| 释义 |
▪ I. digraph1|ˈdaɪgrɑːf, -æ-|
[f. Gr. δι- twice, di-2, + γραϕή writing, etc.]
A group of two letters expressing a simple sound of speech.
a1788T. Sheridan (L.), All improper diphthongs, or, as I have called them, digraphs, are changed into the single vowels which they stand for. 1812J. C. Hobhouse Journey Albania App. 1061 If these combinations of vowels had been distinguished in writing only..their name would have been digraphs, and not dipthongs. 1873Earle Philol. Eng. Tongue §193 He would therefore recognise the consonantal digraphs ch, gh..sh, th, wh, ng, as alphabetic characters. 1877Sweet Phonetics 174 If..we exclude new letters..we are obliged to fall back on digraphs.
▪ II. digraph2 Math.|ˈdaɪgrɑːf, -æ-|
[f. directed ppl. a. + graph n.1]
A graph (sense 1) in which each line has a direction associated with it; a finite, non-empty set of elements together with a set of ordered pairs of these elements.
1955F. Harary in Trans. Amer. Math. Soc. LXXVII. 445 Our object is..to count various kinds of generalizations of graphs. These include directed graphs (digraphs), rooted graphs [etc.]. 1965― Structural Models i. 2 The theory of directed graphs, or more briefly ‘digraphs’ (a term suggested by G. Pólya). 1973C. W. Gear Introd. Computer Sci. vii. 299 A road map in which every road is one-way would be a digraph. 1976Bondy & Murty Graph Theory with Applications x. 171 Every concept that is valid for graphs automatically applies to digraphs too... However, there are many concepts that involve the notion of orientation, and these apply only to digraphs. 1980Sci. Amer. Mar. 18/2 No matter how the arrowheads are placed on a complete digraph, there will always be a directed path that visits each point just once. Such a path is called a Hamiltonian. |