| ∃ y, z. y0 = y + (a + z) ⊦ a = a0, ∃ y, z. y0 + a0 ' = y + a ' + z ∧ z ≠ [] |
⊦ a = a0, ∃ y0, z0. y + (a ' + z) + a0 ' = y0 + a ' + z0 ∧ z0 ≠ []
Used simplifier rules: a: ⊦ (x + y) + z = x + y + z; from specification list%c: ⊦ a + x = a ' + x; from specification list