| 释义 |
ˈpush-down, n. and a.
Also pushdown.
[f. vbl. phr. to push down: see push v. 1 b.]
A. n. Aeronaut. A manœuvre in which an aircraft in level flight loses altitude and resumes level flight.
1938[see pull-up 3 a].
B. adj.
1. Computers and Linguistics. Being or pertaining to a linear store or list that receives and loses items at one end only, the first to be removed on any occasion being always the last to have been added.
196112th Symp. Appl. Math. 104 These problems seem amenable to solution by the application of techniques based on the use of what some computer people have come to call a ‘pushdown’ store. 1963N. Chomsky in R. D. Luce Handbk. Math. Psychol. II. 343 Evidently pushdown storage is an appropriate device for accepting (generating) languages..which have..nesting of units (phrases) within other units, that is, the kind of recursive property that..we called self-embedding. 1963IEEE Trans. Electronic Computers XII. 872 A ‘push-down’ list is one that is manipulated in a last-in, first-out manner. 1967D. G. Hays Introd. Computational Linguistics ii. 31 The importance of pushdown storage lies in the fact that it has exactly enough power to deal with context-free languages. 1972R. Quirk et al. Gram. Contemp. Eng. xi. 736 The wh-element can be fronted from a position in a clause subordinate to the wh-clause (a pushdown wh-element); for example the informal: I don't remember which shelf he told me I was to fetch it from.
2. That may be or is designed to be pushed down.
1977Custom Car Nov. 18/1 The Escort has sprouted chrome push-down bonnet catches. |