OOP344-Jason Quan C/C++ Programs & notes-20102

pointer to functions

A pointer can be used to point to anything. Therefore you can also use it to point to a function, here’s an simple c program that uses pointer to function:

#include<stdio.h>
void windows(char,int);
void mac(char,int);
int main(void) {
  void (*platform)(char,int); /* this a declaration of a function pointer with 
a argument of char and int*/
  char name[30];
  int option;
  printf("Please enter your name: ");
  scanf("%s", &name);
  do{
  printf("Which platform 1.Windows, 2.Mac:");
  scanf("%d", &option);
  platform = (option < 2) ? windows : mac; /* this line assign where the 
platform pointer should point to.*/  
  (option > 2||option<1) && printf("error: pick 1 or 2\n"); /*Lazy Evaculation*/
  }while(option<1||option>2);
  platform(name , option);
  
  return 0;
}
void windows(char* str,int n) {
  printf("%s you've choosen option %d, you are a Windows user.\n",str,n);
}
void mac(char* str,int m) {
  printf(" %s you've chosen Option %d, you are Mac user.\n",str, m);
}

In this program two functions are declared: void Windows(char *str,int n) and void Mac(char *str ,int m) they both return void. But the output a line. Within the main() a void pointer call platform is declared with two arugments( char, int) which are values types that will be pasted to the corrsponding functions which is determine by this line : platform = (option < 2) ? windows : mac;

If the user chooses option 1 platform will be set to point to the windows function else Mac fun ction otherwise. To call the function, you would call it using the pointer platform by use a line: platform(name , option); this line will call the function.