TAILIEUCHUNG - HandBooks Professional Java-C-Scrip-SQL part 59

Tham khảo tài liệu 'handbooks professional java-c-scrip-sql part 59', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Usage To begin using you need to include the header boost . Regex is one of the two libraries the other one is covered in this book that need to be separately compiled. You ll be glad to know that after you ve built Boostthis is a one-liner from the command promptlinking is automatic for Windows-based compilers anyway so you re relieved from the tedium of figuring out which lib file to use. The first thing you need to do is to declare a variable of type basic_regex. This is one of the core classes in the library and it s the one that stores the regular expression. Creating one is simple just pass a string to the constructor containing the regular expression you want to use. boost regex reg A. This regular expression contains three interesting features of regular expressions. The first is the enclosing of a subexpression within parenthesesthis makes it possible to refer to that subexpression later on in the same regular expression or to extract the text that matches it. We ll talk about this in detail later on so don t worry if you don t yet see how that s useful. The second feature is the wildcard character the dot. The wildcard has a very special meaning in regular expressions it matches any character. Finally the expression uses a repeat called the Kleene star which means that the preceding expression may match zero or more times. This regular expression is ready to be used in one of the algorithms like so bool b boost regex_match This expression could match from A and beyond. reg As you can see you pass the regular expression and the string to be parsed to the algorithm regex_match. The result of calling the function is true if there is an exact match for the regular expression otherwise it is false. In this case the result is false because regex_match only returns true when all of the input data is successfully matched by the regular expression. Do you see why that s not the case for this code Look again at the regular .

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