如何让c语言使用结构体近似模拟c++中的类

如今统治市场的主流编程语言，如c++，java，大都是面向对象类型的编程语言。

而众所周知，c语言是面向过程的编程语言，但是它拥有一个类似于类的结构，叫做结构体，主要的区别在于结构体无法定义函数。

因此，为了c语言的结构体近似模拟类，我们可以在结构体中定义函数指针。

下面这个例子，是最常用的计算学生分数平均数的c++类模版：

#include <cstdio>
#include <iostream>
#include <cstdlib>

#define LINE for (i = 0 ; i < 60 ; i++) {printf("-");}printf("\n");
#define SPACE for (i = 0 ; i < 20 ; i++) printf(" ");

using namespace std;

class Student
{
public:
  double stuAvg(double score[]);
  int num;
  char name[10];
  double score[3];
  double average;
};

double Student::stuAvg(double score[]){
  double sum = 0.0;
  double average = 0.0;
  for (int i=0 ; i < 3 ; i++)
  {
    sum += score[i];
  }
  return average = sum/3;
}

int main(void){
  Student stu1;
  for (int i = 0 ; i < 3 ; i++)
  {
    scanf("%lf",&stu1.score[i]);
  }
  stu1.num = 1001;
  memset(stu1.name,0,sizeof(stu1.name));
  strcat(stu1.name,"Peter");
  stu1.average = stu1.stuAvg(stu1.score);

  //Output Part

  printf("NUM");
  SPACE;
  printf("NAME");
  SPACE;
  printf("AVERAGE");
  printf("\n");
  LINE;
  printf("%d",stu1.num);
  SPACE;
  printf("%s",stu1.name);
  SPACE;
  printf("%.2lf",stu1.average);
  printf("\n");
  LINE;
  return 0;
}

接下来我们使用结构体模拟上例中类的作用：

#include <stdio.h>    
#include <stdlib.h>  
  
#define LINE for (i = 0 ; i < 60 ; i++) {printf("-");}printf("\n");  
#define SPACE for (i = 0 ; i < 20 ; i++) printf(" ");    
  
struct Student{  
    double (*stuAvg)(double score[]);  
    int num;  
    char name[10];  
    double score[3];  
    double average;  
};  

double Calc_Avg(double score[]){  
    int i = 0;  
    double sum = 0.0;  
    double average = 0.0;  
    for (i=0 ; i < 3 ; i++)  
    {  
        sum += score[i];  
    }  
    return average = sum/3;  
}  

void main(void){  
    int i = 0;
    struct Student stu1;  
    for (i = 0 ; i < 3 ; i++)  
    {  
        scanf("%lf",&stu1.score[i]);  
    }  
    stu1.num = 1001;  
    memset(stu1.name,0,sizeof(stu1.name));  
    strcat(stu1.name,"Peter");  
    stu1.stuAvg = Calc_Avg;  
    stu1.average = stu1.stuAvg(stu1.score);  
    
    //Ouuput Part  
    
    printf("NUM");  
    SPACE;  
    printf("NAME");  
    SPACE;  
    printf("AVERAGE");  
    printf("\n");  
    LINE;  
    printf("%d",stu1.num);  
    SPACE;  
    printf("%s",stu1.name);  
    SPACE;  
    printf("%.2lf",stu1.average);  
    printf("\n");  
    LINE;  
    return;  
}