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This article introduces the knowledge of "how to use Clear11 regular expression Library". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Basic usage

Code description

The most basic use, of course, is to define a regular expression and then use it.

The code uses regex to define a regular expression r that describes the word "test". It is a word because the metacharacter'\ b'is placed at both ends of "test" to match the beginning or end of the word. Because we code in the C++ environment, the actual code is "\ b".

Output result

Although there is a testing in the example sentence, a test is found correctly.

Use subexpressions

Regular expressions often contain subexpressions, that is, the part of an expression that is surrounded by parentheses.

Code description

The regular expression defined in the code contains two subexpressions that match the file name and the extension, respectively.

The matching result is also slightly different. When including a subexpression, use str (0) to get the whole of the matching result, use str (1) to be the first subexpression, and so on.

Output result

Matching iterator

In actual development, repeated lookups often occur, and sregex_iterator is provided in the expression library to deal with this problem.

Code description

First define the regular expression as a word that starts with test. Then define two sregex_iterator. One is used for matching search, and the other is used for finished judgment.

Output result

As you can see, the match happened twice. But it is a pity that all the matching parts are displayed. Take it easy.

Subexpression + iterator

Take a look at an example of repeating the different filenames of a lookup statement.

Code description

The code combines the techniques of subexpressions and iterators.

Output result

That's what it looks like.

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