⊦ H0 = H1 ↔ (∀ r. (r ∈ H0 ↔ r ∈ H1) ∧ (r ∈ H0 → H0[r] = H1[r]))
r ∈ H ⊦ ∀ r0. (r0 ∈ H ↔ r0 ∈ ((H -- r) ++ r)[r, H[r]]) ∧ (r0 ∈ H → H[r0] = ((H -- r) ++ r)[r, H[r]][r0])
Used terms: ((H -- r) ++ r)[r, H[r]], H