essential c++ 读书笔记1

妖狐艹你老母 2021-12-21 07:34 258阅读 0赞

ESSENTIAL C++

chapter  2

1,final implement of fib\_elem()

bool fibon_elem(int pos, int &elem){
      if(pos<=0||pos >=1024)
    //.........................
      elem=1;
      int n1=1,n2=1;
      for(int ix=3;ix<=pos;ix++)
      {
          elem=n1+n2;
          n2=n1;
          n1=elem;
      }
      return true;
    }

2, passing by value:(make a copy)    OR     passing by reference:(passing the address)

example :    swap(int a, int b)  OR   swap(int &a, int &b)

3,passing a pointer   OR   passing a reference parameter

passing a pointer:   before we dereference a pointer, we must always make sure it is NOT 0;

4, dynamic memory management

int *p;
    p=new int(100);  // set an initial value

delete p;

int *pia=new int[24];  // allocate an array of heap elements ; means int[24] pia;

delete[] pia;

5,  reference to an object

int ival=12;

int &rval=ival;

reference can not be re-assigned to other object

6,providing a default parameter value

void bubble_sort(vector<int> &vec., ofstream *ofil=0){} 
    //set pointer ofil to 0

unlike pointer, reference can not be set to 0

void display (const vector<int> &vec, ostream &os=cout){}

2 RULES about providing default parameter:

1, default values are resolved beginning with right most parameter ,if a parameter is provided a default value,all the parameter to its right must have a default

2, the default value can be specified only once

we can specify the default value in header files

8, local static object

const vector<int >*    fibon_seq(int size)
    {
    static vector<int> elems; //elems is local static object, elems is no longer
                                            //destroyed or re-created each invocations of fibon
    elems.push_back(1);
    return &elems;
    }

9, Inline function

inline bool fub(){}

10, overloaded function :(function must be unique)

11, template function

template<typename elemType>

vector<elemType> a;

12; Pointer to function

bool seq_elem(int pos, int &elem, const vector<int>*   (*seq_ptr)(int))   //to recognize seq_ptr as a pointer
    {
         const vector<int> *p=seq_ptr(pos);    //invoke the function

elem=(*p)[1];   
    }
    
    //you can also you a array to store function pointer
    const vector<int>* fib(int size);
    const vector<int>* (*seq_array[])(int)={fib, .......};
    seq_ptr=seq_array[1];

13, header file

if the header file is in the same directory as the program text file, we use " "

else we use <>

//header file called num.h
    //place in it some declaration 
    const vector<int>* fib(int size);
    //  elem=(*fib)[1]
    extern const vector<int>* (*seq[2])(int); // extern  turn the definition to   
                                                                      //declaration

转载于:https://www.cnblogs.com/ggppwx/archive/2010/05/22/1741620.html