Thread: array type has incomplete element type

Originally Posted by CommonTater

Code:

void SelectionSort(struct employee eTable[MaxSize], int numEntries, FILE *outFile){

Lose the highlighted part and try it again... just use eTable[]

I believe that's legal, with some caveats:
C89:
MaxSize must be a constant integer expression -- an integer literal or an expression that is an integer literal (e.g 3 + 4), or a #define of either of those.

C99:
MaxSize must be a constant integer expression (like C89) or
MaxSize is an integer variable that is visible at the time of declaration (e.g. global variable/const) or
MaxSize is an integer variable that comes before eTable in the parameter list.

It sure don't work in my compiler....

In absolutely no way did I cheat or "scoop and poop". This is 100% my code, I just don't understand how to use templates so I'm trying to go off what he has in his notes, which apparently as I look through here is only a C++ definition of templates. We're given an entire notebook of his notes to use as a reference. I don't like being branded as a cheater because I used something in the wrong way. He has examples of C code mixed in with examples of C++ code, and I just didn't realize that I was looking at the C++ implementation.

How do you implement templates in C? I can't find anything other than C++

@philgrek: I recommend going to your TA or prof for a better explanation. The instructions you posted don't really give me a clear idea of what he/she wants, and I'm not C++ expert.

@Tater: Try the following and see if it works. I compiled with "gcc -Wall --std=c99 -pedantic main.c", no errors or warnings.

Code:

#include <stdio.h>
#include <stdlib.h>

void print(int size, int x[size])
{
    int i;

    for (i = 0; i < size; i++) {
        printf("%d ", x[i]);
    }
    putchar('\n');
}

int sum(int size, int x[size])
{
    int i, sum;

    sum = 0;
    for (i = 0; i < size; i++) {
        sum += x[i];
    }

    return sum;
}

int main(void)
{
    int size = 5;
    int array[] = {1, 2, 3, 4, 5};

    printf("Data: ");
    print(size, array);
    printf("Sum: %d\n", sum(size, array));

    return 0;
}

Originally Posted by philgrek

How do you implement templates in C? I can't find anything other than C++

There are no templates in C. You can simulate them a bit with function pointers and void pointers for the data types, but it's a lot of fairly messy work. I really think you need some serious clarification from your prof on this.

Unfortunately, I have to turn this in in an hour. I'm not intending to use C++ at all, entirely C. Ugh. Oh well

Yeah, I'm just abandoning the template option. Other than that, the program runs pretty smoothly. Thanks for all the help! I really appreciate it

Originally Posted by philgrek

How do you implement templates in C?

You can't. C does not support classes, templates and a whole whack of other C++ stuff... You can write code that, in some ways, works like a lot of C++ stuff... but it's still C code.

Originally Posted by anduril462

@Tater: Try the following and see if it works. I compiled with "gcc -Wall --std=c99 -pedantic main.c", no errors or warnings.

The compiler accepts it, but from what I've seen the value in the [] brackets is ignored... I could be wrong (happens sometimes).

Originally Posted by MK27

I hate it when

Have you been told today?

Originally Posted by CommonTater

The compiler accepts it, but from what I've seen the value in the [] brackets is ignored... I could be wrong (happens sometimes).

No, you're right, at least for 1-d arrays. Like any array in a function definition, the degradation to a pointer makes the the size in the leftmost set of [ ] unnecessary (the other sizes are needed to compute the space between, e.g. &arr[0][0] and &array[1][0]). For a 1-d, there's only 1 set of [ ] and it doesn't need a size. For multi-dimensional arrays however, the variable size thing works, AFAIK. Here's a sample 2-d array program to test:

Code:

#include <stdio.h>

void print(int size1, int size2, int x[size1][size2])
{
    int i, j;

    for (i = 0; i < size1; i++) {
        for (j = 0; j < size2; j++) {
            printf("%4d ", x[i][j]);
        }
        putchar('\n');
    }
}

int sum(int size1, int size2, int x[size1][size2])
{
    int i, j, sum;

    sum = 0;
    for (i = 0; i < size1; i++) {
        for (j = 0; j < size2; j++) {
            sum += x[i][j];
        }
    }

    return sum;
}

int main(void)
{
    int size1 = 3;
    int size2 = 5;
    int array[3][5] = {
        { 1,  2,  3,  4,  5},
        { 6,  7,  8,  9, 10},
        {11, 12, 13, 14, 15}
    };

    print(size1, size2, array);
    printf("Sum: %d\n", sum(size1, size2, array));

    return 0;
}