| slovo | definícia |
regular expression
(encz) | regular expression,regulární výraz [it.] |
regular expression
(foldoc) | regular expression
RE
1. (regexp, RE) One of the {wild
card} patterns used by Perl and other languages, following
Unix utilities such as grep, sed, and awk and editors
such as vi and Emacs. Regular expressions use conventions
similar to but more elaborate than those described under
glob. A regular expression is a sequence of characters with
the following meanings (in Perl, other flavours vary):
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 RE is any
regular expression and 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.
"^" 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.
[CHARS] matches any one of the characters in CHARS. If the
first character of the string is a "^" it matches any
character except the remaining characters in the string (and
also usually excluding newline). "-" 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. Many flavours
use \(RE\) instead of just (RE).
The concatenation of REs is a RE that matches the
concatenation of the strings matched by each RE. RE1 | RE2
matches whatever RE1 or RE2 matches.
\< matches the beginning of a word and \> matches the end of a
word. Many flavours use "\b" instead as 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.
Other flavours use RE\\M\\ etc.
Perl provides several "quote-like" operators for writing
REs, including the common // form and less common ??.
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].
(2015-04-30)
|
| | podobné slovo | definícia |
regular expression converter
(foldoc) | CONVERT
REC
Regular Expression Converter
1. (Or "REC", "Regular Expression Converter") A
string processing language that combined the {pattern
matching} and transformation operations of COMIT with the
recursive data structures of Lisp.
["Convert", A. Guzman et al, CACM 9(8):604-615, Aug 1966].
2. An early language to convert programs and data from one
language to another.
["CONVERT Manual", OLI Systems Inc, Oct 1976].
(2007-02-05)
|
|