proposition: Lemma preimage_abse_pinfty : @abse R @^-1` [set +oo] = [set -oo; +oo].
proof: Proof. by rewrite predeqE => y; split ; move: y => [y//| |]//=; [right | left | case]. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap) mathcomp(mathcomp_extra boolp classical_sets functions) mathcomp(fsbigop cardinality set_interval) reals signed topology constructive_ereal