Referencing a structure inside an array

This is a discussion on Referencing a structure inside an array within the C Programming forums, part of the General Programming Boards category; Hi, I'm working on a program to sort students by last name, first name, middle initial, gpa, etc. I've defined ...

  1. #1
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    May 2010
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    11

    Referencing a structure inside an array

    Hi,

    I'm working on a program to sort students by last name, first name, middle initial, gpa, etc. I've defined a data structure called "Student."

    Code:
    typedef struct
    {
       char last[21];
       char first[11];
       char mi;
       double gpa;
    }Student;
    I wrote a function which will scan a line of a text file, then fill in each part of the "Student" data structure, and return a variable (type Student), called studentx.

    Now, I need to declare an array of type "Student" and input "studentx" into each index, after it comes out of the function. Keep in mind every time I call the function, a different "studentx" will be returned.

    My first problem is that I don't think I'm defining it right. I have this

    Code:
    struct Student studentList[1000];
    but I get the error "studentrpt.c:32: error: array type has incomplete element type"

    any ideas?

    to input my "student" variable into the studentList array, here's what I have. (it says "i" because it's in a loop, but i'm not worried about the loop right now, so don't worry about it either. As stated, the "getInfo" function returns type Student.

    Code:
    studentList[i] = getInfo(input, student);
    Now say I want to print a specific thing from a specific index of my studentList array, for example, I want to print the first name of the student in the 27th index of the array. How do I do that? What variable do i put in the printf statement?

    is it this?

    studentList[27].first

    Any help is appreciated, thanks!

  2. #2
    ATH0 quzah's Avatar
    Join Date
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    Posts
    14,826
    The only difference between accessing an array element and a single variable instance is the addition of [ here ].
    Code:
    struct foo onething, arrayofthing[ 5 ];
    ...
    onething.bar = baz;
    arrayofthing[ here ].bar = baz;
    Quzah.
    Hope is the first step on the road to disappointment.

  3. #3
    Registered User
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    1,485
    You don't need the 'struct' part of your array declaration since you used typedef in the struct.

    Code:
    Student studentList[1000];
    This should do it.

    is it this?

    studentList[27].first
    Yes, that's it.

    You mention that your getInfo function will return a new instance of Student in each call, which means that you are allocating memory inside the function for each struct. But, you have already set aside memory for 1000 Student structs, you'll need to pass a pointer to Student to the array, and make it an array of Student pointers.

    Or, do as you do now, but pass the entire studentList as argument to your getInfo function, and fill it in, in place directly from the file.

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