std::basic_regex<CharT,Traits>::basic_regex
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basic_regex();
(1)
(since C++11)
explicit basic_regex( const CharT* s,
flag_type f = std::regex_constants::ECMAScript );
(2)
(since C++11)
flag_type f = std::regex_constants::ECMAScript );
basic_regex( const CharT* s, std::size_t count,
flag_type f = std::regex_constants::ECMAScript );
(3)
(since C++11)
flag_type f = std::regex_constants::ECMAScript );
basic_regex( const basic_regex& other );
(4)
(since C++11)
basic_regex( basic_regex&& other ) noexcept;
(5)
(since C++11)
template< class ST, class SA >
(6)
(since C++11)
explicit basic_regex( const std::basic_string <CharT,ST,SA>& str,
template< class ForwardIt >
(7)
(since C++11)
basic_regex( ForwardIt first, ForwardIt last,
basic_regex( std::initializer_list <CharT> init,
flag_type f = std::regex_constants::ECMAScript );
(8)
(since C++11)
flag_type f = std::regex_constants::ECMAScript );
Constructs a new regular expression from a sequence of characters interpreted according to the flags f.
1) Default constructor. Constructs an empty regular expression which will match nothing.
2) Constructs a regex from a null-terminated string s.
3) Constructs a regex from a sequence of count characters, pointed to by s.
4) Copy constructor. Constructs a regex by copying other.
5) Move constructor. Constructs a regex with the contents of other using move semantics.
6) Constructs a regex from a string str.
7) Range constructor. Constructs the string with the contents of the range
[first, last).8) Initializer list constructor. Constructs the string with the contents of the initializer list init.
[edit] Parameters
s
-
pointer to a null-terminated string
count
-
length of a character sequence used to initialize the regex
first, last
-
range of a character sequence used to initialize the regex
str
-
a basic_string used as a source used to initialize the regex
other
-
another regex to use as source to initialize the regex
init
-
initializer list used to initialize the regex
f
-
flags used to guide the interpretation of the character sequence as a regular expression
Type requirements
-
ForwardIt must meet the requirements of LegacyForwardIterator.
[edit] Exceptions
1) May throw implementation-defined exceptions.
2,3) std::regex_error if the supplied regular expression is not valid.
4) May throw implementation-defined exceptions.
6-8) std::regex_error if the supplied regular expression is not valid.
[edit] Example
Run this code
#include <iomanip> #include <iostream> #include <regex> #include <string> void match_and_print(const std::string & text, const std::regex & pattern) { std::sregex_iterator it(text.begin(), text.end(), pattern), it_end; int count = 0; for (; it != it_end; ++it) { const std::smatch & match = *it; std::cout << ++count << ". " << std::quoted (match.str()) << '\n'; } std::cout << (count ? "\n" : "no match found\n\n"); } int main() { const std::string text = "Hello, World! 12345"; // Matches one or more digits std::string pattern_text = "\\d+"; std::cout << "digits (" << pattern_text << "):\n"; auto pattern = std::regex (pattern_text); match_and_print(text, pattern); // Matches one or more characters split by space pattern_text = "[^\\s]+"; std::cout << "words (" << pattern_text << "):\n"; pattern = std::regex (pattern_text); match_and_print(text, pattern); // Matches one or more characters split by space pattern_text = "[a-zA-Z]+"; std::cout << "words without symbols and digits (" << pattern_text << "):\n"; pattern = std::regex (pattern_text); match_and_print(text, pattern); // Matches one non digits, non alphabet pattern_text = "[^0-9A-Za-z]"; std::cout << "symbol (" << pattern_text << "):\n"; pattern = std::regex (pattern_text); match_and_print(text, pattern); // Matches one or more lowercase pattern_text = "[a-z]+"; std::cout << "lowercase (" << pattern_text << "):\n"; pattern = std::regex (pattern_text); match_and_print(text, pattern); // Matches one or more lowercase with std::regex::icase flag pattern_text = "[a-z]+"; std::cout << "lowercase with ignore case flag (" << pattern_text << "):\n"; pattern = std::regex (pattern_text, std::regex::icase); match_and_print(text, pattern); // Matches basic POSIX regular expression pattern_text = "[[:digit:]]+"; std::cout << "basic POSIX regex (" << pattern_text << "):\n"; pattern = std::regex (pattern_text, std::regex::basic); match_and_print(text, pattern); // Matches extended POSIX regular expression pattern_text = "[[:digit:]]+"; std::cout << "extended POSIX regex (" << pattern_text << "):\n"; pattern = std::regex (pattern_text, std::regex::extended); match_and_print(text, pattern); }
Output:
digits (\d+): 1. "12345" words ([^\s]+): 1. "Hello," 2. "World!" 3. "12345" words without symbols and digits ([a-zA-Z]+): 1. "Hello" 2. "World" symbol ([^0-9A-Za-z]): 1. "," 2. " " 3. "!" 4. " " lowercase ([a-z]+): 1. "ello" 2. "orld" lowercase with ignore case flag ([a-z]+): 1. "Hello" 2. "World" basic POSIX regex ([[:digit:]]+): no match found extended POSIX regex ([[:digit:]]+): 1. "12345"