Item 31. Name Lookup and the Interface Principle—Part 1

Difficulty: 9½

When you call a function, which function do you call? The answer is determined by name lookup, but you're almost certain to find some of the details surprising.

In the following code, which functions are called? Why? Analyze the implications.

namespace A 
{
  struct X;
  struct Y;
  void f( int );
  void g( X );
}

namespace B
{
  void f( int i )
  {
    f( i );   // which f()?
  }
  void g( A::X x )
  {
    g( x );   // which g()?
  }
  void h( A::Y y )
  {
    h( y );   // which h()?
  }
}