There was an interesting vector (prevector). All the operators are overloaded so that they can be used like “std :: vector”.
Its content was to reduce the overhead of small arrays.
Actually, when the “prevector” was applied to the blockchain script, it was confirmed that overhead was reduced because many small arrays such as 8 bytes were generated in this part. This speeds up transaction validation.
We are working on development around here and around “Segwit”.