| ki ∈ keyset(kar, n0) ↔ (∃ m. m < n0 ∧ ki = kar[m]), n0 < # kar, ki = kar[n0] ∨ ki ∈ keyset(kar, n0) ⊦ ∃ m. ¬ n0 < m ∧ ki = kar[m] |
ki ∈ keyset(kar, n0) ↔ (∃ m. m < n0 ∧ ki = kar[m]), ki = kar[n0], n0 < # kar ⊦ ∃ m. ¬ n0 < m ∧ ki = kar[m]
ki ∈ keyset(kar, n0) ↔ (∃ m. m < n0 ∧ ki = kar[m]), n0 < # kar, ki ∈ keyset(kar, n0) ⊦ ∃ m. ¬ n0 < m ∧ ki = kar[m]