| ordered(ixs, x), n < # ixs ⊦ ixs = [], ordered(ixs[n], x) |
∀ x, n. ordered(ixs0, x) ∧ n < # ixs0 → ixs0 = [] ∨ ordered(ixs0[n], x), ordered(ix + ixs0, x), n < #(ix + ixs0) ⊦ ix + ixs0 = [], ordered((ix + ixs0)[n], x)
[Concretesimprules((Csimpgen(illist freely generated by [], +;)))]