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

From cppreference.com
m (+(since C++11) to array; `constexpr since` to vector)
 
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{{cpp/container/{{{1|}}}/title|back}}
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{{#vardefine:cont|{{{1|vector}}}}}<!--
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{{cpp/container/{{{1|}}}/navbar}}
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-->{{cpp/container/{{#var:cont}}/title|back}}
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{{cpp/container/{{#var:cont}}/navbar}}
 
{{dcl begin}}
 
{{dcl begin}}
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{{#switch:{{{1|}}}|array=
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{{#switch:{{#var:cont}}
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|array=
 
{{dcl|num=1|since=c++11|notes={{mark constexpr since c++17}}|
 
{{dcl|num=1|since=c++11|notes={{mark constexpr since c++17}}|
 
reference back();
 
reference back();
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{{dcl|num=2|notes={{mark constexpr since c++20}}|
 
{{dcl|num=2|notes={{mark constexpr since c++20}}|
 
const_reference back() const;
 
const_reference back() const;
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}}
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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|{{{1|}}}}}|
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{{dcl|num=1|since={{cpp/std|{{#var:cont}}}}|
 
reference back();
 
reference back();
 
}}
 
}}
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{{dcl|num=2|since={{cpp/std|{{{1|}}}}}|
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{{dcl|num=2|since={{cpp/std|{{#var:cont}}}}|
 
const_reference back() const;
 
const_reference back() const;
 
}}
 
}}
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===Example===
 
===Example===
 
{{example
 
{{example
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|The following code uses {{tt|back}} to display the last element of a {{c|std::{{{1}}}<char>}}:
 
 
|code=
 
|code=
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#include <{{{1|}}}>
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#include <cassert>
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#include <iostream>
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#include <{{#var:cont}}>
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+
 
 
int main()
 
int main()
 
{
 
{
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     std::{{{1|}}}<char{{#ifeq:{{{1|}}}|array|, 6}}> letters{'a', 'b', 'c', 'd', 'e', 'f'};
+
     std::{{#var:cont}}<char{{#switch:{{#var:cont}}|inplace_vector|array=, 4}}> letters{'a', 'b', 'c', 'd'};
−
 
+
     assert(letters.back() == 'd');
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     if (!letters.empty())
+
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        std::cout << "The last character is '" << letters.back() << "'.\n";
+
 
}
 
}
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|output=
 
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The last character is 'f'.
 
 
}}
 
}}
  
 
===See also===
 
===See also===
 
{{dsc begin}}
 
{{dsc begin}}
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{{dsc inc|cpp/container/dsc front|{{{1|}}}}}
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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}}}}
 
{{dsc end}}
 
{{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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