一句话:研究仅由 B 组合子构成的 B-项在重复右应用下是否循环,给出等式公理化与检测循环的规范表示算法。
本文研究仅由 B 组合子(B ≡ λfgx. f(g x))构成的 B-项的一个性质:对 B-项重复进行右应用时是否会出现循环。作者通过可靠且完备的等式公理化来刻画 B-项具有或不具有该循环性质的条件。文中给出了具有循环性质的 B-项实例,并证明不具有该性质的 B-项有无穷多个。此外,文章还引入 B-项规范表示的一个新性质,该表示可用于检测循环,或等价地证明循环性质,并给出有效算法。本文为 LMCS 期刊版本。
$B$-terms are built from the $B$ combinator alone defined by $B\equiv\lambda fgx. f(g~x)$, which is well known as a function composition operator. This paper investigates an interesting property of $B$-terms, that is, whether repetitive right applications of a $B$-term cycles or not. We discuss conditions for $B$-terms to have and not to have the property through a sound and complete equational axiomatization. Specifically, we give examples of $B$-terms which have the cyclic property and show that there are infinitely many $B$-terms which do not have the property. Also, we introduce another interesting property about a canonical representation of $B$-terms that is useful to detect cycles, or equivalently, to prove the cyclic property, with an efficient algorithm.Comment: Journal version in Logical Methods in Computer Science. arXiv admin note: substantial text overlap with arXiv:1703.10938