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How to parse regular expressions to achieve string-related operations, in view of this problem, this article introduces the corresponding analysis and solutions in detail, hoping to help more partners who want to solve this problem to find a more simple and feasible method.

Regular expressions implement string-related operations mainly to anchor the beginning and end of a string, so what is the specific operation process? What should I pay attention to? Let's take a look at the specific operation:

Unlike normal regular expression symbols, anchoring does not match any characters. Instead, they match the position before or after the character. "^" matches the position in front of a line of string * characters. Will match the an in the string "abc". Will not match any characters in "abc".

Similarly, $matches the position after a character in a string. So match c in "abc".

Application of anchoring string by ◆ regular expression

It is important to use anchoring when validating user input in a programming language. If you want to verify that the user's input is an integer, use.

In user input, there are often extra leading or closing spaces. You can use and to match leading spaces or closing spaces.

◆ regular expression implements string anchoring using "^" and "$" as the beginning and end of a line

If you have a string that contains multiple lines. For example: "first line\ n\ rsecond line" (where\ n\ r represents a new line character). It is often necessary to process each line separately instead of the entire string. As a result, almost all regular expression engines provide an option to extend the meaning of these two anchors. "^" matches the start position of the string (before f) and the position after each new line character (between\ n\ r and s). Similarly, $matches the end of the string (after an e) and before each new line character (between e and\ n\ r).

In .NET, when you use the following code, you will define the position before and after the anchor matches each new line character: Regex.Match ("string", "regex", RegexOptions.Multiline)

Application: string str = Regex.Replace (Original, "^", ">", RegexOptions.Multiline)-">" will be inserted at the beginning of each line.

◆ regular expression implements absolute anchoring of string

Matches only the start position of the entire string and only the end position of the entire string. Even if you use "multiline mode", and never match new line characters.

Even if\ Z and $only match the end of the string, there is still an exception. If the string ends with a new line character,\ Z and $will match the position in front of the new line character instead of the * * face of the entire string. This "improvement" was introduced by Perl and followed by many regular expression implementations, including Java,.NET. If applied to "joe\ n", the matching result is "joe" instead of "joe\ n".

This is the answer to the question about how to parse the regular expression to realize the string operation. I hope the above content can be of some help to you, if you still have a lot of doubts to be solved, you can follow the industry information channel for more related knowledge.

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