Difference between revisions of "cpp/container/map/insert"
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− | {{cpp/container/map/title | insert}} | + | {{cpp/container/map/title|insert}} |
{{cpp/container/map/navbar}} | {{cpp/container/map/navbar}} | ||
{{dcl begin}} | {{dcl begin}} | ||
− | {{dcl | num=1 | | + | {{dcl|num=1| |
std::pair<iterator, bool> insert( const value_type& value ); | std::pair<iterator, bool> insert( const value_type& value ); | ||
}} | }} | ||
− | {{dcl | num=2 | since=c++11 | | + | {{dcl|num=2|since=c++11| |
template< class P > | template< class P > | ||
std::pair<iterator, bool> insert( P&& value ); | std::pair<iterator, bool> insert( P&& value ); | ||
}} | }} | ||
− | {{dcl | num=3 | since=c++17 | | + | {{dcl|num=3|since=c++17| |
std::pair<iterator, bool> insert( value_type&& value ); | std::pair<iterator, bool> insert( value_type&& value ); | ||
}} | }} | ||
− | {{dcl rev | + | {{dcl rev multi|num=4|until1=c++11| |
− | + | |dcl1= | |
− | iterator insert( iterator | + | iterator insert( iterator pos, const value_type& value ); |
+ | |dcl2= | ||
+ | iterator insert( const_iterator pos, const value_type& value ); | ||
}} | }} | ||
− | + | {{dcl|num=5|since=c++11| | |
− | + | ||
− | + | ||
− | + | ||
− | {{dcl | num=5 | since=c++11 | | + | |
template< class P > | template< class P > | ||
− | iterator insert( const_iterator | + | iterator insert( const_iterator pos, P&& value ); |
}} | }} | ||
− | {{dcl | num=6 | since=c++17 | | + | {{dcl|num=6|since=c++17| |
− | iterator insert( const_iterator | + | iterator insert( const_iterator pos, value_type&& value ); |
}} | }} | ||
− | {{dcl | num=7 | | + | {{dcl|num=7| |
template< class InputIt > | template< class InputIt > | ||
void insert( InputIt first, InputIt last ); | void insert( InputIt first, InputIt last ); | ||
}} | }} | ||
− | {{dcl | num=8 | since=c++11 | | + | {{dcl|num=8|since=c++11| |
void insert( std::initializer_list<value_type> ilist ); | void insert( std::initializer_list<value_type> ilist ); | ||
}} | }} | ||
− | {{dcl | num=9 | since=c++17 | | + | {{dcl|num=9|since=c++17| |
insert_return_type insert( node_type&& nh ); | insert_return_type insert( node_type&& nh ); | ||
}} | }} | ||
− | {{dcl | num=10 | since=c++17 | | + | {{dcl|num=10|since=c++17| |
− | iterator insert( const_iterator | + | iterator insert( const_iterator pos, node_type&& nh ); |
}} | }} | ||
{{dcl end}} | {{dcl end}} | ||
Line 44: | Line 42: | ||
Inserts element(s) into the container, if the container doesn't already contain an element with an equivalent key. | Inserts element(s) into the container, if the container doesn't already contain an element with an equivalent key. | ||
− | @1-3@ Inserts {{ | + | @1-3@ Inserts {{c|value}}. |
+ | @@ Overload {{v|2}} is equivalent to {{c|emplace(std::forward<P>(value))}} and only participates in overload resolution if {{c|1=std::is_constructible<value_type, P&&>::value == true}}. | ||
− | @4-6@ Inserts {{ | + | @4-6@ Inserts {{c|value}} in the position as close as possible to the position just prior to {{c|pos}}. |
+ | @@ Overload {{v|5}} is equivalent to {{c|emplace_hint(hint, std::forward<P>(value))}} and only participates in overload resolution if {{c|1=std::is_constructible<value_type, P&&>::value == true}}. | ||
− | @7@ Inserts elements from range {{ | + | @7@ Inserts elements from range {{range|first|last}}. {{cpp/container/lwg2488-note}} |
− | @8@ Inserts elements from initializer list {{ | + | @8@ Inserts elements from initializer list {{c|ilist}}. {{cpp/container/lwg2488-note}} |
− | {{cpp/container/ | + | {{cpp/container/node handle insert desc|map|9|10}} |
