Boost split string by Blank Line

Question

Is there a way to use boost::split to split a string when a blank line is encountered?

Here is a snippet of what I mean.

std::stringstream source;
source.str(input_string);
std::string line;
std::getline(source, line, '\0');
std::vector<std::string> token;
boost:split(token,line, boost::is_any_of("what goes here for blank line");

Answer 1

You can split by double \n\n unless you meant blank line as "a line that may contain other whitespace".

Live On Coliru

#include <boost/regex.hpp>
#include <boost/algorithm/string_regex.hpp>
#include <boost/algorithm/string/classification.hpp>
#include <sstream>
#include <iostream>
#include <iomanip>

int main() {
    std::stringstream source;
    source.str(R"(line one

that was an empty line, now some whitespace:
      
bye)");

    std::string line(std::istreambuf_iterator<char>(source), {});
    std::vector<std::string> tokens;

    auto re = boost::regex("\n\n");
    boost::split_regex(tokens, line, re);

    for (auto token : tokens) {
        std::cout << std::quoted(token) << "\n";
    }
}

Prints

"line one"
"that was an empty line, now some whitespace:
      
bye"

Allow whitespace on "empty" lines

Just express it in a regular expression:

auto re = boost::regex(R"(\n\s*\n)");

Now the output is: Live On Coliru

"line one"
"that was an empty line, now some whitespace:"
"bye"