"C + + Primer, 5e" function pointer

A simple example:

#include <iostream>using namespacestd;intSumintXinty) {    returnX +y;}intMain () {cout<< sum (1,2) <<Endl; int(*PF) (int,int);//not initializedPF =sum; cout<< PF (3,4) <<Endl; /*Output:3 7*/    return 0;}

In case of overloading, the compiler precisely matches the function by pointer type.

#include <iostream>using namespacestd;intSumintXinty) {    returnX +y;}intSumintXDoubley) {cout<<"sum2"<<Endl; returnX +y;}intMain () {cout<< sum (1,2) <<Endl; int(*PF) (int,int);//not initializedPF =sum; cout<< PF (3,4) <<Endl; /*Output:3 7*/    return 0;}

To use a function as an argument:

#include <iostream>using namespacestd;intSumintXinty) {    returnX +y;} typedef decltype (SUM) func;intUseInt2 (intXintY, func f) {    returnf (x, y);}intMain () {cout<< UseInt2 (3,4, sum) <<Endl; /*output = 7*/    return 0;}

The return type is not automatically converted to a pointer, we must display the return type as a pointer, but I think the return function is useless unless it is inside the function that can also be used to construct functions such as Python.

Practice

6.54

 #include <iostream> #include  <vector> using  namespace   STD;  int  sum (int  x, int   y) { return  x + y;}  int   main () { using  pf = int  (*) (int , int   <pf> Pfvec;  return  0  ;}  

6.55 & 6.56

#include <iostream>#include<vector>using namespacestd;intAddintXinty) {    returnX +y;}intSubtractintXinty) {    returnX-y;}intMultiplyintXinty) {    returnX *y;}intDivideintXinty) {    returnX/y;}intMain () {usingPF =int(*) (int,int); Vector<pf>Pfvec;    Pfvec.push_back (add);    Pfvec.push_back (subtract);    Pfvec.push_back (multiply);    Pfvec.push_back (divide);  for(pf F:pfvec) {cout<< F ( A,4) <<Endl; }    return 0;}

Output Result:

 - 8  - 3

"C + + Primer, 5e" function pointer