Definition mutexPCMMix := PCMMixin joinC joinA unitL validL valid_unit.Canonical mutexPCM := Eval hnf in PCM mutex mutexPCMMix.Definition mutexCPCMMix := CPCMMixin joinmK.Canonical mutexCPCM := Eval hnf in CPCM mutex mutexCPCMMix.

Lemma unitb (x : mutex) : reflect (x = Unit) (if x is nown then true else false).