Dictionary De - En
De - Es
De - Pt| English Dictionary: Regular Expression | by the DICT Development Group |
| 1 result for Regular Expression | |
| From The Free On-line Dictionary of Computing (15Feb98) [foldoc]: | |
|
regular expression 1. card} patterns used by {Unix} utilities such as {grep}, {sed} and {awk} and editors such as {vi} and {Emacs}. These use conventions similar to but more elaborate than those described under {glob}. A regular expression is a sequence of characters with the following meanings: An ordinary character (not one of the special characters discussed below) matches that character. A backslash (\) followed by any special character matches the special character itself. The special characters are: "." matches any character except NEWLINE; "RE*" (where the "*" is called the "{Kleene star}") matches zero or more occurrences of RE. If there is any choice, the longest leftmost matching string is chosen, in most regexp {flavour}s. "^" at the beginning of an RE matches the start of a line and "$" at the end of an RE matches the end of a line. [string] matches any one character in that string. If the first character of the string is a "^" it matches any character (except NEWLINE, in most regexp {flavour}s) and the remaining characters in the string. "-" may be used to indicate a range of consecutive ASCII characters. \( RE \) matches whatever RE matches and \n, where n is a digit, matches whatever was matched by the RE between the nth \( and its corresponding \) earlier in the same RE. In many flavours ( RE ) is used instead of \( RE \) The concatenation of REs is a RE that matches the concatenation of the strings matched by each RE. \< matches the beginning of a word and \> matches the end of a word. In many flavours of regexp, \> and \< are replaced by "\b", the special character for "word boundary". RE\{m\} matches m occurences of RE. RE\{m,\} matches m or more occurences of RE. RE\{m,n\} matches between m and n occurences. The exact details of how regexp will work in a given application vary greatly from flavour to flavour. A comprehensive survey of regexp flavours is found in Friedl 1997 (see below). [Jeffrey E.F. Friedl, "{Mastering Regular Expressions(http://enterprise.ic.gc.ca/~jfriedl/regex/index.html)}, O'Reilly, 1997.] 2. Any description of a {pattern} composed from combinations of {symbols} and the three {operators}: Concatenation - pattern A concatenated with B matches a match for A followed by a match for B. Or - pattern A-or-B matches either a match for A or a match for B. Closure - zero or more matches for a pattern. The earliest form of regular expressions (and the term itself) were invented by mathematician {Stephen Cole Kleene} in the mid-1950s, as a notation to easily manipulate "regular sets", formal descriptions of the behaviour of {finite state machines}, in {regular algebra}. [S.C. Kleene, "Representation of events in nerve nets and finite automata", 1956, Automata Studies. Princeton]. [J.H. Conway, "Regular algebra and finite machines", 1971, Eds Chapman & Hall]. [Sedgewick, "Algorithms in C", page 294]. (1997-08-03) | |
