From Graph Drawing, which is a relative light academic book:
Algorithm 9.1 Coffman-Graham-Layering has two phases; the first orders the vertices, and the second assigns vertices to layers. The algorithm uses an order defined on finite sets of positive integers as follows. If S is a finite set of positive integers, then let maxS) denote the largest element of S.
Then S < T if either:
• S = 0 and T ‡ 0, or
• S ‡D, T # 0, and maxS) < maxT), or
• S + D, T # 0, max(S) = max (T), and S - {max(S)} < T - {max (T)}.
This is the first time T is mentioned in the chapter. It’s not mentioned again in the rest of the chapter. What is it?? Why does it matter?!
I bet there is some sort of convention that explains it that I have never heard of.