Set: pp::colors
  Set: pp::unicode
  Assumed: g
  Assumed: a
  Assumed: b
  Assumed: H1
  Assumed: H2
  Proved: T1
Axiom H2 : (g a) > 0
Theorem T1 : (g b) > 0 := Subst (λ x : ℤ, if ((g x) ≤ 0) ⊥ ⊤) H2 H1