answer.first=true;
answer.second=false;
answer.third=true;
...

answer.first=true;
answer.second.first=false;
answer.second.second=true;

struct inception {
    struct inception first;
    struct inception second;
};

struct A
  {
  A a;  // compile error -- "incomplete/unresolved type" or "infinite recursion" or somesuch
  };

struct A
  {
  A* a;  // fine
  };

struct pair
  {
  bool is_pair;       // Is our car an atom or a pair?
  union
    {
    const char* a;    // In this example, our atoms are simple strings
    pair*       p;
    }           car;  // Traditional name for the first element in a pair
  pair*         cdr;  // Traditional name for the second element in a pair
  };

pair* new_empty()
  {
  pair* e = new pair;
  e.is_pair = false;
  e.car.s   = NULL;
  e.cdr     = NULL;
  return e;
  }

pair* new_atom( const char* s )
  {
  pair* a = new pair;
  a.is_pair = false;
  a.car.s   = s;
  a.cdr     = NULL;
  return a;
  }

pair* new_atom( pair* p )
  {
  pair* a = new pair;
  a.is_pair = true;
  a.car.p   = p;
  a.cdr     = NULL;
  return a;
  }

pair* new_pair( const char* s, pair* p )
  {
  pair* a = new_atom( s );
  a.cdr = p;
  return a;
  }

pair* new_pair( pair* p1, pair* p2 )
  {
  pair* a = new_atom( p1 );
  a.cdr = p2;
  return a;
  }

// list <-- (one two three)
pair* list = new_pair( "one", new_pair( "two", new_pair( "three", new_empty() ) ) );

// list <-- (one two . three)
pair* list = new_pair( "one", new_pair( "two", new_atom( "three" ) ) );