− | {{cpp/container/ | + | {{cpp/container/note iterator invalidation|map|insert}} |
===Parameters=== | ===Parameters=== | ||
{{par begin}} | {{par begin}} | ||
− | {{par | | + | {{par|pos|iterator to the position before which the new element will be inserted}} |
− | {{par | value | element value to insert}} | + | {{par|value|element value to insert}} |
− | {{par | first, last | range of elements to insert}} | + | {{par|first, last|range of elements to insert}} |
− | {{par | ilist | initializer list to insert the values from}} | + | {{par|ilist|initializer list to insert the values from}} |
− | {{par | nh | a compatible [[cpp/container/node_handle|node handle]]}} | + | {{par|nh|a compatible [[cpp/container/node_handle|node handle]]}} |
{{par hreq}} | {{par hreq}} | ||
− | {{par req named | InputIt | InputIterator}} | + | {{par req named|InputIt|InputIterator}} |
− | {{par end}} | + | {{par end}} |
===Return value=== | ===Return value=== | ||
− | @1-3@ | + | @1-3@ {{cpp/container/return iterator pair||pair}} |
− | @4-6@ | + | @4-6@ {{cpp/container/return iterator pair}} |
− | @7 | + | @7,8@ (none) |
− | {{cpp/container/ | + | {{cpp/container/node handle insert return|map|9|10}} |
===Exceptions=== | ===Exceptions=== | ||
Line 83: | Line 83: | ||
@1-3@ Logarithmic in the size of the container, {{tt|O(log(size()))}}. | @1-3@ Logarithmic in the size of the container, {{tt|O(log(size()))}}. | ||
− | + | @4-6@ Amortized constant if the insertion happens in the position just {{rev inl|until=c++11|''after''}}{{rev inl|since=c++11|''before''}} {{c|pos}}, logarithmic in the size of the container otherwise. | |
− | + | ||
− | @4-6@ Amortized constant if the insertion happens in the position just ''after'' | + | |
− | }} | + | |
− | {{rev | since=c++11 | | + | |
− | + | ||
− | + | ||
− | + | ||
− | @7 | + | @7,8@ {{tt|O(N·log(size() + N))}}, where {{tt|N}} is the number of elements to insert. |
@9@ Logarithmic in the size of the container, {{tt|O(log(size()))}}. | @9@ Logarithmic in the size of the container, {{tt|O(log(size()))}}. | ||
− | @10@ Amortized constant if the insertion happens in the position just ''before'' | + | @10@ Amortized constant if the insertion happens in the position just ''before'' {{c|pos}}, logarithmic in the size of the container otherwise. |
===Notes=== | ===Notes=== | ||
− | {{cpp/container/ | + | {{cpp/container/hinted insert note|4-6}} |
===Example=== | ===Example=== | ||
{{example | {{example | ||
− | + | |code= | |
#include <iomanip> | #include <iomanip> | ||
#include <iostream> | #include <iostream> | ||
#include <map> | #include <map> | ||
#include <string> | #include <string> | ||
− | |||
using namespace std::literals; | using namespace std::literals; | ||
template<typename It> | template<typename It> | ||
− | void | + | void print_insertion_status(It it, bool success) |
{ | { | ||
− | std::cout << "Insertion of " << it->first << (success ? " succeeded\n" : " failed\n"); | + | std::cout << "Insertion of " << it->first |
+ | << (success ? " succeeded\n" : " failed\n"); | ||
} | } | ||
int main() | int main() | ||
{ | { | ||
− | std::map<std::string, float> | + | std::map<std::string, float> heights; |
// Overload 3: insert from rvalue reference | // Overload 3: insert from rvalue reference | ||
− | const auto [it_hinata, success] = | + | const auto [it_hinata, success] = heights.insert({"Hinata"s, 162.8}); |
− | + | print_insertion_status(it_hinata, success); | |
{ | { | ||
// Overload 1: insert from lvalue reference | // Overload 1: insert from lvalue reference | ||
