| ⊦ dups(x), ¬ dups(x + set2list(s)) ∧ ¬ dups(x + set2list(s0)), ∃ a. a ∈ x ∧ (a ∈ s ∨ a ∈ s0) |
⊦ dups(x + y) ↔ dups(x) ∨ dups(y) ∨ (∃ a. a ∈ x ∧ a ∈ y)
⊦ dups(x), ¬(dups(x) ∨ dups(set2list(s)) ∨ (∃ a. a ∈ x ∧ a ∈ set2list(s))) ∧ ¬ dups(x + set2list(s0)), ∃ a. a ∈ x ∧ (a ∈ s ∨ a ∈ s0)
Used terms: set2list(s), x