/** \mainpage rrq C hacks: Vectors And Such

This software is an implementation platform for vector based
representations.

- \ref itemkeyfun is an implementation of an abstracted type notion
  that is focussed on what the \ref hashvector needs in terms of
  callbacks for its separation between the hash management
  functionality and the contained items. This name is choosen so as to
  avoid some connotations common to the term "type".

- \ref array and \ref vector are two implementations of an abstract
  array notion using an indexing tree of 16 and 256 pointers
  respectively. The indexing tree is balanced into levels matching to
  the needs of the vector size. When the size of a vector is changed
  then indexing levels are added or removed as needed. However
  indexing pages are allocated on a needs basis. The level 0 indexing
  pages hold the actual data as void* pointers

- \ref hasharray and \ref hashvector are two implementations of an
  abstract hashtable using \ref array and \ref vector as backing store
  respectively. It also uses the \ref itemkeyfn type abstraction of
  items being compunded as pairs of key and payload. This separates
  the hashing code from the type abstraction.

\subsubsection s0 itemkeyfun actualizations

- \ref integeritem is an plain actualization of an itemkeyfun record
  for integer items other than 0 and 1, i.e. where the void* slots of
  a tuple are reinterpreted as 64-bit integers rather than "item
  pointers".

\note Note that a hashvector cannot directly contain integer items
  since 0 and 1 are treated as indicating unused and holed slots.

- stringitem is a plain actualization of an itemkeyfun record for
  null-terminated character strings.

- tupleschema is a specialization of the itemkeyfun type scheme
  intended for tuple items that are arrays of items that are further
  type via itemkeyfun records. A tupleschema actualization includes
  the applicable arity and an array of pointers to itemkeyfun
  actualizations that declare the itemkeyfun types of the parts
  (columns).

*/