== case x1 of
== Rnone => false
== Rplus(left,right)=>rec1,rec2.false
== Rinit(loc,T,x,v)=> false
== Rframe(loc,T,x,L)=> false
== Rsframe(lnk,tag,L)=> false
== Reffect(loc,ds,knd,T,x,f)=> false
== Rsends(ds,knd,T,l,dt,g)=> false
== Rpre(loc,ds,a,T,P)=> true
== Raframe(loc,k,L)=> false
== Rbframe(loc,k,L)=> false
== Rrframe(loc,x,L)=> false