Local classes (C++ only)

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A local class is declared within a function definition. Declarations in a local class can only use type names, enumerations, static variables from the enclosing scope, as well as external variables and functions.

For example:

int x;                         // global variable
void f()                       // function definition
{
   static int y;               // static variable y can be used by
                               // local class
   int x;                      // auto variable x cannot be used by
                               // local class
   extern int g();             // extern function g can be used by
                               // local class

   class local                 // local class
   {
      int g() { return x; }    // error, local variable x
                               // cannot be used by g
      int h() { return y; }    // valid,static variable y
      int k() { return ::x; }  // valid, global x
      int l() { return g(); }  // valid, extern function g
   };
}

int main()
{
   local* z;                   // error: the class local is not visible
   // ...
}

Member functions of a local class have to be defined within their class definition, if they are defined at all. As a result, member functions of a local class are inline functions. Like all member functions, those defined within the scope of a local class do not need the keyword inline.

A local class cannot have static data members. In the following example, an attempt to define a static member of a local class causes an error:

void f()
{
   class local
   {
      int f();               // error, local class has noninline
                             // member function
      int g() {return 0;}    // valid, inline member function
      static int a;          // error, static is not allowed for
                             // local class
      int b;                 // valid, nonstatic variable
   };
}
//      . . .

An enclosing function has no special access to members of the local class.

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