2-dimensional data structures

[Diez B. Roggisch]

Diez B. Roggisch schrieb:
> The question is not so much which region a give square is in, but more 
> which square contains which fields. If we assume that you number your 
> squares row-wise (top-left zero, top-right 3, bottom-right 9), this 
> function computes the field indices that a given square is composed of:

I'm confusing squares with fields here. What I meant by a square here is 
the 3x3 region, of which 9 exist. Each has 3x3=9 cells.

Diez