fact: Definition trunc_def x n : n%:R <= x < n.+1%:R -> trunc x = n := @ssrnum.Num.Theory.mc_2_0.trunc_def R x n.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop order ssralg poly ssrnum ssrint)