| ⊦ r = null, r0 = r, r ∈ H, (r1 = r ∨ r1 ≠ r0 ∧ r1 ∈ H → r1 ≠ r0 ∧ (r1 = r ∨ r1 ∈ H)) ∧ (r1 = r ∨ r1 ≠ r0 ∧ r1 ∈ H → (r1 = r ⊃ o;((H -- r0) ++ r)[r1]) = ((H ++ r)[r, o] -- r0)[r1]) |
r1 = r ∨ r1 ≠ r0 ∧ r1 ∈ H ⊦ r = null, r0 = r, r ∈ H, r1 ≠ r0 ∧ (r1 = r ∨ r1 ∈ H)
r1 = r ∨ r1 ≠ r0 ∧ r1 ∈ H ⊦ (r1 = r ⊃ o;((H -- r0) ++ r)[r1]) = ((H ++ r)[r, o] -- r0)[r1], r = null, r0 = r, r ∈ H