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
    
      &vec., ofstream *ofil=0){} //set pointer ofil to 0
    

unlike pointer, reference can not be set to 0

7,

void display (const vector
    
      &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
    
     *    fibon_seq(int size){static vector
     
       elems; //elems is local static object, elems is no longer                                        //destroyed or re-created each invocations of fibonelems.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
    
     *   (*seq_ptr)(int))   //to recognize seq_ptr as a pointer{     const vector
     
       *p=seq_ptr(pos);    //invoke the function
     
    

elem=(*p)[1];   }//you can also you a array to store function pointerconst vector
    
     * fib(int size);const vector
     
      * (*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
    
     * fib(int size);//  elem=(*fib)[1]extern const vector
     
      * (*seq[2])(int); // extern  turn the definition to                                                                     //declaration