函数指针学习与理解
//函数指针学习与理解
/*
Makefile:
-------------------------------
callback.exe : callback.c
gcc callback.c -o callback.exe
clean:
rm callback.exe
*/
#include <stdio.h>
#include <stdlib.h>
//函数指针类型的声明
typedef int (*CallBackHandle)(int a, int b);
int add(int a, int b)
{
return a + b;
}
int minus(int a, int b)
{
return a - b;
}
//全局的函数指针
CallBackHandle handle;
//作业处理函数
void process()
{
printf("Please input two number:\n");
int a,b;
scanf("%d", &a);
scanf("%d", &b);
printf("\n%d op %d is ", a, b);
if(handle != NULL)
printf("%d\n", handle(a, b));
else
printf("unknow\n");
}
//初始化全局函数指针
void iniHandle()
{
redo:
printf("Please select a op function:\n");
printf("Add 1\n");
printf("Minus 2\n");
int k;
scanf("%d", &k);
switch(k)
{
case 1:
handle = add;
printf("Add selected.\n");
break;
case 2:
handle = minus;
printf("Minus selected.\n");
break;
default:
printf("Function Select Error!\n");
goto redo;
}
}
//初始化全局函数指针的另外一个版本
void iniHandle_2()
{
printf("add: %d\n", add);
printf("minus:%d\n", minus);
int addr = 0;
scanf("%d", &addr);
handle = (void*)addr;
printf("Now the handle is %d\n", handle);
}
//程序入口点
int main()
{
iniHandle_2();
process();
}
评论