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Difference between revisions of "cpp/iterator/front inserter"

From cppreference.com
< cpp‎ | iterator
m (r2.7.3) (Robot: Adding de, es, fr, it, ja, pt, ru, zh)
m (→‎Synopsis: {{mark constexpr since c++20}})
 
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{{cpp/title|front_inserter}}
 
{{cpp/title|front_inserter}}
 
{{cpp/iterator/navbar}}
 
{{cpp/iterator/navbar}}
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{{ddcl list begin}}
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{{ddcl|header=iterator|notes={{mark constexpr since c++20}}|
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{{ddcl list header | iterator}}
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{{ddcl list item |
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template< class Container >
 
template< class Container >
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std::front_insert_iterator<Container> front_inserter( Container& c);
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std::front_insert_iterator<Container> front_inserter( Container& c );
 
}}
 
}}
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{{ddcl list end}}
 
  
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{{tt|front_inserter}} is a convenience function template that constructs a {{c|std::front_insert_iterator}} for the container {{tt|c}} with the type deduced from the type of the argument.
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{{tt|front_inserter}} is a convenience function template that constructs a {{lc|std::front_insert_iterator}} for the container {{c|c}} with the type deduced from the type of the argument.
  
 
===Parameters===
 
===Parameters===
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{{param list begin}}
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{{par begin}}
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{{param list item | c | container that supports a {{tt|push_front}} operation}}
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{{par|c|container that supports a {{tt|push_front}} operation}}
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{{param list end}}
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{{par end}}
  
 
===Return value===
 
===Return value===
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A {{c|std::front_insert_iterator}} which can be used to add elements to the beginning of the container {{tt|c}}
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A {{lc|std::front_insert_iterator}} which can be used to add elements to the beginning of the container {{c|c}}.
  
 
===Possible implementation===
 
===Possible implementation===
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{{eq fun | 1=
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{{eq fun|1=
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template< class Container >
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template<class Container>
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std::front_insert_iterator<Container> front_inserter( Container& c)
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std::front_insert_iterator<Container> front_inserter( Container& c )
 
{
 
{
 
     return std::front_insert_iterator<Container>(c);
 
     return std::front_insert_iterator<Container>(c);
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===Example===
 
===Example===
 
{{example
 
{{example
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|
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|code=
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| code=
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#include <iostream>
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#include <deque>
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#include <algorithm>
 
#include <algorithm>
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#include <deque>
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#include <iostream>
 
#include <iterator>
 
#include <iterator>
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#include <vector>
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int main()
 
int main()
 
{
 
{
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     std::deque<int> v{1,2,3,4,5,6,7,8,9,10};
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     std::vector<int> v{1, 2, 3, 4, 5};
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     std::fill_n(std::front_inserter(v), 3, -1);
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     std::deque<int> d;
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     for(int n : v)
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    std::copy(v.begin(), v.end(), std::front_inserter(d));
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     for (int n : d)
 
         std::cout << n << ' ';
 
         std::cout << n << ' ';
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    std::cout << '\n';
 
}
 
}
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| output=
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|output=
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-1 -1 -1 1 2 3 4 5 6 7 8 9 10
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5 4 3 2 1  
 
}}
 
}}
  
 
===See also===
 
===See also===
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{{dcl list begin}}
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{{dsc begin}}
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{{dcl list template | cpp/iterator/dcl list front_insert_iterator}}
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{{dsc inc|cpp/iterator/dsc front_insert_iterator}}
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{{dcl list template | cpp/iterator/dcl list back_inserter}}
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{{dsc inc|cpp/iterator/dsc back_inserter}}
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{{dcl list template | cpp/iterator/dcl list inserter}}
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{{dsc inc|cpp/iterator/dsc inserter}}
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{{dcl list end}}
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{{dsc end}}
  
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[[de:cpp/iterator/front inserter]]
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{{langlinks|de|es|fr|it|ja|pt|ru|zh}}
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[[es:cpp/iterator/front inserter]]
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[[fr:cpp/iterator/front inserter]]
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[[it:cpp/iterator/front inserter]]
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[[ja:cpp/iterator/front inserter]]
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[[pt:cpp/iterator/front inserter]]
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[[ru:cpp/iterator/front inserter]]
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[[zh:cpp/iterator/front inserter]]
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Latest revision as of 14:54, 3 October 2023

 
C++
 
Iterator library
Iterator concepts
Iterator primitives
Algorithm concepts and utilities
Indirect callable concepts
Common algorithm requirements
(C++20)
(C++20)
(C++20)
Utilities
(C++20)
Iterator adaptors
Range access
(C++11)(C++14)
(C++14)(C++14)  
(C++11)(C++14)
(C++14)(C++14)  
(C++17)(C++20)
(C++17)
(C++17)
 
Defined in header <iterator>
template< class Container >
std::front_insert_iterator<Container> front_inserter( Container& c );
 (constexpr since C++20)

front_inserter is a convenience function template that constructs a std::front_insert_iterator for the container c with the type deduced from the type of the argument.

Contents

[edit] Parameters

c - container that supports a push_front operation

[edit] Return value

A std::front_insert_iterator which can be used to add elements to the beginning of the container c.

[edit] Possible implementation

template<class Container>
std::front_insert_iterator<Container> front_inserter( Container& c )
{
    return std::front_insert_iterator<Container>(c);
}

[edit] Example

Run this code
#include <algorithm>
#include <deque>
#include <iostream>
#include <iterator>
#include <vector>
 
int main()
{
    std::vector<int> v{1, 2, 3, 4, 5};
    std::deque<int> d;
    std::copy(v.begin(), v.end(), std::front_inserter(d));
    for (int n : d)
        std::cout << n << ' ';
    std::cout << '\n';
}

Output: 

5 4 3 2 1

[edit] See also

 iterator adaptor for insertion at the front of a container
(class template) [edit]
creates a std::back_insert_iterator of type inferred from the argument
(function template) [edit]
creates a std::insert_iterator of type inferred from the argument
(function template) [edit]
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