title: How do you call the structure which only contains a single operator (such as below)?
body: <p>I have seen this question in a C++ test and I have no idea what the solution should be.
  So in the code below, what is absValue?</p>
  
  <pre><code>#include &lt;iostream&gt; 
  
  struct absValue  
  {
         float operator()(float f) {
                   return f &gt; 0 ? f : -f;
    }  
  }; 
  
   int main( )   
  {
     using namespace std;
  
    float f = -123.45;  absValue aObj;
    float abs_f = aObj(f);
    cout &lt;&lt; "f = " &lt;&lt; f &lt;&lt; " abs_f = " &lt;&lt; abs_f &lt;&lt; endl;
    return 0;   
  } 
  </code></pre>