| ⊦ # ar = n0 + n1 ↔ (∃ ar0, ar1. ar = ar0 + ar1 ∧ # ar0 = n0 ∧ # ar1 = n1) |
⊦ #(ar0 + ar1) = # ar0 + # ar1
⊦ (ar + ar0) + ar1 = ar + ar0 + ar1
# ar = n0 + n1 ⊦ ∃ ar0, ar1. ar = ar0 + ar1 ∧ # ar0 = n0 ∧ # ar1 = n1
Used simplifier rules: append-len: ⊦ #(ar0 + ar1) = # ar0 + # ar1;%append-a: ⊦ (ar + ar0) + ar1 = ar + ar0 + ar1;%c: ⊦ m + n = n + m; from specification nat-basic%a: ⊦ (m + n0) + n1 = m + n0 + n1; from specification nat-basic% ⊦ m + n = m + n0 ↔ n = n0; (s)