| y ⊆m y0, x ⊆m x0 ⊦ y + x ⊆m x0 + y0 |
x ⊆m x0, a + y1 ⊆m y0, ∀ y0, x, x0. y1 ⊆m y0 ∧ x ⊆m x0 → y1 + x ⊆m x0 + y0 ⊦ (a + y1) + x ⊆m x0 + y0
Used simplifier rules: subempty: ⊦ [] ⊆m x;%subapp-02: ⊦ x ⊆m x0 → x ⊆m x0 + y;%list freely generated by [], +;;% ⊦ [] + x = x; (s)%a: ⊦ (x + y) + z = x + y + z; from specification list