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;
}