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Regular expressions are particularly useful for defining filters. Regular expressions contain a series of characters that define a pattern of text to be matched—to make a filter more specialized, or general. For example, the regular expression ^AL[.]* searches for all items beginning with AL.
If you want to match for the actual '+', '. ' etc characters, add a backslash( \ ) before that character. This will tell the computer to treat the following character as a search character and consider it for matching pattern. Example : \d+[\+-x\*]\d+ will match patterns like "2+2" and "3*9" in "(2+2) * 3*9".
The regexp-match-positions function takes a regexp pattern and a text string, and it returns a match if the regexp matches (some part of) the text string, or #f if the regexp did not match the string. A successful match produces a list of index pairs.
RegExp Object A regular expression is a pattern of characters. The pattern is used to do pattern-matching "search-and-replace" functions on text. In JavaScript, a RegExp Object is a pattern with Properties and Methods.
Switch-case statement works like if-elseif.
As well as you can use regex for if-elseif, you can also use it in switch-case.
if (preg_match('/John.*/', $name)) {
// do stuff for people whose name is John, Johnny, ...
}
can be coded as
switch $name {
case (preg_match('/John.*/', $name) ? true : false) :
// do stuff for people whose name is John, Johnny, ...
break;
}
Hope this helps.
No or only limited. You could for example switch for true:
switch (true) {
case $a == 'A':
break;
case preg_match('~~', $a);
break;
}
This basically gives you an if-elseif-else statement, but with syntax and might of switch (for example fall-through.)
Yes, but you should use this technique to avoid issues when the switch argument evals to false:
switch ($name) {
case preg_match('/John.*/', $name) ? $name : !$name:
// do stuff
}
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