ANN: xtable (extended table library)

[Dirk Laurie <dirk.laurie@...>]

`xtable` is a library of generic functions for table manipulation,
designed and written by Dirk Laurie and John Hind.

The project started as a drop-in replacement for the standard table
library, incorporating a selection of extra features that have on
occasion been requested on this list (e.g. multiple insert/remove;
count-backwards negative indices; list integrity maintenance).
The authors gradually realized that no two Lua users can be made to
agree on just which extra features are desirable, and moved to a model
of C core functions with a Lua top layer.

The standard table library is fast mainly for the following reasons:

  - table accessess are done by `lua_rawgeti` and `lua_rawseti`,
    which directly call a C function with the indices already
    available as C integers;
  - temporary values are kept on the stack;
  - loops are coded directly in C.

Accordingly, the `xtable` core C routines perform tasks that exploit
these techniques. They do only essential parameter checking and do not
supply default table limits (neither 1 nor `#tbl`). The intention is
that users can easily implement their own add-ons directly in Lua
without sacrificing the speed of the C core.

The library contains two sublibraries: `xtable.block` and `xtable.tuple`.

`xtable.block` is designed to be a suitable `__index` for a table
that will be used mainly as an array. Every function has the same
first three arguments `tbl,a,b` and operates on the elements from
`tbl[a]` to `tbl[b]`, where decreasing keys are taken when `a>b`.
The functions `get`, `set`, `move` and `trisect` are provided in
the C core; `concat`, `insert`, `remove` and `sort`, which in various
ways offer more than their namesakes from the standard library, are
provided in the Lua top layer.

`xtable.tuple` is a suite of routines that take `...` arguments.
The functions `keep`, `map` and `collect` are  provided in
the C core; `cache` and `iter` are provided in the Lua top layer.
The intention is not to provide full tuple support, but merely
to provide some essential services for routines that are based on
the block routines.

The library is well documented, including markdown source, an HTML
version and interactive help.

You can download a zip file containing the library from
<https:github.com/dlaurie/xtable/zip>, or clone the repository
(some files may be newer in that case).  It is released under the
same license as Lua.