⊦ dups(x + a ' + b ') ↔ dups(x + a '), a = b, b ∈ x
Heuristic simplifier applied rule simplifier
And closed the goal!
Rule argument
Additional information
Used simplifier rules:
f: ⊦ dups(x + a ') ↔ a ∈ x ∨ dups(x);%a: ⊦ (x + y) + z = x + y + z; from specification list% ⊦ a ∈ b ' ↔ a = b; (s)% ⊦ a ∈ x + y ↔ a ∈ x ∨ a ∈ y; (s)