fact: Definition itv_decompose i x : Prop := let: Interval l u := i in (match l return Prop with | BSide b lb => lb < x ?<= if b | BInfty b => b end * match u return Prop with | BSide b ub => x < ub ?<= if ~~ b | BInfty b => ~~ b end)%type.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(div fintype bigop order ssralg finset fingroup) mathcomp(ssrnum)