How does parsing to `vector<string>` work?

[akrzemi1]

In the following piece of code the goal is to parse a sequence of identifiers -- like "id1 id_ idx" -- into a vector<string>:

void parse_sequence_of_identifiers()
{
  namespace bp = boost::parser;

  auto id = bp::lexeme[+(bp::ascii::alnum | bp::char_('_'))]; 
  auto ids = +id;

  std::string str;
  std::vector<std::string> vec;

  bp::parse("id1", id, bp::ascii::space, str);      // (1)
  bp::parse("id1 id2", ids, bp::ascii::space, vec); // (2)
  bp::parse("i1 i2", ids, bp::ascii::space, str);   // (3)
}

(1) works fine. (2) fails to compile. (3) compiles and reports success, but the result is an empty string. This goes surely against the intuitive expectations.

[akrzemi1]

I should have mentioned that (2) above works as expected in Boost.Spirit: https://godbolt.org/z/KsPxnnenz

[tzlaine]

Thanks for catching this. Clearly I did not test enough cases. (1) and (2) should work as of the patches that I just pushed to develop (if everything is fine, they'll land on master soonish, with a doc update). (3) is a bone-headed mistake on my part that breaks probably everything if supported. I've left (3) ill-formed for now.

[akrzemi1]

Thanks. This Issue is actually about (2).

Regarding (3), I would never expect it to work. I was actually surprised that it compiled. If it now fails to compile, then I am happy.