− | const auto [it, success2] = | + | const auto [it, success2] = heights.insert(*it_hinata); |
− | + | print_insertion_status(it, success2); | |
} | } | ||
{ | { | ||
// Overload 2: insert via forwarding to emplace | // Overload 2: insert via forwarding to emplace | ||
− | const auto [it, success] = | + | const auto [it, success] = heights.insert(std::pair{"Kageyama", 180.6}); |
− | + | print_insertion_status(it, success); | |
} | } | ||
− | |||
{ | { | ||
// Overload 6: insert from rvalue reference with positional hint | // Overload 6: insert from rvalue reference with positional hint | ||
− | const std::size_t n = std::size( | + | const std::size_t n = std::size(heights); |
− | const auto it = | + | const auto it = heights.insert(it_hinata, {"Azumane"s, 184.7}); |
− | + | print_insertion_status(it, std::size(heights) != n); | |
} | } | ||
{ | { | ||
// Overload 4: insert from lvalue reference with positional hint | // Overload 4: insert from lvalue reference with positional hint | ||
− | const std::size_t n = std::size( | + | const std::size_t n = std::size(heights); |
− | const auto it = | + | const auto it = heights.insert(it_hinata, *it_hinata); |
− | + | print_insertion_status(it, std::size(heights) != n); | |
} | } | ||
{ | { | ||
// Overload 5: insert via forwarding to emplace with positional hint | // Overload 5: insert via forwarding to emplace with positional hint | ||
− | const std::size_t n = std::size( | + | const std::size_t n = std::size(heights); |
− | const auto it = | + | const auto it = heights.insert(it_hinata, std::pair{"Tsukishima", 188.3}); |
− | + | print_insertion_status(it, std::size(heights) != n); | |
} | } | ||
− | auto node_hinata = | + | auto node_hinata = heights.extract(it_hinata); |
− | std::map<std::string, float> | + | std::map<std::string, float> heights2; |
// Overload 7: insert from iterator range | // Overload 7: insert from iterator range | ||
− | + | heights2.insert(std::begin(heights), std::end(heights)); | |
// Overload 8: insert from initializer_list | // Overload 8: insert from initializer_list | ||
− | + | heights2.insert({{"Kozume"s, 169.2}, {"Kuroo", 187.7}}); | |
− | + | ||
// Overload 9: insert node | // Overload 9: insert node | ||
− | const auto status = | + | const auto status = heights2.insert(std::move(node_hinata)); |
− | + | print_insertion_status(status.position, status.inserted); | |
− | node_hinata = | + | node_hinata = heights2.extract(status.position); |
{ | { | ||
// Overload 10: insert node with positional hint | // Overload 10: insert node with positional hint | ||
− | const std::size_t n = std::size( | + | const std::size_t n = std::size(heights2); |
− | const auto it = | + | const auto it = heights2.insert(std::begin(heights2), std::move(node_hinata)); |
− | + | print_insertion_status(it, std::size(heights2) != n); | |
} | } | ||
− | |||
// Print resulting map | // Print resulting map | ||
std::cout << std::left << '\n'; | std::cout << std::left << '\n'; | ||
− | for (const auto& [name, height] : | + | for (const auto& [name, height] : heights2) |
std::cout << std::setw(10) << name << " {{!}} " << height << "cm\n"; | std::cout << std::setw(10) << name << " {{!}} " << height << "cm\n"; | ||
} | } | ||
− | | output= | + | |output= |
Insertion of Hinata succeeded | Insertion of Hinata succeeded | ||
Insertion of Hinata failed | Insertion of Hinata failed | ||
Line 200: | Line 190: | ||
Tsukishima {{!}} 188.3cm | Tsukishima {{!}} 188.3cm | ||
}} | }} | ||
+ | |||
+ | ===Defect reports=== | ||
+ | {{dr list begin}} | ||
