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Difference between revisions of "Template:cpp/container/back"

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{{cpp/container/{{{1|}}}/title | back}}
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{{#vardefine:cont|{{{1|vector}}}}}<!--
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{{cpp/container/{{{1|}}}/sidebar}}
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-->{{cpp/container/{{#var:cont}}/title|back}}
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{{ddcl list begin}}
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{{cpp/container/{{#var:cont}}/navbar}}
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{{ddcl list item | notes={{cpp/container/mark c++0x feature | {{{1|}}} }} |
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{{dcl begin}}
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{{#switch:{{#var:cont}}
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|array=
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{{dcl|num=1|since=c++11|notes={{mark constexpr since c++17}}|
 
reference back();
 
reference back();
 
}}
 
}}
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{{ddcl list item | notes={{cpp/container/mark c++0x feature | {{{1|}}} }} |
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{{dcl|num=2|since=c++11|notes={{mark constexpr since c++14}}|
 
const_reference back() const;
 
const_reference back() const;
 
}}
 
}}
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{{ddcl list end}}
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|vector=
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{{dcl|num=1|notes={{mark constexpr since c++20}}|
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reference back();
 +
}}
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{{dcl|num=2|notes={{mark constexpr since c++20}}|
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const_reference back() const;
 +
}}
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|inplace_vector=
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{{dcl|num=1|since=c++26|
 +
constexpr reference back();
 +
}}
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{{dcl|num=2|since=c++26|
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constexpr const_reference back() const;
 +
}}
 +
|
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{{dcl|num=1|since={{cpp/std|{{#var:cont}}}}|
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reference back();
 +
}}
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{{dcl|num=2|since={{cpp/std|{{#var:cont}}}}|
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const_reference back() const;
 +
}}
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}}
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{{dcl end}}
  
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Returns reference to the last element in the container.  
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Returns a reference to the last element in the container.
  
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<!-- ======== -->
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Calling {{tt|back}} on an empty container causes [[cpp/language/ub|undefined behavior]].
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{{params}}
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{{param none}}
+
  
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<!-- ======== -->
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===Parameters===
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{{returns}}
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(none)
  
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reference to the last element
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===Return value===
 +
Reference to the last element.
  
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<!-- ======== -->
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===Complexity===
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{{complex}}
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Constant.
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{{complex constant}}
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<!-- ======== -->
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===Notes===
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{{see also}}
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For a non-empty container {{tt|c}}, the expression {{c|c.back()}} is equivalent to {{c|*std::prev(c.end())}}.
 +
 
 +
===Example===
 +
{{example
 +
|code=
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#include <cassert>
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#include <{{#var:cont}}>
 +
 
 +
int main()
 +
{
 +
    std::{{#var:cont}}<char{{#switch:{{#var:cont}}|inplace_vector|array=, 4}}> letters{'a', 'b', 'c', 'd'};
 +
    assert(letters.back() == 'd');
 +
}
 +
}}
  
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{{dcl list begin}}
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===See also===
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{{dcl list template | cpp/container/dcl list front |{{{1|}}}}}
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{{dsc begin}}
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{{dcl list end}}
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{{dsc inc|cpp/container/dsc front|{{#var:cont}}}}
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{{dsc inc|cpp/container/dsc rbegin|{{#var:cont}}}}
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{{dsc inc|cpp/container/dsc end|{{#var:cont}}}}
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{{dsc end}}

Latest revision as of 15:30, 15 August 2024

 
C++
 
Containers library
 
std::vector
Member types
Member functions
Non-member functions
(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)
Deduction guides(C++17)
 
reference back();
 (1) (constexpr since C++20)
const_reference back() const;
 (2) (constexpr since C++20)

Returns a reference to the last element in the container.

Calling back on an empty container causes undefined behavior.

Contents

[edit] Parameters

(none)

[edit] Return value

Reference to the last element.

[edit] Complexity

Constant.

[edit] Notes

For a non-empty container c, the expression c.back() is equivalent to *std::prev(c.end()).

[edit] Example

Run this code
#include <cassert>
#include <vector>
 
int main()
{
    std::vector<char> letters{'a', 'b', 'c', 'd'};
    assert(letters.back() == 'd');
}

[edit] See also

 access the first element
(public member function of std::vector<T,Allocator>) [edit]
(C++11)
 returns a reverse iterator to the beginning
(public member function of std::vector<T,Allocator>) [edit]
(C++11)
 returns an iterator to the end
(public member function of std::vector<T,Allocator>) [edit]
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