fact: Definition variation a b f s := let F := f \o nth b (a :: s) in \sum_(0 <= n < size s) `|F n.+1 - F n|%R.
imports: mathcomp(all_ssreflect ssralg ssrint ssrnum finmap) mathcomp(matrix interval zmodp vector fieldext falgebra) mathcomp(mathcomp_extra boolp classical_sets functions) mathcomp(cardinality) ereal reals signed topology prodnormedzmodule normedtype derive sequences real_interval HB(structures)