Passing a structure to a function.

[apedosmil8]

I am having trouble trying to display a function in my program.

The program basically opens up a binary file and reads the last name, first name, GPA etc...

What works in main is if I do a cout <<ar[i].last; The last name will display as for everything else. I need to have this work in the function but I am completly lost.

#include <iostream>
#include <iomanip>
#include <fstream>

using namespace std;

struct Tstudent
{
char last[40];
char first[40];
char ID[10];
double gpa;
int score;
};

void dispStudent(Tstudent stu);

int main()
{//start main
cout << setiosflags(ios::left);
ifstream infile;
Tstudent stu;


Tstudent ar[100];

int i = 0;
infile.open("file", ios::binary);

if(infile.fail())
{
cout <<"\n\nError: FILE NOT FOUND!";
exit(1);
}

infile.read((char *) &ar[i], sizeof(Tstudent));



while(!infile.eof())
{
i++;
infile.read((char *) &ar[i], sizeof(Tstudent));

}


dispStudent(ar[i]); //problem area, not sure what to put here

infile.close();

}

/************************/

void dispStudent(Tstudent stu)
{//start main




}//end main

[nmadct]

What you have should work, in the dispStudent function you can display the last name like this:

cout << stu.last;

However, I'd do it a little differently. When you declare the function dispStudent, instead of declaring it like this:

void dispStudent(Tstudent stu) /* passes a copy of the entire struct */

I would declare it like this:

void dispStudent(Tstudent * stu) /* passes a pointer to the struct */

Passing a pointer is much more efficient than copying the whole struct, especially when the struct is, like yours, more than trivial in size. With this declaration, the last name field can be accessed from within the dispStudent function like this:

cout << stu->last;

You can now call dispStudent like this:

Tstudent ar[100];
dispStudent(&ar[i]);

[apedosmil8]

Thank you for the reply, I tried what you said just to try it and thanks!

The problem is I can't use that for my program. We have to follow the assignment :(

I have created the function and I have created the display function.

What I need to do is make it in order... I believe I need to do a while loop with the last name since the file starts with a last name.

What would be your suggestion to display the loop in ascending order.

#include <iostream>
#include <iomanip>
#include <fstream>

using namespace std;

struct Tstudent
{
char last[40];
char first[40];
char ID[10];
double gpa;
int score;
};

void dispStudent(Tstudent stu);

void dispAll(Tstudent ar[], int count);

int main()
{//start main
cout << setiosflags(ios::left);
ifstream infile;
Tstudent stu;


Tstudent ar[100];

int i = 0;
infile.open("stinfo", ios::binary);

if(infile.fail())
{
cout <<"\n\nError: FILE NOT FOUND!";
exit(1);
}

infile.read((char *) &ar[i], sizeof(Tstudent));



while(!infile.eof())
{
i++;
infile.read((char *) &ar[i], sizeof(Tstudent));

}
int count;
count = i;

dispAll(ar, count);


infile.close();

}

/************************/

void dispStudent(Tstudent stu)
{//start function
cout << setiosflags(ios::left);
cout << "\nLast: " << stu.last <<" First: " <<stu.first <<" ID: " <<stu.ID;
cout << "\n\nGPA: " <<stu.gpa << " Score: " <<stu.score << endl;
cout << "\n**************************** New Entry ****************************\n";
}//end function


void dispAll(Tstudent ar[], int count)
{//start function

int i;

for(i = 0; i < (count-1); i++)
{
dispStudent(ar[i]);
}

}//end function

[gpraghuram]

HI,
I have one doubt in your code.
When u are reading the value from the file using the structure why are you typecasting to char* and reading.
I think it may cause you problem.

Thanks
Raghuram