Returns true iff no elements are present.
Push element (struct) value to back of array.
Push element (struct) value to back of array using its data members members.
Index operator.
Slice operator.
Growth factor P/Q. https://github.com/facebook/folly/blob/master/folly/docs/FBVector.md#memory-handling
Use 1.5 like Facebook's fbvector does.
Structure of arrays similar to members of S.