C + + functions and pointers

Recently in the C + + primer Plus, the sense function and pointer this chapter more difficult, write notes, strengthen understanding.

From C + + Primer Plus:chapter 7 function:c++ Programming Modules

1. How do I declare a function pointer?

Similar to function prototypes: You need to declare the pointer to the function's return value and argument list

Double pam (int); The argument is of type int, a function that returns a double type of double (*PF);(int)  //points to an int type, and a pointer pf = Pam with a double type returned value;   The function name represents the address of a double x = Pam (4); The function name is called double x = (*PF) (4); The pointer is called Double x = PF (4); C + + also allows pointer names to be used as function names

2. C + + 11 automatic type inference

Const DOUBLE * F1 (const double *, int); Const double * (*P1) (const double *, int); P1 poitns to f1 auto P2 = f1; C++11 automatic type DEDUCTION,P2 points to F1 as well

3. Use the pointer name as a function name

The preceding function is a double * type, cout the first part returns a double pointer, the second part returns the value pointed to by the double pointer cout<< (*P1) (av,3) << ":" <<* (*P1) (av,3) <<endl;//, like the cout above, simply calls the function using the function pointer name COUT<<P2 (av,3) << ":" <<*p2 (av,3) <<endl;

4. Array of function pointers

Const double * (*PA[3]) (const double *,int) = {F1,F2,F3}; Create an array of function pointers//call functions via pointers, get the returned pointer const double *PX = pa[0] (av,3); Call by pointer as if it were a function nameconst double *py = (*pa[0]) (av,3); The normal call//Get function returns the value that the pointer points to double x = *pa[0] (av,3);d ouble x = * (*pa[0]) (av,3);

5. Pointers to pointer arrays

The difference between pointer arrays and arrays of pointers

*PD[3]//an array of 3 pointers (*PD) [3]//a pointer to an array of three elements

Pointer to array

1 Auto PC = &pa; &PA is the address of the entire array, and the PA is the first element of the array

2

3 Const DOUBLE * (* (*PD) [3]) (const double *, int) = &pa; And the first equivalent of

4

5 **&pa = *pa = Pa[0]

Code:

Arfupt.cpp--an array of function pointers#include<iostream>//various notations,same signaturesconst double *f1 (const double ar[],int n); const double *F2 (const double [],int); const double *F3 (const double *,int); int main () {using    namespace Std;    Double Av[3] = {1112.3,1542.6,2227.9};    Pointer to a function const double * (*P1) (const double *,int) = F1; Auto P2 = f2;//c++ utomatic type deduction//pre-c++11 can use the following code instead//const double * (*P2) (    Const double *,int) = F2;    cout<< "Using pointers to functions:\n";    cout<< "Address value\n";    cout<< (*P1) (av,3) << ":" <<* (*P1) (av,3) <<endl;    COUT&LT;&LT;P2 (av,3) << ":" <<*p2 (av,3) <<endl; PA An array of pointers//auto doesn ' t work with list initialization const double * (*PA[3]) (const double *,int) =    {F1,F2,F3};    PB a pointer to first element of PA auto PB = pa; PRE-C++11 can use the following code instead/CONSt Double * (**PB) (const double *, int) = PA;    cout<< "\nusing An array of pointers to functions:\n";    cout<< "Address value\n";    for (int i = 0;i < 3; i++) Cout<<pa[i] (av,3) << ":" <<*pa[i] (av,3) <<endl;    cout<< "\nusing A pointer to a pointer to a function:\n";    cout<< "Address value\n";    for (int i = 0;i < 3; i++) Cout<<pb[i] (av,3) << ":" <<*pb[i] (av,3) <<endl;    What is a pointer to an array of function pointers cout<< "\nusing pointers to an array of pointers:\n";    cout<< "Address value\n";    Easy-to-declare pc auto PC = &pa;    PRE-C++11 can use the following code instead//CONST DOUBLE * (* (*PC) [3]) (const double *, int) = &pa;    cout<< (*PC) [0] (av,3) << ":" <<* (*PC) [0] (av,3) <<endl;    Hard-to-declare PD const DOUBLE * (* (*PD) [3]) (const double *,int) = &pa; Store return value in pdb const double *pdb = (*PD)[1]    (av,3);    cout<<pdb<< ":" <<*pdb<<endl; Alternative notation cout<< (* (PD) [2]) (av,3) << ":" <<* (* (*PD) [2]) (av,3) <<endl;} Const DOUBLE * F1 (const double * ar, int n) {return ar;} Const DOUBLE * F2 (const double ar[], int n) {return ar+1;} Const DOUBLE * F3 (const double ar[], int n) {return ar+2;}