|-
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|style="border-top-style: none"|{{tt|1= &=}} &nbsp; {{tt|1= ^=}} &nbsp; {{tt|1= {{!}}=}}
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|style="border-top-style: none"|{{rlp|operator_assignment#Builtin_compound_assignment|Compound assignment}} by bitwise AND, XOR, and OR
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|-
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!17
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|{{tt|,}}
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|{{rlp|operator_other#Built-in_comma_operator|Comma}}
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|Left-to-right &#8594;
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|}
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<references group="note" />
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When parsing an expression, an operator which is listed on some row of the table above with a precedence will be bound tighter (as if by parentheses) to its arguments than any operator that is listed on a row further below it with a lower precedence. For example, the expressions {{c|std::cout << a & b}} and  {{c|*p++}} are parsed as {{c|(std::cout << a) & b}} and {{c|*(p++)}}, and not as {{c|std::cout << (a & b)}} or {{c|(*p)++}}.
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Operators that have the same precedence are bound to their arguments in the direction of their associativity. For example, the expression {{c|1=a = b = c}} is parsed as {{c|1=a = (b = c)}}, and not as {{c|1=(a = b) = c}} because of right-to-left associativity of assignment, but {{c|a + b - c}} is parsed {{c|(a + b) - c}} and not {{c|a + (b - c)}} because of left-to-right associativity of addition and subtraction.
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Associativity specification is redundant for unary operators and is only shown for completeness: unary prefix operators always associate right-to-left ({{c|delete ++*p}} is {{c|delete(++(*p))}}) and unary postfix operators always associate left-to-right ({{c|a[1][2]++}} is {{c|((a[1])[2])++}}). Note that the associativity is meaningful for member access operators, even though they are grouped with unary postfix operators: {{c|a.b++}} is parsed {{c|(a.b)++}} and not {{c|a.(b++)}}.
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Operator precedence is unaffected by {{rlp|operators|operator overloading}}. For example, {{c|std::cout << a ? b : c;}} parses as {{c|(std::cout << a) ? b : c;}} because the precedence of arithmetic left shift is higher than the conditional operator.
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===Notes===
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Precedence and associativity are compile-time concepts and are independent from {{rlp|eval_order|order of evaluation}}, which is a runtime concept.
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The standard itself doesn't specify precedence levels. They are derived from the grammar.
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{{rlpt|const_cast}}, {{rlpt|static_cast}}, {{rlpt|dynamic_cast}}, {{rlpt|reinterpret_cast}}, {{rlpt|typeid}}, {{rlpt|sizeof...}}, {{rlpt|noexcept}} and {{rlpt|alignof}} are not included since they are never ambiguous.
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Some of the operators have {{rlp|operator_alternative|alternate spellings}} (e.g., {{c|and}} for {{tt|&&}}, {{c|or}} for {{tt|{{!!}}}}, {{c|not}} for {{tt|!}}, etc.).
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In C, the ternary conditional operator has higher precedence than assignment operators. Therefore, the expression {{c|1=e = a < d ? a++ : a = d}}, which is parsed in C++ as {{c|1=e = ((a < d) ? (a++) : (a = d))}}, will fail to compile in C due to grammatical or semantic constraints in C. See the corresponding C page for details.
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===See also===
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{{cpp/language/operators}}
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{{dsc begin}}
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{{dsc see c|c/language/operator_precedence|C operator precedence|nomono=true}}
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{{dsc end}}
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{{langlinks|ar|cs|de|es|fr|it|ja|ko|pt|ru|tr|zh}}
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Revision as of 09:15, 31 July 2023

#REDIRECTenwiki:Rust (programming language)
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