std::regex_replace only first occurence

Question

std::regex_replace (Added in C++ 11) replaces all the occurrences. How can I make it replace only the first occurrence?

Answer 1

If the flags parameter to std::regex_replace contains std::regex_constants::format_first_only , only the first match is replaced.

std::regex_replace("12 34",
                   std::regex(R"(\d+)"),
                   "num",
                    std::regex_constants::format_first_only);

stribizhev kindly provided a working example .

Answer 2

I found the solution myself. Posting for others if they face the same issue. Add:

std::tr1::regex_constants::format_first_only

to replace only the first occurrence as the fourth argument to regex_replace