# typedef指针

## 1.简单的函数指针的应用

形式1：返回类型(\*函数名)(参数表)

```c
char (*pFun)(int);   
char glFun(int a){ return;}   
void main()   
{   
    pFun = glFun;   
    (*pFun)(2);   
}
```

## 2.使用typedef更直观更方便

形式1：typedef 返回类型(\*新类型)(参数表)

```c
typedef char (*PTRFUN)(int);   
PTRFUN pFun;   
char glFun(int a){ return;}   
void main()   
{   
    pFun = glFun;   
    (*pFun)(2);   
}
```

## 3.例子说明

### **typedef定义函数指针**

```c
typedef int (*FP_CALC)(int,int);//定义一个函数指针类型  

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 div(int a, int b)  
{  
    return b ? a/b : -1;  
}  

//定义一个函数，参数为op，返回一个指针,该指针类型为拥有两个int参数、  
//返回类型为int的函数指针。它的作用是根据操作符返回相应函数的地址  
FP_CALC calc_func(char op)  
{  
    switch( op )  
    {  
    case '+':  
        return add;  
    case '-':  
        return sub;  
    case '*':  
        return mul;  
    case '/':  
        return div;  
    default:  
        return NULL;  
    }  
    return NULL;  
}
```

### **返回函数指针，直接定义**

```c
//s_calc_func为函数，它的参数是 op，     
//返回值为一个拥有两个int参数、返回类型为int的函数指针    
int (*s_calc_func(char op)) (int , int)  
{
    return calc_func(op);  
}
```

### 使用

```c
FP_CALC fp = calc_func(op);  
int (*s_fp)(int,int) = s_calc_func(op);//用于测试
```


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