| 释义 |
reachable, a.|ˈriːtʃəb(ə)l|
[f. reach v.1]
†1. Able to reach to. Obs. rare—1.
1633T. Adams Exp. 2 Peter ii. 10 A tower reachable to heaven!
2. a. That may be reached. Also, as n., one who may be reached (in quot. 1974, denoting a person who can be bribed).
1824L. M. Hawkins Mem. II. 5 note, My father..had strong oak shutters put on the outside of all the reachable windows in our house. 1873W. S. Mayo Never Again xvii. 229 If through the sense of smell Her heart were reachable. 1914R. & E. Shackleton Four on Tour in Eng. xviii. 186 Few visitors go to Runnimede [sic], because it has not been a readily reachable place by rail. 1974Publishers Weekly 27 May 31 (Advt.), The secret deals behind the rip-off, put⁓down and sell-out of the American people..to Big Money interests..with the help of the reachables in office! 1978Detroit Free Press 5 Mar. a4/1 Most buds and twigs and other reachable food are gone. If snow is deep enough, deer cannot escape.
b. Math. That may be reached (from a specified point) by passing along the lines of a graph.
1959Sociometry XXII. 143 The matrix M contains all these paths and also a path of length l from each point to itself. Thus each point is reachable from itself. 1965F. Harary et al. Structural Models ii. 43 Point v is reachable from u in a digraph D if and only if there is a sequence from u to v. 1978D. D. S̆iljak Large-Scale Dynamic Syst. iii. 149 A reachable set Vi(vj) of a point vj is a set of points vi reachable from vj.
Hence reachaˈbility Math., the possibility of reaching one point of a graph from another; freq. attrib.
1959Sociometry XXII. 141 We present a logical sequence of theorems that characterize strengthening and weakening group members... We..find it convenient to introduce the concept of the ‘reachability matrix’ of a group. 1965F. Harary et al. Structural Models ii. 43 Reachability is reflexive since every point of V is reachable from itself by a path of length 0. Ibid. 45 The difference between reachability and joining is that in the latter instance we ignore the direction of the lines. Ibid. v. 117 The reachability matrix R(D) whose entries are denoted rij and defined as follows: rij = 1 if vj is reachable from vi; otherwise rij = 0. 1978D. D. S̆iljak Large-Scale Dynamic Syst. iii. 149 The reachability concept of digraphs. |