title: Checking if a function with a given signature exists in c++
body: <p>So I was looking for ways to check whether a function with a particular argument exists. I have a templated method which relies on an external function (external from the class) to do the job:</p>
  
  <pre><code>  template &lt;class Moo&gt;
    void exportDataTo(Moo&amp; ret){
       extended_solid_loader(ret, *this);
    }
  </code></pre>
  
  <p>At multiple points in the project I have macros which define extended_solid_loader for different types, but now I want to be able to use a default function if extended_solid_loader hasn't been defined for that particular class type.</p>
  
  <p>I came across this:
  <a href="https://stackoverflow.com/questions/257288/is-it-possible-to-write-a-c-template-to-check-for-a-functions-existence">Is it possible to write a template to check for a function&#39;s existence?</a>
  but it seems a little different, in that I'm not checking for a method, but rather a definition of a function with a particular argument type.</p>
  
  <p>Is this possible right now?</p>