22 Containers library [containers]

22.3 Sequence containers [sequences]

22.3.8 Class template deque [deque]

22.3.8.3 Capacity [deque.capacity]

void resize(size_type sz);
Expects: T is Cpp17MoveInsertable and Cpp17DefaultInsertable into *this.
Effects: If sz < size(), erases the last size() - sz elements from the sequence.
Otherwise, appends sz - size() default-inserted elements to the sequence.
void resize(size_type sz, const T& c);
Expects: T is Cpp17CopyInsertable into *this.
Effects: If sz < size(), erases the last size() - sz elements from the sequence.
Otherwise, appends sz - size() copies of c to the sequence.
void shrink_to_fit();
Expects: T is Cpp17MoveInsertable into *this.
Effects: shrink_­to_­fit is a non-binding request to reduce memory use but does not change the size of the sequence.
Note
:
The request is non-binding to allow latitude for implementation-specific optimizations.
— end note
 ]
If the size is equal to the old capacity, or if an exception is thrown other than by the move constructor of a non-Cpp17CopyInsertable T, then there are no effects.
Complexity: If the size is not equal to the old capacity, linear in the size of the sequence; otherwise constant.
Remarks: If the size is not equal to the old capacity, then invalidates all the references, pointers, and iterators referring to the elements in the sequence, as well as the past-the-end iterator.