(1) (since C++11)
regex_iterator( BidirIt a, BidirIt b,

                const regex_type& re,
                std::regex_constants::match_flag_type m =

                    std::regex_constants::match_default );
(2) (since C++11)
regex_iterator( const regex_iterator& );
(3) (since C++11)
regex_iterator( BidirIt, BidirIt,

                const regex_type&&,
                std::regex_constants::match_flag_type =

                    std::regex_constants::match_default ) = delete;
(4) (since C++11)

Constructs a new regex_iterator:

1) Default constructor. Constructs an end-of-sequence iterator.
2) Constructs a regex_iterator from the sequence of characters [a, b), the regular expression re, and a flag m that governs matching behavior. This constructor performs an initial call to std::regex_search with this data. If the result of this initial call is false, *this is set to an end-of-sequence iterator.
3) Copies a regex_iterator.
4) The overload (2) is not allowed to be called with a temporary regex, since the returned iterator would be immediately invalidated.

[edit] Parameters

a - LegacyBidirectionalIterator to the beginning of the target character sequence
b - LegacyBidirectionalIterator to the end of the target character sequence
re - regular expression used to search the target character sequence
m - flags that govern the behavior of re

[edit] Example

#include <iostream>
#include <regex>
#include <string_view>
int main()
    constexpr std::string_view str{"#ONE:*p=&Mass; #Two:MOV %rd,42"};
    const std::regex re("[a-w]");
    // create regex_iterator, overload (2)
    auto it = std::regex_iterator<std::string_view::iterator>{
        str.cbegin(), str.cend(),
        re // re is lvalue; if an immediate expression was used
           // instead, e.g. std::regex{"[a-z]"}, this would
           // produce an error - overload (4) is deleted
    for (decltype(it) last /* overload (1) */; it != last; ++it)
        std::cout << (*it).str();



[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 2332 C++11 a regex_iterator constructed from a temporary
basic_regex became invalid immediately
such construction is disallowed via a deleted overload