Array Of Structures

[joli 0]

This is another way of doing things instead of using objects as posted yesterday in http://forum.sourceboost.com/index.php?showtopic=5515

// file: students.h

#ifndef _STUDENTS_H_
#define _STUDENTS_H_

typedef unsigned char uchar;

#define STUDENTS    64

// S T U D E N T   D A T A   S T R U C T

typedef struct
{
    uchar s_id;                                 // id
    uchar s_age;                                // age
}Student;

extern Student StuList[STUDENTS];               // turn it global / not needed if we plan to use it only by the students.cpp module

#endif

// file: students.cpp

#include <system.h>
#include "students.h"

Student StuList[STUDENTS];                      // array of struct

void AddStudent( uchar *pstudent, uchar index ) // add student
{
    StuList[index].s_id  = *pstudent++;
    StuList[index].s_age = * pstudent;
}

void main()
{
    uchar adata[2];
     
    for( uchar i=0; i<STUDENTS; i++ )           // all 64
    {
        adata[0] = i+1;                         // id data to be stored
        adata[1] = i+1;                         // age data to be stored
        
        AddStudent( adata, i );                 // add_student
    }
}

The advantage of this approach is that the entire collection consumes 128 bytes instead of 192 bytes when objects is used.

 

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Edited July 30, 2016 by joli

[joli 0]

A more elegant way to do the same...

// header file

#ifndef _STUDENTS_H_
#define _STUDENTS_H_

typedef unsigned char uchar;

#define STUDENTS    64

// S T U D E N T   D A T A   S T R U C T

struct Student
{
    uchar s_id;                                 // id
    uchar s_age;                                // age
    
    void AddStudent( uchar *pstudent )          // add function member
    {
        s_id  = *pstudent++;
        s_age = *pstudent;
    }
};

extern Student StuList[STUDENTS];               // turn it global if need

#endif

// c file

#include <system.h>
#include "students.h"

Student StuList[STUDENTS];

void main()
{
    uchar adata[2];
     
    for( uchar i=0; i<STUDENTS; i++ )       // all 64 elements
    {
        adata[0] = i+1;                     // data to be stored
        adata[1] = i+1;
        StuList[i].AddStudent( adata );
    }
}

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Edited July 30, 2016 by joli

[joli 0]

I did an atempt to use this in a real application by using several lists of structures but the compiler boostc/bostc++, failed.
After several tests i concluded that the compiler do doesn't like to have "methodes" inside of the structure.
So, until better oppinion, i believe that this is a compiler issue.

 

Modifications:

1. delete AddStudent( uchar *pstudent ) "methode" inside of structure.

2. instead of StuList.AddStudent( adata ), StuList.s_id = data[0] and StuList.s_age = data[1] should be used.

 

 

br