proposition: Lemma int_abs_sig_alt x : { n : N | f n = x } + { n : N | f n = -x }.
proof: Proof. destruct (int_abs_spec x) as [[??]|[??]]; eauto. Qed.
imports: Coq.setoid_ring.Ring MathClasses.interfaces.naturals MathClasses.interfaces.abstract_algebra MathClasses.interfaces.orders MathClasses.orders.nat_int MathClasses.theory.integers MathClasses.theory.rings MathClasses.orders.rings