std::regex_constants::error_type
From cppreference.com
Defined in header <regex> | ||
using error_type =/* implementation-defined */; | (1) | (since C++11) |
constexpr error_type error_collate = /* unspecified */; constexpr error_type error_ctype = /* unspecified */; | (2) | (since C++11) (inline since C++17) |
1) The
error_type is a type that describes errors that may occur during regular expression parsing.Contents |
[edit]Constants
| Name | Explanation |
error_collate | the expression contains an invalid collating element name |
error_ctype | the expression contains an invalid character class name |
error_escape | the expression contains an invalid escaped character or a trailing escape |
error_backref | the expression contains an invalid back reference |
error_brack | the expression contains mismatched square brackets ('[' and ']') |
error_paren | the expression contains mismatched parentheses ('(' and ')') |
error_brace | the expression contains mismatched curly braces ('{' and '}') |
error_badbrace | the expression contains an invalid range in a {} expression |
error_range | the expression contains an invalid character range (e.g. [b-a]) |
error_space | there was not enough memory to convert the expression into a finite state machine |
error_badrepeat | '*', '?', '+' or '{' was not preceded by a valid regular expression |
error_complexity | the complexity of an attempted match exceeded a predefined level |
error_stack | there was not enough memory to perform a match |
[edit]Example
Implements regular expressions checker:
Run this code
#include <cstddef>#include <iomanip>#include <iostream>#include <regex>#include <sstream>#include <string> void regular_expression_checker(conststd::string& text, conststd::string& regex, const std::regex::flag_type flags){std::cout<<"Text: "<<std::quoted(text)<<'\n'<<"Regex: "<<std::quoted(regex)<<'\n'; try{conststd::regex re{regex, flags};constbool matched =std::regex_match(text, re); std::stringstream out; out <<(matched ?"MATCH!\n":"DOES NOT MATCH!\n"); std::smatch m;if(std::regex_search(text, m, re);!m.empty()){ out <<"prefix = ["<< m.prefix().str().data()<<"]\n"; for(std::size_t i{}; i != m.size();++i) out <<" m["<< i <<"] = ["<< m[i].str().data()<<"]\n"; out <<"suffix = ["<< m.suffix().str().data()<<"]\n";}std::cout<< out.str()<<'\n';}catch(std::regex_error& e){std::cout<<"Error: "<< e.what()<<".\n\n";}} int main(){constexpr std::regex::flag_type your_flags = std::regex::flag_type{0}// Choose one of the supported grammars:| std::regex::ECMAScript// | std::regex::basic// | std::regex::extended// | std::regex::awk// | std::regex::grep// | std::regex::egrep// Choose any of the next options:// | std::regex::icase// | std::regex::nosubs// | std::regex::optimize// | std::regex::collate// | std::regex::multiline; conststd::string your_text ="Hello regular expressions.";conststd::string your_regex = R"(([a-zA-Z]+) ([a-z]+) ([a-z]+)\.)"; regular_expression_checker(your_text, your_regex, your_flags); regular_expression_checker("Invalid!", R"(((.)(.))", your_flags); regular_expression_checker("Invalid!", R"([.)", your_flags); regular_expression_checker("Invalid!", R"([.]{})", your_flags); regular_expression_checker("Invalid!", R"([1-0])", your_flags);}
Possible output:
Text: "Hello regular expressions." Regex: "([a-zA-Z]+) ([a-z]+) ([a-z]+)\\." MATCH! prefix = [] m[0] = [Hello regular expressions.] m[1] = [Hello] m[2] = [regular] m[3] = [expressions] suffix = [] Text: "Invalid!" Regex: "((.)(.)" Error: Mismatched '(' and ')' in regular expression. Text: "Invalid!" Regex: "[." Error: Unexpected character within '[...]' in regular expression. Text: "Invalid!" Regex: "[.]{}" Error: Invalid range in '{}' in regular expression. Text: "Invalid!" Regex: "[1-0]" Error: Invalid range in bracket expression..[edit]Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 2053 | C++11 | the constants were declared static | removed the static specifier |
[edit]See also
(C++11) | reports errors generated by the regular expressions library (class) |
