title: how to use C++11 integral_constant::value_type()
body: <p>I am learning to use C++ 11 type_traits, in integral_constant, there is a function value_type();</p>
  
  <p>I tried this but got error:</p>
  
  <pre><code>typedef std::integral_constant&lt;int, 1&gt; one_t;
  one_t one_o;
  one_o.value_type();
  </code></pre>
  
  <blockquote>
    <p>../src/main.cc:13:9: error: cannot refer to type member 'value_type'
    in 'one_t' (aka 'integral_constant') with '.'<br>
    one_o.value_type();</p>
  </blockquote>