fact: Fixpoint decB {n} : BITS n -> BITS n := if n is _.+1 then fun p => let (p,b) := eta_expand (splitlsb p) in if b then joinlsb (p, false) else joinlsb (decB p, true) else fun _ => nilB.
imports: mathcomp.ssreflect.ssreflect mathcomp(ssrfun ssrbool eqtype ssrnat seq tuple) spec