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(* 02110-1301 USA                                                     *)
Unset Standard Proposition Elimination Names.

Theorem switch_addenv :
forall (G : env) (p q : PP) (t1 t2 : type),
p <> q -> eqvenv (addenv (addenv G p t1) q t2) (addenv (addenv G q t2) p t1).