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Difference between revisions of "cpp/string/basic string/swap2"

From cppreference.com
< cpp‎ | string‎ | basic string
(merge noexcept)
m (→‎Synopsis: ~constexpr since)
 
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{{cpp/title | swap<small>(std::basic_string)</small>}}
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{{cpp/title|swap{{small|(std::basic_string)}}}}
 
{{cpp/string/basic_string/navbar}}
 
{{cpp/string/basic_string/navbar}}
 
{{dcl begin}}
 
{{dcl begin}}
−
{{dcl | until=c++17 |
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{{dcl header|string}}
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{{dcl rev multi
 +
|until1=c++17|dcl1=
 
template< class CharT, class Traits, class Alloc >
 
template< class CharT, class Traits, class Alloc >
−
void swap( std::basic_string<CharT, Traits, Alloc> &lhs,
+
void swap( std::basic_string<CharT, Traits, Alloc>& lhs,
−
           std::basic_string<CharT, Traits, Alloc> &rhs );
+
           std::basic_string<CharT, Traits, Alloc>& rhs );
−
}}
+
|notes2={{mark constexpr since c++20}}|dcl2=
−
{{dcl | since=c++17 |
+
 
template< class CharT, class Traits, class Alloc >
 
template< class CharT, class Traits, class Alloc >
−
void swap( std::basic_string<CharT, Traits, Alloc> &lhs,
+
void swap( std::basic_string<CharT, Traits, Alloc>& lhs,
−
           std::basic_string<CharT, Traits, Alloc> &rhs ) noexcept(/* see below */);
+
           std::basic_string<CharT, Traits, Alloc>& rhs ) noexcept(/* see below */);
 
}}
 
}}
 
{{dcl end}}
 
{{dcl end}}
  
−
Specializes the {{lc|std::swap}} algorithm for {{lc|std::basic_string}}. Swaps the contents of {{tt|lhs}} and {{tt|rhs}}. Equivalent to {{c|lhs.swap(rhs)}}.
+
Specializes the {{lc|std::swap}} algorithm for {{lc|std::basic_string}}. Swaps the contents of {{c|lhs}} and {{c|rhs}}.
 +
 
 +
Equivalent to {{c|lhs.swap(rhs)}}.
  
 
===Parameters===
 
===Parameters===
 
{{par begin}}
 
{{par begin}}
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{{par | lhs, rhs | strings whose contents to swap}}
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{{par|lhs, rhs|strings whose contents to swap}}
−
{{par end}}  
+
{{par end}}
  
 
===Return value===
 
===Return value===
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Constant.
 
Constant.
  
−
{{rev begin}}
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{{rrev|since=c++17|
−
{{rev |since=c++17|
+
 
===Exceptions===
 
===Exceptions===
 
{{noexcept|noexcept(lhs.swap(rhs))}}
 
{{noexcept|noexcept(lhs.swap(rhs))}}
 
}}
 
}}
−
{{rev end}}
+
 
 +
===Example===
 +
{{example
 +
|code=
 +
#include <iostream>
 +
#include <string>
 +
 
 +
int main()
 +
{
 +
    std::string a = "AAA";
 +
    std::string b = "BBBB";
 +
 +
    std::cout << "Before swap:\n"
 +
                "a = " << a << "\n"
 +
                "b = " << b << "\n\n";
 +
 
 +
    std::swap(a, b);
 +
 
 +
    std::cout << "After swap:\n"
 +
                "a = " << a << "\n"
 +
                "b = " << b << '\n';
 +
}
 +
 
 +
|output=
 +
Before swap:
 +
a = AAA
 +
b = BBBB
 +
 +
After swap:
 +
a = BBBB
 +
b = AAA
 +
}}
 +
 
 +
===Defect reports===
 +
{{dr list begin}}
 +
{{dr list item|wg=lwg|dr=2064|std=C++11|before=non-member {{tt|swap}} was noexcept and inconsistent with member {{tt|swap}}|after=noexcept removed}}
 +
{{dr list end}}
  
 
===See also===
 
===See also===
 
{{dsc begin}}
 
{{dsc begin}}
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{{dsc inc | cpp/string/basic_string/dsc swap}}
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{{dsc inc|cpp/string/basic_string/dsc swap}}
 
{{dsc end}}
 
{{dsc end}}
  
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[[de:cpp/string/basic string/swap2]]
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{{langlinks|de|es|fr|it|ja|pt|ru|zh}}
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[[es:cpp/string/basic string/swap2]]
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−
[[fr:cpp/string/basic string/swap2]]
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−
[[it:cpp/string/basic string/swap2]]
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−
[[ja:cpp/string/basic string/swap2]]
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−
[[pt:cpp/string/basic string/swap2]]
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−
[[ru:cpp/string/basic string/swap2]]
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−
[[zh:cpp/string/basic string/swap2]]
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Latest revision as of 10:47, 18 April 2024

 
C++
 
Strings library
 
std::basic_string
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swap(std::basic_string)
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(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)
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Defined in header <string>
template< class CharT, class Traits, class Alloc >

void swap( std::basic_string<CharT, Traits, Alloc>& lhs,

           std::basic_string<CharT, Traits, Alloc>& rhs );
 (until C++17)
template< class CharT, class Traits, class Alloc >

void swap( std::basic_string<CharT, Traits, Alloc>& lhs,

           std::basic_string<CharT, Traits, Alloc>& rhs ) noexcept(/* see below */);
 (since C++17)
(constexpr since C++20)

Specializes the std::swap algorithm for std::basic_string. Swaps the contents of lhs and rhs.

Equivalent to lhs.swap(rhs).

Contents

[edit] Parameters

lhs, rhs - strings whose contents to swap

[edit] Return value

(none)

[edit] Complexity

Constant.

Exceptions

noexcept specification:  
noexcept(noexcept(lhs.swap(rhs)))
 (since C++17)

[edit] Example

Run this code
#include <iostream>
#include <string>
 
int main()
{
    std::string a = "AAA";
    std::string b = "BBBB";
 
    std::cout << "Before swap:\n"
                 "a = " << a << "\n"
                 "b = " << b << "\n\n";
 
    std::swap(a, b);
 
    std::cout << "After swap:\n"
                 "a = " << a << "\n"
                 "b = " << b << '\n';
}

Output: 

Before swap:
a = AAA
b = BBBB
 
After swap:
a = BBBB
b = AAA

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 2064 C++11 non-member swap was noexcept and inconsistent with member swap noexcept removed

[edit] See also

 swaps the contents
(public member function) [edit]
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