Deque - how come "reserve" doesn't exist?
c++, stl
Solution
Increasing the capacity of a `std::vector` can be costly. When a `vector` outgrows its reserved space, the entire contents of the vector must be copied (or moved) to a larger reserve.
It is specifically because std::vector resizing can be costly that `vector::reserve()` exists. `reserve()` can prepare a `std::vector` to anticipate reaching a certain size without exceeding its capacity.
Conversely, a `deque` can always add more memory without needing to relocate the existing elements. If a `std::deque` could `reserve()` memory, there would be little to no noticeable benefit.
Problem
The standard STL vector container has a "reserve" function to reserve uninitialized memory that can be used later to prevent reallocations. How come that the other deque container hasn't it?