C++Primer读书笔记(2)-引用和类型

2.5

A reference serves as a alternative name for an object. In real-world programs,reference are primarily used as formal parameters to functions.

int ival=1024;

int &refVal=ival;  //ok: refVal refers to  ival

int &refVal2;       //error: a reference must be initialized

int &refVal3=10; //error:initializer must be an object 

Because a refernce is just another name for the object to which it is bound,all operations on a reference are actually operations on the underlying object

to which the reference is bound;

2.6

A typedef lets us define a synonym for a type

tydedef  double wages;       //wages is a synonym for double

typedef int exam_score;    //exam_score is a synonym for int

typedef wages salary;       //indirect synonym for double

wages hourly,weekly;      //double hourly,weekly;

exam_score test_result;  //int test_result;

Typedefs are commonly used for one of three purposes:

1.To  hide the implementation of a given type and emphasize instead the purpose  for which the type is used

2.To streamline complex type definitions,making them easier to understand

3.To allow a single type to be used for more than one purpose while making the purpose clear each time the type is used