+ | {{dr list item|wg=lwg|dr=233|std=C++98|before={{c|pos}} was just a hint, it could be totally ignored|after=the insertion is required to<br>be as close as possible to the<br>position just prior to {{c|pos}}}} | ||
+ | {{dr list item|wg=lwg|dr=264|std=C++98|before=the complexity of overload {{v|7}} was required to be linear if<br>the range {{range|first|last}} is sorted according to {{tt|Compare}}|after=removed the linear requirement<br>in this special case}} | ||
+ | {{dr list item|wg=lwg|dr=316|std=C++98|before=in the return value of overload {{v|1}}, it was not specified<br>which {{c/core|bool}} value indicates a successful insertion|after=success is<br>indicated by {{c|true}}}} | ||
+ | {{dr list item|wg=lwg|dr=2005|std=C++11|before=overloads {{v|2,5}} were poorly described|after=improved the description}} | ||
+ | {{dr list end}} | ||
===See also=== | ===See also=== | ||
{{dsc begin}} | {{dsc begin}} | ||
− | {{dsc inc | cpp/container/dsc emplace |map}} | + | {{dsc inc|cpp/container/dsc emplace|map}} |
− | {{dsc inc | cpp/container/dsc emplace_hint |map}} | + | {{dsc inc|cpp/container/dsc emplace_hint|map}} |
− | {{dsc inc | cpp/container/dsc insert_or_assign |map}} | + | {{dsc inc|cpp/container/dsc insert_or_assign|map}} |
+ | {{dsc inc|cpp/iterator/dsc inserter}} | ||
{{dsc end}} | {{dsc end}} | ||
{{langlinks|de|es|fr|it|ja|pt|ru|zh}} | {{langlinks|de|es|fr|it|ja|pt|ru|zh}} |
Latest revision as of 10:35, 15 March 2024
std::pair<iterator, bool> insert( const value_type& value ); |
(1) | |
template< class P > std::pair<iterator, bool> insert( P&& value ); |
(2) | (since C++11) |
std::pair<iterator, bool> insert( value_type&& value ); |
(3) | (since C++17) |
(4) | ||
iterator insert( iterator pos, const value_type& value ); |
(until C++11) | |
iterator insert( const_iterator pos, const value_type& value ); |
(since C++11) | |
template< class P > iterator insert( const_iterator pos, P&& value ); |
(5) | (since C++11) |
iterator insert( const_iterator pos, value_type&& value ); |
(6) | (since C++17) |
template< class InputIt > void insert( InputIt first, InputIt last ); |
(7) | |
void insert( std::initializer_list<value_type> ilist ); |
(8) | (since C++11) |
insert_return_type insert( node_type&& nh ); |
(9) | (since C++17) |
iterator insert( const_iterator pos, node_type&& nh ); |
(10) | (since C++17) |
Inserts element(s) into the container, if the container doesn't already contain an element with an equivalent key.
[
first,
last)
. If multiple elements in the range have keys that compare equivalent, it is unspecified which element is inserted (pending LWG2844).No iterators or references are invalidated. If the insertion is successful, pointers and references to the element obtained while it is held in the node handle are invalidated, and pointers and references obtained to that element before it was extracted become valid.(since C++17)
Contents |
[edit] Parameters
pos | - | iterator to the position before which the new element will be inserted |
value | - | element value to insert |
first, last | - | range of elements to insert |
ilist | - | initializer list to insert the values from |
nh | - | a compatible node handle |
Type requirements | ||
-InputIt must meet the requirements of LegacyInputIterator.
|
[edit] Return value
insert_return_type
with the members initialized as follows:
- If nh is empty,
inserted
is false,position
is end(), andnode
is empty. - Otherwise if the insertion took place,
inserted
is true,position
points to the inserted element, andnode
is empty. - If the insertion failed,
inserted
is false,node
has the previous value of nh, andposition
points to an element with a key equivalent to nh.key().
