Hasse diagram (awaiting review)

If $(S, \leq)$ is a finite partially ordered set, then a Hasse diagram for $S$ is a representation of $S$ in the plane where

• there is one node for each element of $S$
• there is an edge connecting $s_1$ and $s_2$ if $s_1$ is maximal in $\leq$ for $\{s\in S \mid s < s_2\}$, or vice versa
• if $s_1$ is connected to $s_2$ by an edge and $s_1 < s_2$, then $s_2$ is higher in the plane in the sense of having a larger "$y$-coordinate"