title: Can I re-define a function or check if it exists?
body: <p>I have a question about (re-)defining functions. My goal is to have a script where I can choose to define a function or not.
  Like this:</p>
  
  <pre><code>void func(){}
  
  int main(){
     if (func)func();
  }
  </code></pre>
  
  <p>AND without the function, just:</p>
  
  <pre><code>int main(){
     if (func)func();
  }
  </code></pre>
  
  <p>Anybody an idea?</p>