Null is expected to output empty string, instead of tilde, so that it is loadable to Null.

What steps will reproduce the problem?
  YAML::Node node = YAML::Load("---\n...");
  std::ostream << node << std::endl;

What is the expected output? What do you see instead?
an empty string is expected.
currently shows a tilde(~),
which is loaded to a string of "~", instead of Null.

What version of the product are you using? On what operating system?
The latest (on 2013/12/12) revision at the hg repository,
Mac OS X Mavericks.

Please provide any additional information below.
http://stackoverflow.com/questions/20544174/how-to-specify-the-output-format-for
-null-node-in-yaml-cpp

Original issue reported on code.google.com by inouetak...@gmail.com on 14 Dec 2013 at 1:06

graehl / yaml-cpp-old

Null is expected to output empty string, instead of tilde, so that it is loadable to Null. #230