Module Type HasSgn (Import Z : ZAxiomsMiniSig').
Parameter Inline sgn : t -> t.

Axiom sgn_null : forall n, n==0 -> sgn n == 0.
Axiom sgn_pos : forall n, 0<n -> sgn n == 1.
Axiom sgn_neg : forall n, n<0 -> sgn n == -1.