bitfield-eca
============

Version 0.0.1 (January 7, 2017)

eca is a collection of algorithms that implement Elementary Cellular Automata.

Algorithms
----------

Elementary Cellular Automaton is a one-dimensional two-state CA, where the state 
of a cell in the next generation depends only on the current state of the cell 
and its two immediate neighbors. The state of each cell is represented by one bit in a bit array. The rule of transformation is represented by "Wolfram code".

An important convention is that bits are numbered and showed from right to left. This means that bit 0 is the rightmost.

Example: Rule 30

|       current state       | 111 | 110 | 101 | 100 | 011 | 010 | 001 | 000 |
+---------------------------+-----+-----+-----+-----+-----+-----+-----+-----+
| new state for center cell |  0  |  0  |  0  |  1  |  1  |  1  |  1  |  0  |

center' = left XOR [ center OR right ]

The boolean formulae are taken from:
  * Stephen Wolfram, A New Kind of Science, p. 884
  * Evangelos Georgiadis, A Note on Minimal Boolean Formula Size of 
One-Dimensional Cellular Automata, Journal of Cellular Automata. 2007, Vol. 2 Issue 4, p. 353

Installation
------------

Please see the file called INSTALL.

Usage
-----

THe 'bitfield-eca' library is an extension to the 'bitfield' library, so in most cases, functions provided by eca are used along with functions from the core.
If bitfield-eca library files are installed system-wide in standard locations, then one needs to (1) include a system version of the header file to the source

#include <bitfield-eca.h>

and (2) add the "-lbitfield-eca -lbitfield" flags to compiler instructions

gcc ... -lbitfield-eca -lbitfield

Alternatively, if bitfield-eca library is integrated into a project, then one needs to (1) include a local version of the header file to the source

#include "PATH_TO_HEADER/bitfield-eca.h"

and (2) add the "-lbitfield-eca -lbitfield" flags, along with the path to the header and path to the library to compiler instructions

gcc ... -I$(PATH_TO_HEADER) -L$(PATH_TO_LIBRARY) -lbitfield-eca -lbitfield

Functions
---------
For function syntax, see "eca.h". For details on every function, see
its manual page.

eca_string() transforms an array of bits by a corresponding Wolfram's rule.

eca_string_ip() transforms an array of bits "in-place".

eca_ring() treats the input array of bits as a ring and transforms it
by a corresponding Wolfram's rule.

eca_ring_ip() treats the input array of bits as a ring and transforms
it "in-place".

Please, see "examples" directory for working examples.

Licensing
---------

bitfield-eca is free software, and is released under the terms of the GNU General 
Public License version 3 or any later version. Please see the file called 
LICENSE.