核心概念
コンテキストフリー言語におけるポンピング補題の重要性と応用に焦点を当てる。
统计
2N < z ≤22N, always from PL, the language is infinite (because it contains infinite strings uviwxiy), and so, as previously, it is enough to consider derivations of length no geater than 22(N+1) −1, whose number is upper bounded by |P| · 22N+1.
Let L be a CFL; we can suppose {ǫ} ̸= L ̸= ∅otherwise the thesis is trivially verified.
引用
"Given a CFL it is decidable to establish if it is (1) empty, or (2) infinite, and so if it is (3) finite and if (4) a given word belongs to it or not." - Theorem 5.3