char ch;
string s;
int count = 1;
const double pi = 3.1415926535897932385;
extern int error_number;

const char* name = "Njal";
const char* season[] = { "spring","summer","fall","winter" };

struct Date { int d,m,y; };
int day(Date* p) { return p->d; }
double sqrt(double);
template<class T> T abs(T a) { return a<0 ? -a : a; }

typedef complex<short> Point;
struct User;
enum Beer { Carlsberg,Tuborg,Thor };
namespace NS { int a; }

As can be seen from these examples,a declaration can do more than simply
associate a type with a name. Most of these declarations are also definitions;
that is,they also define an entity for the name to which they refer. For ch,
that entity is the appropriate amount of memory to be used as a variable – that
memory will be allocated. For day it is the specified function. For the
constant pi,it is the value 3.1415926535897932385. For Date,that entity is
a new type. For Point it is the type complex so that Point becomes a
synonym for complex. Of the declarations above,only these are not also
definitions:

double sqrt(double);
extern int error_number;
struct User;
typedef complex<short> Point <-- WTF;

大胆的句子是不是与下面给出的列表冲突了？ typedef只是一个声明还是一个定义？这是书中的错误吗？