| ⊦ ri |> key0 |> key1 = ri |> key0, key0 < key1 |
⊦ ri = ri0 ↔ (∀ key. (key ∈ ri ↔ key ∈ ri0) ∧ (key ∈ ri → ri[key] = ri0[key]))
⊦ key0 < key1, ∀ key. (key ∈ ri |> key0 |> key1 ↔ key ∈ ri |> key0) ∧ (key ∈ ri |> key0 |> key1 → (ri |> key0 |> key1)[key] = (ri |> key0)[key])
Used terms: ri |> key0, ri |> key0 |> key1