fact: Definition star (p1 p2 : Pred U) : Pred U := [Pred h | exists h1 h2, [ /\ h = h1 \+ h2, h1 \In p1 & h2 \In p2] ].
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq bigop fintype finset) pcm(options axioms prelude seqperm pred seqext)