| # y < # filter(rmdup(x), y) ⊦ filter(rmdup(x), y) = [] |
∀ y. # y < # filter(rmdup(x0), y) → filter(rmdup(x0), y) = [], # y < # filter(rmdup(a + x0), y) ⊦ filter(rmdup(a + x0), y) = []
Used simplifier rules: filt-e: ⊦ filter([], y) = [];%list freely generated by [], +;;%rmdup-e: ⊦ rmdup([]) = []; from specification list-dup