title: How to calculate Euler constant or Euler powered in C++?
body: <p>I am trying to find the more 'natural' way to use the number <em>e</em> in C/C++. I am focused on calculating the function <em>e</em>^n.</p>
  
  <p>I think that 'cmath', by default, does not provide support for both (function and constant). However, it can be enabled to include constants defined by the compiler, in this case, <code>M_E</code>. This can be done by including the statement <code>#define _USE_MATH_DEFINES</code>.</p>
  
  <p>On the other hand, <em>e</em> can be defined as a constant:</p>
  
  <pre><code>#define E 2.71828182845904523536;
  </code></pre>
  
  <p>or</p>
  
  <pre><code>const double EULER = 2.71828182845904523536;
  </code></pre>
  
  <p>Said this. Which one is the most 'standard' way to approach to this mathematical constant? Is it any other library?</p>