Suppose I want to store some data (a non-negative integer) related to an "event" involving two entities. It occurs to me that the way to do it is using a 2-d array, like a table:
a b c a 1 b 2 0 c 5
in the event 'b-a' the data is 2, and in the event 'c-a' is 5, etc.
Now, I need to be able to differentiate between 0 and 'no data'. I know I could use a number like -1, but this would affect arithmetic operations on the array, and also I need that indexing one such location with no data returns an empty array.
Is it possible to do this with the standard array class?