PascGalois JE Help: 2-D Cellular Automata Update Rule Tab


Setting the Update Rule

Setting the update rule for 2-D automata is similar to that for the 1-D automata. As with the seed the only difference is that you are working with levels of grids instead of rows. The Update Rule tab looks like,

The rule is any valid group theoretic expression that uses variable names for the group elements and integers for the exponents. Juxtaposition for the group operation is not recognized, you must use a * to denote a group operation. Powers are denoted by ^ and any negative powers must be put in parentheses. Variable names can be any string of letters. Numbers, underscores and special characters are not permitted. For example, the following are legitimate update rule expressions, a*b, a^2*b, b*a*b^(-1), a*b*a^(-1)*b^(-1), and a^3*b^(-4). The following are not legitimate expressions, a^2b and a*b*a^-1*b^-1.

The update grid is how you tell the program where to get the elements that are to be used in the update formula. There must be one and only one X in the entire grid and it must be on the last level of the grid, but it may be in any position on that level. The position of the X tells the program that this is the cell to be updated. The other entries are names of variables used in the update rule. When the program generates its data it will start at the X and substitute the respective cell entries in for the corresponding variables in the formula to determine the value of the new cell.

The Update Rule Toolbar

There are eight tools for the update rule tab.


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