## 6 de enero de 2016

### A fixing in a fence

— You know, a fence in lattice theory, more precisely an $n$-element fence in lattice theory, is an ordered set $\{x_1,\ldots,x_n\}$ in which $x_1$ is greater than $x_2$, $x_2$ less than $x_3$, $x_3$ greater than the next one, etc., and $x_n$ greater or less than $x_{n-1}$ depending whether $n$ is odd or even, or $x_1$ less than $x_2$, $x_2$ greater than $x_3$, etc., and its Hasse diagram looks like a zigzag.
— I see. So a defense is quite the opposite, and its Hasse diagram looks like a zagzig.
— No offense, but no!
— Exactly! (You're so emphatic, I like that.)