title: How to create a uni-parameter template from a dual-parameter template to use as a base class template template parameter
body: <p>Below is an example of what I am trying to do. I am just using it to illustrate the problem.</p>
  
  <pre><code>#include &lt;iostream&gt;
  using namespace std;
  
  template &lt;int STEP, bool SIDE&gt; class Stepper {
      int step( int x ) {
          return SIDE ? x + STEP : x - STEP;
      }
  };
  
  template &lt;template &lt;bool&gt; typename STEPPER&gt; class DualStepper {
      STEPPER&lt;true&gt; upStepper;
      STEPPER&lt;false&gt; downStepper;
  
      pair&lt;int , int&gt; step( int x ) {
          return pair&lt;int , int&gt;( upStepper.step( x ), downStepper.step( x ) );
      }
  };
  
  
  template &lt;int STEP&gt; class FixedDualStepper : public DualStepper&lt;template &lt;bool SIDE&gt; using FT = Stepper&lt;STEP, SIDE&gt;&gt; {
  
  };
  
  
  int main() {
  
      FixedDualStepper&lt;5&gt; stepper;
      pair&lt;int, int&gt; x = stepper.step( 10 );
      cout &lt;&lt; x.first &lt;&lt; '\t' &lt;&lt; x.second &lt;&lt; endl;
  
      return 0;
  }
  </code></pre>
  
  <p>For this I get the error:</p>
  
  <pre><code>/Work/Learn/04PartialTemplate/main.cpp:23:115: error: template argument 1 is invalid
  template &lt;int STEP&gt; class FixedDualStepper : public DualStepper&lt;template &lt;bool SIDE&gt; using FT = Stepper&lt;STEP, SIDE&gt;&gt; {
                                                                                                                 ^
  /Work/Learn/04PartialTemplate/main.cpp: In function ‘int main()’:
  /Work/Learn/04PartialTemplate/main.cpp:31:29: error: ‘class FixedDualStepper&lt;5&gt;’ has no member named ‘step’
     pair&lt;int, int&gt; x = stepper.step( 10 );
  </code></pre>
  
  <p>Is there a syntax I could use in </p>
  
  <pre><code>... : public DualStepper&lt; ??? &gt;
  </code></pre>
  
  <p>to get the desired effect. I.e. set the first parameter of <code>Stepper</code> to <code>STEP</code> and get a single parameter class template to use as a template template parameter for <code>DualStepper</code>?</p>