Namespaces

namespaces.cpp

/* We have three ways of importing the literals in something designed
   like the standard library: */
void my_function() {
  /* Means "now all of foo is the most important thing in this
     function" -> implies shift from what was most important outside
     this function */
  using namespace foo;
  // OR
  /* Means "now the user-defined literals from foo are important" ->
     implies everything else is like outer scope
  */
  using namespace foo::literals;
  // OR
  /* Means "now the _abc user-defined literal from foo is important" */
  using namespace foo::literals::abc_literals;

  /* See how these all mean slightly different things, even though
     they all let you type 123_abc and get the one from foo?  My
     contention is that these slight shades of meaning, when used
     correctly, aid tremendously in reasoning about software (my
     experience with Perl, C++, and Haskell has taught me this).  I
     should probably write this up, because I think we agree on the
     what I consider the fundamental idea (we want our software to be
     readable), but the path from there to here may not be immediately
     apparent. */
}