| ∀ ps0, str. # ps0 < # ps → true → #(str + ps0) = # ps0 ⊦ # ps = 0, #(str + ps) = # ps, ps = ∅ |
⊦ ps = ps0 ↔ (∀ p. p ∈ ps ↔ p ∈ ps0)
∀ ps0, str. # ps0 < # ps → true → #(str + ps0) = # ps0 ⊦ #(str + ps) = # ps, # ps = 0, ∀ p. p ∈ ps ↔ p ∈ ∅
Used terms: ∅, ps