| flatten(val ++ val1 ++ val2) = val3 ++ val0, ∀ val. ∃ val1, val3. flatten(val ++ val2) = val1 ++ val3, ∀ val. ∃ val3, val2. flatten(val ++ val1) = val3 ++ val2 ⊦ ∃ val0, val3. flatten(val ++ val1 ++ val2) = val0 ++ val3 |
[[CONCRETESIMPRULES : ()], [EXTRATERMS : (val3, val0)]]