Scott Meyers posted [content and status][1] of his next book EC++11.
He wrote that one item in the book could be *&quot;Avoid `std::enable_if` in function signatures&quot;*.

`std::enable_if` can be used as a function argument, as a return type or as a class template or function template parameter to conditionally remove functions or classes from overload resolution.

In [this question][2] all three solution are shown.

As function parameter:


    template&lt;typename T&gt;
    struct Check1
    {
       template&lt;typename U = T&gt;
       U read(typename std::enable_if&lt;
              std::is_same&lt;U, int&gt;::value &gt;::type* = 0) { return 42; }

       template&lt;typename U = T&gt;
       U read(typename std::enable_if&lt;
              std::is_same&lt;U, double&gt;::value &gt;::type* = 0) { return 3.14; }   
    };


As template parameter:

    template&lt;typename T&gt;
    struct Check2
    {
       template&lt;typename U = T, typename std::enable_if&lt;
                std::is_same&lt;U, int&gt;::value, int&gt;::type = 0&gt;
       U read() { return 42; }

       template&lt;typename U = T, typename std::enable_if&lt;
                std::is_same&lt;U, double&gt;::value, int&gt;::type = 0&gt;
       U read() { return 3.14; }   
    };


As return type:

    template&lt;typename T&gt;
    struct Check3
    {
       template&lt;typename U = T&gt;
       typename std::enable_if&lt;std::is_same&lt;U, int&gt;::value, U&gt;::type read() {
          return 42;
       }

       template&lt;typename U = T&gt;
       typename std::enable_if&lt;std::is_same&lt;U, double&gt;::value, U&gt;::type read() {
          return 3.14;
       }   
    };


  [1]: http://scottmeyers.blogspot.de/2013/01/effective-c11-content-and-status.html
  [2]: https://stackoverflow.com/questions/11055923/stdenable-if-parameter-vs-template-parameter

 * Which solution should be preferred and why should I avoid others? 
 * In which cases *&quot;Avoid `std::enable_if` in function signatures&quot;* concerns usage as return type (which is not part of normal function signature but of template specializations)?
 * Are there any differences for member and non-member function templates?

All Enable If Solutions on Gang of Coders

Total of 1 Enable If Solutions

Why should I avoid std::enable_if in function signatures