Effects: A directive that informs a
vector
of a planned change in size, so that it can manage the storage allocation accordingly
. After
reserve(),
capacity()
is greater or equal to the argument of
reserve
if reallocation happens; and equal to the previous value of
capacity()
otherwise
. Reallocation happens at this point if and only if the current capacity is less than the
argument of
reserve(). If an exception is thrown
other than by the move constructor of a non-
Cpp17CopyInsertable type,
there are no effects
.