When used outside brackets, the hyphen is a literal. If you wrote the range as, the browser would see that as an error. Note: a range must always be in ascending order. To shorten things, we can use a hyphen ( -) to specify a range of characters, in this case 0 through 9. We can do that with the group -which gets pretty tedious when the phone numbers comprise of 11 digits. For example, to test for a Canadian long-distance phone number (for example, if you're caling someone outside the province you're calling from, you're calling long-distance), the first thing we need to do is to test if each character is a number. Sometimes, you want a rather large group of characters that can be arranged into a sequence. Let's see how that works (the script used for this page isalmost identical to that above save for the regex): xpression The next 9 characters are xpression in that order, with that case, and no spaces between them. This is how this regex works: The first character is either E or e. What I can do in this instance is immediately follow the group of characters with the rest of the word (which is a literal), resulting in the regex xpression. In fact, it is uncommon for such a grammatical unit to not match this particular string of words is an illustration of that, and as such was hard to writ e. >A regex consisting of only would match almost any sentence in the English language. Switching the order ( ) would work just as well. So to check for either a lower- or upper-case E, you would group them together like this. The two meta characters to do that are: This ends a group of characters. One thing you can do is check for both the upper- and lower-case e, then the rest of the word-but first, you have to group those two characters together so that they're treated as options for one character. For example, if you tried to test for expression, but a certain string contained Expression instead, there would be no match remember, regular expressions are case sensitive, The regex must be made into a regex object before these functions can use it.A regex can also check to see if one of a group of characters is in it. However, these functions take the regex object as an argument and not just the regex. Commonly used functions for C++ regular expressions, are: regex_search(), regex_match() and regex_replace(). The regular expression uses patterns to match substrings in the target sequence string. The function returns a new string, which is the target but having the replacement. The first argument of the function is the target, the second is the regex object, and the third is the replacement string. The regex_replace() function, as coded here, replaces all the matches. String newStr = regex_replace (str, regex ( "man" ), "woman" ) The programmer may want to know if this target has “goat” or “rabbit” or “pig”. Matching AlternationĬonsider the following target string in the computer. There is a nuance at the last match – see later. It matches the one ‘e’ in “set”, the two ‘e’s in “sheep”, the three ‘e’s in “sheeep”, and three ‘e’s in “sheeeep”. X ” matches nothing in “dig”, which has no ‘e’. X +: means match 'x' 1 or more times, i. X *: means match 'x' 0 or more times, i.