Open Scope Z_scope.
(** bug 4132: omega was using "simpl" either on whole equations, or on delimited but wrong spots. This was leading to unexpected reductions when one atom (here [b]) is an evaluable reference instead of a variable. *)

Lemma foo
(x y x' zxy zxy' z : Z)
(b := 5)
(Ry : - b <= y < b)
(Bx : x' <= b)
(H : - zxy' <= zxy)
(H' : zxy' <= x') : - b <= zxy.