Newbie question - struct & arrays

This is a discussion on Newbie question - struct & arrays within the C++ Programming forums, part of the General Programming Boards category; I am working on a homework assignment (a simple name and grade sorting program) but I am obviously missing something ...

  1. #1
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    Newbie question - struct & arrays

    I am working on a homework assignment (a simple name and grade sorting program) but I am obviously missing something and am not seeing it.

    Code:
    #include <iostream>
    #include <stdlib.h>
    #include <string.h>
    #define MAX 25
    #define MAXN 10
    
    using namespace std;
    
    int nst; 
    struct NGrade {
           char name[MAX];
           int grade;    
    };
    
    
    int main(){
    
        
    cout << "How many students do you want to process?" << endl;
    cin >> nst;    
    
    struct Ngrade grades[MAXN];
    
    int i;
    for(i=0; i < nst; i++)
    {
        cout << "Enter name for student #" << nst << endl;         
        //cin >> grades[nst].name;         
        
        cout << "Enter grade for student #" << nst << endl;         
        //cin >> grades[nst].grade;     
    }
    
        cout << endl;
        system("PAUSE");
        return EXIT_SUCCESS;
    }
    The error I get is:

    Code:
    22 D:\Dev-Cpp\grade2\main.cpp elements of array `Ngrade grades[10]' have incomplete type 
    22 D:\Dev-Cpp\grade2\main.cpp storage size of `grades' isn't known
    Ideally I had wanted to set it up so that the array quantity (number of names and grades) in the structure was determined by the user at runtime but I can't seem to get it to take a predetermined number of items.

    Simply put I don't understand why it doesn't like my array declaration.


    Thanks in advance from the frustrated and confused,
    n3m0

  2. #2
    Its hard... But im here swgh's Avatar
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    >int nst;

    try to avoid global variables

    >struct Ngrade grades[MAXN];

    That doesnt look right to me. C++ uses classes over structs really.
    Anyway, why would you declare Ngrade again after you have it defined outside main?
    I'm just trying to be a better person - My Name Is Earl

  3. #3
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    Code:
    #include <iostream>
    #include <stdlib.h>
    #include <string.h>
    #define MAXN 10
    
    using namespace std;
    
    int nst; 
    struct NGrade {
           char name[MAX];
           int grades;
    };
    
    
    int main(){
    
        
    cout << "How many students do you want to process?" << endl;
    cin >> nst;    
    
    NGrade student;
    
    student.grades;
    student.name;
    
    int i;
    for(i=0; i < nst; i++)
    {
        cout << "Enter name for student #" << nst << endl;         
        cin >> student.grades;
        
        cout << "Enter grade for student #" << nst << endl;         
        cin >> student.name;
    };
    
        cout << endl;
        system("PAUSE");
        return EXIT_SUCCESS;
    }
    Here i had to change alot but this works, from what i could see you struct syntax was incorrect, you should have a look at how a structure is constructed, don't just take just take my advice tho.
    WhAtHA hell Is GoInG ON

  4. #4
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    Thank you. I did have to do some juggling tho'

    Here's what I have now (thanks again ):

    Code:
    #include <iostream>
    #include <stdlib.h>
    #include <string.h>
    #define MAX 10
    #define MAXN 10
    
    using namespace std;
    
    int nst; 
    struct NGrade {
           char name[MAX];
           int grades;
    };
    
    
    int main(){
    
        
    cout << "How many students do you want to process?" << endl;
    cin >> nst;    
    
    NGrade student[nst];
    
    student[nst].name;
    student[nst].grades;
    
    
    int i;
    for(i=0; i < nst; i++)
    {
        cout << "Enter name for student #" << i+1 << endl;         
        cin >> student[i].name;
        
        cout << "Enter grade for student #" << i+1 << endl;         
        cin >> student[i].grades;
    };
    
        cout << endl;
        system("PAUSE");
        return EXIT_SUCCESS;
    }

  5. #5
    Its hard... But im here swgh's Avatar
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    Your still using global varialbles. 'nst' can be moved inside the main function to make
    it local.
    Why is there a semi-colon after the for loop block?
    I'm just trying to be a better person - My Name Is Earl

  6. #6
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    Quote Originally Posted by swgh
    Your still using global varialbles. 'nst' can be moved inside the main function to make
    it local.
    Why is there a semi-colon after the for loop block?
    The semi-colon was my fault, does't it make a difference (I'm just curious) it works without but if ou do put it in what happens?
    WhAtHA hell Is GoInG ON

  7. #7
    CSharpener vart's Avatar
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    student[nst].name;
    student[nst].grades;
    1. do nothing
    2. access array of students outside its bounds - valide indexes are from 0 till nst-1


    3. You don't check nst value entered by the user. What will happen if he will press 0 or -1 or 100000000 or 1.3 or 'y'? Have you checked your program with all this replies?

    4. why do you need <string.h> ?
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

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