Compiling ALPACA to Javascript

This document describes a functionality of which the ALPACA reference implementation is capable, but is not a part of the ALPACA specification.

The reference implementation is able to compile an ALPACA description to a set of Javascript functions which, when called, will evolve a form for that cellular automaton.

These functions assume each generation is stored in a data structure called a playfield, which has two methods:

• get(x, y): retrieve the name of the state at (x, y)
• map(new_pf, fun, min_x, min_y, max_x, max_y): apply fun to every cell of the playfield to obtain a new playfield

In addition, if the ALPACA description supplies an initial playfield, the Javascript compiler will generate two var variables:

• defaultCell, which is a string that contains the name of the state that cells that have never been modified assume by default
• initialPlayfield, which is an array of triples (3-element arrays); each triple consists of x co-ordinate, y co-ordinate, and state name.

This interface can be used by additional Javascript code to evolve the automaton that the ALPACA description describes.