| ⊦ a ' + x = y + b ' ∧ y ≠ [] → a ∈ y ∧ b ∈ x |
a ' + x = y + b ', a ∈ y ∨ a = b, b = a ∨ b ∈ x ⊦ y = [], a ∈ y ∧ b ∈ x
Used simplifier rules: in-14: ⊦ a ' + x = y → a ∈ y;%a: ⊦ (x + y) + z = x + y + z;%in-15: ⊦ x + a ' = y → a ∈ y;%in-append: ⊦ a ∈ x + y ↔ ¬ ¬(a ∈ x ∨ a ∈ y);%in-17: ⊦ a ∈ b ' ↔ a = b;%in-rec: ⊦ a ∈ b ' + x ↔ ¬ ¬(a = b ∨ a ∈ x);