title: inline vs. constexpr?
body: <p>With the new C++11 standard, when should I use the <code>inline</code> keyword over the <code>constexpr</code> keyword?  Does the <code>constexpr</code> keyword offer any additional optimization over <code>inline</code>, or does it merely assert that things must be computed at compile-time?</p>
  
  <p>Why does <code>constexpr</code> work on the GCC in some cases where the call is not constant, such as calling <code>foo(x)</code> on a non-<code>constexpr</code> variable?  Is this a bug in the GCC or is it actually part of the standard?</p>