The following code example is taken from the book
The C++ Standard Library - A Tutorial and Reference, 2nd Edition
by Nicolai M. Josuttis, Addison Wesley Longman, 2012
Copyright © 2012 by Pearson Education, Inc. and Nicolai M. Josuttis
#include <regex>
#include <string>
template <typename T>
std::string regexCode (T code)
{
switch (code) {
case std::regex_constants::error_collate:
return "error_collate: "
"regex has invalid collating element name";
case std::regex_constants::error_ctype:
return "error_ctype: "
"regex has invalid character class name";
case std::regex_constants::error_escape:
return "error_escape: "
"regex has invalid escaped char. or trailing escape";
case std::regex_constants::error_backref:
return "error_backref: "
"regex has invalid back reference";
case std::regex_constants::error_brack:
return "error_brack: "
"regex has mismatched '[' and ']'";
case std::regex_constants::error_paren:
return "error_paren: "
"regex has mismatched '(' and ')'";
case std::regex_constants::error_brace:
return "error_brace: "
"regex has mismatched '{' and '}'";
case std::regex_constants::error_badbrace:
return "error_badbrace: "
"regex has invalid range in {} expression";
case std::regex_constants::error_range:
return "error_range: "
"regex has invalid character range, such as '[b-a]'";
case std::regex_constants::error_space:
return "error_space: "
"insufficient memory to convert regex into finite state";
case std::regex_constants::error_badrepeat:
return "error_badrepeat: "
"one of *?+{ not preceded by valid regex";
case std::regex_constants::error_complexity:
return "error_complexity: "
"complexity of match against regex over pre-set level";
case std::regex_constants::error_stack:
return "error_stack: "
"insufficient memory to determine regex match";
}
return "unknown/non-standard regex error code";
}