title: How do you define a global function in C++?
body: <p>I would like a function that is not a member of a class and is accessible from any class.</p>
  
  <p>I assume I would have to <code>#include</code> the header file where the function is declared, but I don't know where to define such a global function.</p>
  
  <p>Are there good reasons against having such a function in the first place?</p>