函式指標

範例一

#include <stdio.h>
#include <stdlib.h>

int add (int a, int b)
{ return a+b;
}

int sub (int a, int b)
{ return a-b;
}

int mul (int a, int b)
{ return a*b;
}

int divv (int a, int b)
{ return a/b;
}

int main (void)
{
    int c=20,d=2;
    int e;
    int (*test)(int c, int d)=&add; //函式指標, 預設值為 add
    char key;
    
    printf("Press +,-,*,/ for add, sub, mul, div\n"); 
    key=getch();
    switch(key)
    {
        case '+':
            test=add; break;
        case '-':
            test=sub; break;
        case '*':
            test=mul; break;
        case '/':
            test=divv; break;
    }
    e=test(c,d);
    printf("%d\n",e);
    system("pause");
}

範例二

#include <stdio.h>
#include <stdlib.h>

#define ARRAY_SIZE(A) (sizeof(A)/sizeof(A[0]))

typedef struct _BtnAction *BtnAction;
typedef struct BtnAction
{
 char key;
 int (*func)(int, int);
}
_BtnAction;

int BtnAdd(int a, int b)
{
 return a+b;
}

int BtnSub(int a, int b)
{
 int tmp;
 if (b > a)
 {
  tmp=a;
  a=b;
  b=tmp;
 }
 printf("a-b=%d\n", a-b);
 return a-b;
}

_BtnAction BtnAct[]=
{
 { '+', BtnAdd},
 { '-', BtnSub} 
};

int main (void)
{
 char key;
 int i=0;
 int ret=0;
 printf("Press +,-,*,/ for add, sub, mul, div\n"); 
 key=getchar();

 
 for (i=0; i<ARRAY_SIZE(BtnAct); i++)
 {
  if ( key == BtnAct[i].key)
  {
   ret=BtnAct[i].func(5, 3);
   break;
  }
 }

 printf("ret=%d\n", ret);
  
 return 0;
}