basic_regex(); | (1) | (since C++11) |
explicit basic_regex( const CharT* s, flag_type f = std::regex_constants::ECMAScript ); | (2) | (since C++11) |
basic_regex( const CharT* s, std::size_t count, flag_type f = std::regex_constants::ECMAScript ); | (3) | (since C++11) |
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 > explicit basic_regex( const std::basic_string<CharT,ST,SA>& str, flag_type f = std::regex_constants::ECMAScript ); | (6) | (since C++11) |
template< class ForwardIt > basic_regex( ForwardIt first, ForwardIt last, flag_type f = std::regex_constants::ECMAScript ); | (7) | (since C++11) |
basic_regex( std::initializer_list<CharT> init, flag_type f = std::regex_constants::ECMAScript ); | (8) | (since C++11) |
Constructs a new regular expression from a sequence of characters interpreted according to the flags f
.
s
.count
characters, pointed to by s
.other
.other
using move semantics.str
.[
first
,
last
)
.init
.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. |
std::regex_error
if the supplied regular expression is not valid.std::regex_error
if the supplied regular expression is not valid.#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"
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