title: Why is it inserting a ? (question mark) right before Map entry?
body: <p>Yaml-cpp seems to be inserting a question mark right before my map entry. This is the outcome:</p>
  
  <pre><code>baryons:
    nucleons:
      - proton:
          quarkContent: [u, u, d]
          charge: 1
      - antiproton:
          quarkContent: [au, au, ad]
          charge: -1
      - neutron:
          quarkContent: [d, d, u]
          charge: 0
      - antineutron:
          quarkContent: [ad, ad, au]
          charge: 0
  ? hyperons:
      - lambda:
          quarkContent: [u, d, s]
          charge: 0
      - antilambda:
          quarkContent: [au, ad, as]
          charge: 0
  </code></pre>
  
  <p>As you can see, beginning with hyperons, there is a question mark. I tried adding more entries to see what happens. It seems to alternate between <code>?</code> and <code>:</code>. This is quite strange.</p>
  
  <p>I tried removing all the contents of the nucleons key and the hyperons key, and I still get this</p>
  
  <pre><code>baryons:
    nucleons:
      - Hello
  ? hyperons:
      - Hello
  </code></pre>
  
  <p>Mmm. quite odd indeed. Here is my code. Forgive the messiness</p>
  
  <pre><code>#include "yaml-cpp/yaml.h"
  #include &lt;string&gt;
  #include &lt;sstream&gt;
  #include &lt;iostream&gt;
  #include &lt;fstream&gt;
  #include &lt;typeinfo&gt;
  using namespace YAML;
  
  void addParticle(Emitter * e, std::string name, std::string qc1, std::string qc2, std::string qc3, int charge){
      *e &lt;&lt; BeginMap &lt;&lt; Key &lt;&lt; name;
      *e &lt;&lt; Value;
          *e &lt;&lt; BeginMap;
          *e &lt;&lt; Key &lt;&lt; "quarkContent" &lt;&lt; Value &lt;&lt; Flow &lt;&lt; BeginSeq &lt;&lt; qc1 &lt;&lt; qc2 &lt;&lt; qc3 &lt;&lt; EndSeq;
          *e &lt;&lt; Key &lt;&lt; "charge" &lt;&lt; Value &lt;&lt; charge;
          *e &lt;&lt; EndMap;
      *e &lt;&lt; EndMap;
  
      *e &lt;&lt; BeginMap &lt;&lt; Key &lt;&lt; "anti" + name;
      *e &lt;&lt; Value;
          *e &lt;&lt; BeginMap;
          *e &lt;&lt; Key &lt;&lt; "quarkContent" &lt;&lt; Value &lt;&lt; Flow &lt;&lt; BeginSeq &lt;&lt; "a" + qc1 &lt;&lt; "a" + qc2 &lt;&lt; "a" + qc3 &lt;&lt; EndSeq;
          *e &lt;&lt; Key &lt;&lt; "charge" &lt;&lt; Value &lt;&lt; charge * -1;
          *e &lt;&lt; EndMap;
      *e &lt;&lt; EndMap;
  };
  
  int main(){
      Emitter e;
  
      e &lt;&lt; BeginMap;
      e &lt;&lt; Key &lt;&lt; "baryons";
      e &lt;&lt; Value;
  
          e &lt;&lt; BeginMap;
          e &lt;&lt; Key &lt;&lt; "nucleons";
          e &lt;&lt; Value;
              e &lt;&lt; BeginSeq;
              addParticle(&amp;e, "proton", "u", "u", "d", 1);
              addParticle(&amp;e, "neutron", "d", "d", "u", 0);
              e &lt;&lt; EndSeq;
          e &lt;&lt; EndMap;
  
          e &lt;&lt; BeginMap;
          e &lt;&lt; Key &lt;&lt; "hyperons";
          e &lt;&lt; Value;
              e &lt;&lt; BeginSeq;
              addParticle(&amp;e, "lambda", "u", "d", "s", 0);
              e &lt;&lt; EndSeq;
          e &lt;&lt; EndMap;
  
      e &lt;&lt; EndMap;
  
      std::ofstream particlesYAML;
      particlesYAML.open("particles.yml");
      particlesYAML.write(e.c_str(), strlen(e.c_str()));
      particlesYAML.close();
      return 0;
  };
  </code></pre>
  
  <p>On a side note, I'm indenting to reduce clutter. So forgive that too.</p>
  
  <p>Also, is my YAML structure good? Or should I revise to something different? Thanks.</p>