reserve x, y, z, s for ExtReal;
reserve i, j for Integer;
reserve n, m for Nat;
reserve x, y, v, u for ExtInt;

theorem
  -infty < x
  proof
    x is Integer or x = +infty by Def1;
    then x in REAL or x = +infty by XREAL_0:def 1;
    hence thesis by XXREAL_0:12;
  end;