[edit] Exceptions
This section is incomplete Reason: cases 7-10 |
[edit] Complexity
O(log(size()))
.O(N·log(size() + N))
, where N
is the number of elements to insert.O(log(size()))
.[edit] Notes
The hinted insert (4-6) does not return a boolean in order to be signature-compatible with positional insert on sequential containers, such as std::vector::insert. This makes it possible to create generic inserters such as std::inserter. One way to check success of a hinted insert is to compare size()
before and after.
[edit] Example
#include <iomanip> #include <iostream> #include <map> #include <string> using namespace std::literals; template<typename It> void print_insertion_status(It it, bool success) { std::cout << "Insertion of " << it->first << (success ? " succeeded\n" : " failed\n"); } int main() { std::map<std::string, float> heights; // Overload 3: insert from rvalue reference const auto [it_hinata, success] = heights.insert({"Hinata"s, 162.8}); print_insertion_status(it_hinata, success); { // Overload 1: insert from lvalue reference const auto [it, success2] = heights.insert(*it_hinata); print_insertion_status(it, success2); } { // Overload 2: insert via forwarding to emplace const auto [it, success] = heights.insert(std::pair{"Kageyama", 180.6}); print_insertion_status(it, success); } { // Overload 6: insert from rvalue reference with positional hint const std::size_t n = std::size(heights); const auto it = heights.insert(it_hinata, {"Azumane"s, 184.7}); print_insertion_status(it, std::size(heights) != n); } { // Overload 4: insert from lvalue reference with positional hint const std::size_t n = std::size(heights); const auto it = heights.insert(it_hinata, *it_hinata); print_insertion_status(it, std::size(heights) != n); } { // Overload 5: insert via forwarding to emplace with positional hint const std::size_t n = std::size(heights); const auto it = heights.insert(it_hinata, std::pair{"Tsukishima", 188.3}); print_insertion_status(it, std::size(heights) != n); } auto node_hinata = heights.extract(it_hinata); std::map<std::string, float> heights2; // Overload 7: insert from iterator range heights2.insert(std::begin(heights), std::end(heights)); // Overload 8: insert from initializer_list heights2.insert({{"Kozume"s, 169.2}, {"Kuroo", 187.7}}); // Overload 9: insert node const auto status = heights2.insert(std::move(node_hinata)); print_insertion_status(status.position, status.inserted); node_hinata = heights2.extract(status.position); { // Overload 10: insert node with positional hint const std::size_t n = std::size(heights2); const auto it = heights2.insert(std::begin(heights2), std::move(node_hinata)); print_insertion_status(it, std::size(heights2) != n); } // Print resulting map std::cout << std::left << '\n'; for (const auto& [name, height] : heights2) std::cout << std::setw(10) << name << " | " << height << "cm\n"; }
Output:
Insertion of Hinata succeeded Insertion of Hinata failed Insertion of Kageyama succeeded Insertion of Azumane succeeded Insertion of Hinata failed Insertion of Tsukishima succeeded Insertion of Hinata succeeded Insertion of Hinata succeeded Azumane | 184.7cm Hinata | 162.8cm Kageyama | 180.6cm Kozume | 169.2cm Kuroo | 187.7cm Tsukishima | 188.3cm
[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 233 | C++98 | pos was just a hint, it could be totally ignored | the insertion is required to be as close as possible to the position just prior to pos |
LWG 264 | C++98 | the complexity of overload (7) was required to be linear if the range [ first, last) is sorted according to Compare
|
removed the linear requirement in this special case |
LWG 316 | C++98 | in the return value of overload (1), it was not specified which bool value indicates a successful insertion |
success is indicated by true |
LWG 2005 | C++11 | overloads (2,5) were poorly described | improved the description |
[edit] See also
(C++11) |
constructs element in-place (public member function) |
(C++11) |
constructs elements in-place using a hint (public member function) |
(C++17) |
inserts an element or assigns to the current element if the key already exists (public member function) |
creates a std::insert_iterator of type inferred from the argument (function template) |