In the 1980s, programmers could not resist the urge to expand the existing regular expression syntax to make its patterns even more useful-most notably Henry Spencer with his regex library, then Larry Wall with the Perl language, which used then expanded Spencer's library. Naturally, some saw the potential for even more powerful text-matching patterns. These tools made text-matching much easier than the alternative-writing custom parsing programs for each task. In the late 1960s Ken Thompson of Bell Labs wrote them into the editor QED, and in the 1970s they made it into Unix programs and utilities such as grep, sed and AWK. The name of the father of regular expressions (Stephen Kleene) is immortalized in the Kleene star, the small character in A* that tells the engine that the character A must be matched zero or more times. Regular expression engines that conformed to this regularity were called Deterministic Finite Automatons (DFAs). But that one person has a special claim, because a long long time ago (the 1950s, at the dawn of computer science) a regular expression referred to what the mathematician Stephen Kleene described as a regular language, which itself referred to a mathematical property called regularity. What about the hundredth person? Actually, the proportion is probably closer to one in a thousand. Common plurals are regexes, regexps and even regexen (thank you, Larry Wall). Another common abbreviation (which is losing the abbreviation war) is regexp. For them (and for Rex), regex is an abbreviation of regular expression. Nowadays, 99 percent of people who mention regular expressions are really speaking about regex. At this stage, this is a semantic question-it depends on what one means by regular expression.
0 kommentar(er)
