title: How to build parse tree?
body: <p>Have found C++ BNF and there next lines</p>
  
  <pre><code>selection-statement:
      if ( condition ) statement
      if ( condition ) statement else statement
  </code></pre>
  
  <p>Now trying to write parser. Need to build parse tree. On input i have BNF and source file. But i'm stucked in how i can point my parser what if <em>condition</em> evaluated to true, then it need to execute first statement otherwise else block? Thanks.</p>