Game of Life rules using switch statement.

Hi could someone please help me write out the game of life rules using switch statement. i know how to do it using if else if (which is all i can find on internet) but there aren't any that use switch. is it possible to use switch? are there any advantages?

say the number of neighbours is called counts. what would I call the new count (i.e how would i update the world?)

would it be:

switch n

case 1 counts= 1, newcount=0??

obviously not thats way to easy

Answer 1

[Geoff Hayes]

Josh - from Game of Life, there are four rules that need to be applied given the state of the cell, three of which are appropriate if the cell is live and one for when the cell is dead. So you have two "objects" to consider - the state of the cell and the rule to apply. Typically, I would use a switch statement only if I had one object (or its state) to be concerned with. In this case, you could use a switch statement on the state of the cell and then, if needed, use a switch statement on the neighbours. Something like

 switch isCellAlive

     case true

         switch numNeighbours

             case {0,1}
                 % live cell has fewer than two neighbours and so dies

             case {2,3}
                 % live cell has 2 0r 3 neighbours and so lives

             otherwise
                 % live cell dies due to over-population
         end

     case false

         if numNeighbours == 3
            % dead cell becomes live
         end
 end

Note that isCellAlive indicates the state of the cell (live or dead, true or false) and that numNeighbours indicates the number of live cells or neighbours.

So are there any advantages to using a switch in the above? I'm not sure. It does work because we only have a small set of integers that are appropriate for each of the cases (0 or 1, or 2 or 3). If you had larger ranges (say all positive integers between 1 and 25) then an if condition would be easier to use than doing case {1,2,3,4,etc.}. I think that the above code is as readable this way or if we were to use an if/elseif block.

Answer 2

[John D'Errico]

Personally, I'd use conv2. What happens if you use the convolution kernel

K = [1 1 1;1 0 1;1 1 1];

1. A live cell will die if it has less than 2 or more than 3 live neighbors.

2. A dead cell is born if it has exactly 3 neighbors.

If the above rules are not met, then the cell stays in the same state it was in before.

Thus, something vaguely like this:

count = conv2(M,K,'same');
born = (M == 0) & (count == 3);
dies = (M == 1) & ((count < 2) | (count > 3));
M(born) = 1;
M(dies) = 0;

Now, just repeat until you get bored, by wrapping a loop around the code fragment above.

You can see one iteration work as follows:

M = double(rand(6) > .5)
M =
     0     1     1     0     1     0
     1     0     1     0     1     0
     1     0     1     1     1     1
     1     1     1     0     0     0
     1     1     1     0     0     1
     0     0     1     0     1     1

count = conv2(M,K,'same')
count =
     2     3     2     4     1     2
     2     6     4     7     4     4
     3     7     4     5     3     2
     4     7     5     5     4     3
     3     6     4     4     3     2
     2     4     2     3     2     2

born = (M == 0) & (count == 3)
born =
     0     0     0     0     0     0
     0     0     0     0     0     0
     0     0     0     0     0     0
     0     0     0     0     0     1
     0     0     0     0     1     0
     0     0     0     1     0     0

dies = (M == 1) & ((count < 2) | (count > 3))
dies =
     0     0     0     0     1     0
     0     0     1     0     1     0
     0     0     1     1     0     0
     1     1     1     0     0     0
     0     1     1     0     0     0
     0     0     0     0     0     0
M(born) = 1;
M(dies) = 0;

M
M =
     0     1     1     0     0     0
     1     0     0     0     0     0
     1     0     0     0     1     1
     0     0     0     0     0     1
     1     0     0     0     1     1
     0     0     1     1     1     1