#include "stdio.h"typedef int (*FUN)(int x,int y);FUN m_fun;int add(int x,int y){    return x+y;}int sub(int x,int y){    return x-y;}enum method{    Add=1,    Sub};void ChooseFun(method md,int x,int y){    switch(md)    {    case Add:        m_fun=add;        break;    case Sub:        m_fun=sub;        break;    default:        m_fun=add;    }    printf("X+Y=%d",m_fun(x,y));}int main(){    ChooseFun(Add,3,4);    getchar();}