proper support for "isabelle update -D DIR": avoid accidental exclusion of select_dirs (amending e5dafe9e120f);
section \<open>Basic combinatorics in Isabelle/HOL (and the Archive of Formal Proofs)\<close>
theory Combinatorics
imports
Transposition
Stirling
Permutations
List_Permutation
Multiset_Permutations
Cycles
Perm
Orbits
begin
end