iterator insert( const_iterator pos, const T& value );
(1) (constexpr since C++20)iterator insert( const_iterator pos, T&& value );
(2) (since C++11)iterator insert( const_iterator pos,
size_type count, const T& value );
template< class InputIt >
iterator insert( const_iterator pos, InputIt first, InputIt last );
Inserts elements at the specified location in the container.
1) Inserts a copy of value before pos.
If any of the following conditions is satisfied, the behavior is undefined:
T
is not CopyAssignable.2) Inserts value before pos, possibly using move semantics.
3) Inserts count copies of the value before pos.
If any of the following conditions is satisfied, the behavior is undefined:
T
is not CopyAssignable.Inserts elements from range
[
first,
last)
before
pos.
This overload has the same effect as overload (3) if InputIt
is an integral type.
This overload participates in overload resolution only if InputIt
satisfies the requirements of LegacyInputIterator.
If any of the following conditions is satisfied, the behavior is undefined:
5) Inserts elements from initializer list ilist before pos.
Equivalent to insert(pos, ilist.begin(), ilist.end()).
If after the operation the new size()
is greater than old capacity()
a reallocation takes place, in which case all iterators (including the end()
iterator) and all references to the elements are invalidated. Otherwise, only the iterators and references before the insertion point remain valid.
1,2) Iterator pointing to the inserted value.
3-5) Iterator pointing to the first element inserted, or pos if no element is inserted.
[edit] ComplexityIf reallocation happens, linear in the number of elements of the vector
after insertion; otherwise, linear in the number of elements inserted plus std::distance(pos, end()).
If an exception is thrown other than by
T
,T
,T
,T
,InputIt
operation,these functions have no effect (strong exception safety guarantee).
If an exception is thrown when inserting a single element at the end, and T
is CopyInsertable into *this or std::is_nothrow_move_constructible<T>::value is true, this function has no effect (strong exception guarantee). Otherwise, if an exception is thrown by the move constructor of a non-CopyInsertable T
, the effects are unspecified.
#include <iostream> #include <iterator> #include <string_view> #include <vector> namespace stq { void println(std::string_view rem, const std::vector<int>& container) { std::cout << rem.substr(0, rem.size() - 2) << '['; bool first{true}; for (const int x : container) std::cout << (first ? first = false, "" : ", ") << x; std::cout << "]\n"; } } int main() { std::vector<int> c1(3, 100); stq::println("1. {}", c1); auto pos = c1.begin(); pos = c1.insert(pos, 200); // overload (1) stq::println("2. {}", c1); c1.insert(pos, 2, 300); // overload (3) stq::println("3. {}", c1); // pos no longer valid, get a new one: pos = c1.begin(); std::vector<int> c2(2, 400); c1.insert(std::next(pos, 2), c2.begin(), c2.end()); // overload (4) stq::println("4. {}", c1); int arr[] = {501, 502, 503}; c1.insert(c1.begin(), arr, arr + std::size(arr)); // overload (4) stq::println("5. {}", c1); c1.insert(c1.end(), {601, 602, 603}); // overload (5) stq::println("6. {}", c1); }
Output:
1. [100, 100, 100] 2. [200, 100, 100, 100] 3. [300, 300, 200, 100, 100, 100] 4. [300, 300, 400, 400, 200, 100, 100, 100] 5. [501, 502, 503, 300, 300, 400, 400, 200, 100, 100, 100] 6. [501, 502, 503, 300, 300, 400, 400, 200, 100, 100, 100, 601, 602, 603][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 149 C++98 overloads (3) and (4) returned nothing returns an iterator LWG 247 C++98 the complexity was only specified for overload (3) specified for all overloads LWG 406 C++98 the strong exception guarantee also applied ifInputIt
operation no guarantee in this case [edit] See also
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