OPTIONAL yaml_cpp
{
}

#include <cctk.h>

#ifdef HAVE_CAPABILITY_yaml_cpp
#include <yaml-cpp/yaml.h>
#endif

  }
#ifdef HAVE_CAPABILITY_yaml_cpp
  friend YAML::Emitter &operator<<(YAML::Emitter &yaml, const rational &x) {
    yaml << YAML::LocalTag("rational-1.0.0");
    yaml << YAML::Flow << YAML::BeginSeq << x.num << x.den << YAML::EndSeq;
    return yaml;

#endif