避免“索引超出矩阵尺寸”的功能

Question

I have problem with MATLAB - or at least I cannot solve it at the moment and if I look after that specific error message than I get very complicated examples. Brought to its total base, my problem looks as follows:

I have to program a Connect-Four game. The game field is initalized with zeros that way:

    Field = zeros([6 7]);

Later on, I have to check for the win condition. However, if I do something like

    if GameField(7, 7) == xxx

then it obviously fails, as the game field has just six columns. The exact error message is 'Index exceeds matrix dimensions' - and I can definitely understand why this is.

Is there any function, which can help me to avoid that error (in a way like try-catch in programming languages). I know for example that there is a function called exists , but this does only work with variables, etc. - but not with matrix dimensions. Using the length() -function would be quite tricky when dealing with diagonal values. I'm actually looking for a function (where I do not know the name) that works the following

    if valueExists(GameField(7, 7))
      %do something
    else
      %do something other
    end

Answer 1

You know the size of the field, store that in a variable called fieldSize .

fieldSize = [6 7];

Thus, you can conveniently initialize the field as

Field = zeros(fieldSize);

Next, when you want to perform checks, for example whether the value to the bottom right of the current position is 1, you can always check against fieldSize first

currentPosition = [1 7];
bottomRight = currentPosition - [1 1];
if any(bottomRight < 1 | bottomRight > fieldSize)
   % do not check b/c out of field
else
   % perform check
end

Alternatively, you could optimize your search strategy so that you never look outside the field in the first place. For example a diagonal of four going bottom left to top right can never start in columns 5:7.