cs249 lecture notes, Fall 2001
Week 11, Thursday

http://rocky.wellesley.edu/cs249/code/protolife.m

Life is the top-level function.  There are many annoying
things about generating figures in MATLAB.  One of them
is that there seem to be some options you can set once
and some that you have to reset after every iteration.
If there is order in this madness, I don't discern it.

function life
size = 105;
A = zeros (size, size);
A = center (A, pattern);
c = [ 1 1 1; 0 0 0 ];
colormap (c);                % you can set this ahead of time
for i=1:1000
   A = update (A);
   pcolor (A);
   shading flat;             % but this only after the fact
   pause (0.01);             % we need this to update the figure
end


You will fill in the body of update as homework.

function C = update (A)
% compute the next iteration of life using matrix operations
C = A;

We will fill in the body of updateIter today in lab.

function B = updateIter (A)
% compute the next iteration of life using for loops
B = A;


You wrote a version of copymatrix on the Quiz.

function result = center (A, B)
% copy the matrix B into the middle of matrix a
r = round ((size(A,1) - size(B,1)) / 2);
c = round ((size(A,2) - size(B,2)) / 2);
result = copymatrix (A, B, r, c);


function result = copymatrix (A, B, r, c)
% copy the matrix B into matrix A at the location r, c
height = size (B,1);
width  = size (B,2);
A(r:r+height-1,c:c+width-1) = B;
result = A;

The function pattern is from a web page that provides a number of
Life entities.


A program development plan
--------------------------

1) Decide what functions you need and what their interfaces
   are.  For this project I have done that.

2) Write outlines of each of the functions.  Usually the outlines
   contain a single line of code that assigns something simple to
   the output variable.

3) Develop and test each function in isolation:

   a) adding a small number of lines at a time

   b) add print and display commands to generate something
      visible you can use to test the function

4) assemble the functions into a working whole

   a) sometimes as you go along, you change the interfaces to
      some of the functions.  When you do this, remember to
      update all the places where the function is called.