diff --git a/hw2.tex b/hw2.tex index 1692fe6..6c6e5a6 100644 --- a/hw2.tex +++ b/hw2.tex @@ -247,6 +247,11 @@ Show that the set of all partitions of a set~$S$ with the refinement relation~$\preceq$ is a lattice. + % Task: Well-founded relation. + \item A poset $\Pair{R, \preceq}$ is \emph{well-founded} if there is no infinite decreasing sequence of elements in the poset, that is, elements $x_1, x_2, \dots, x_n$ such that $\dots \prec x_n \prec \dots \prec x_2 \prec x_1$. + Determine whether the set of strings of lowercase English letters with lexicographic order is well-founded. + + % \item \dots \end{tasks}