Quick Question about Homework

[Cameron Taylor]

Ok, so I had an assignment due a few days ago and I typed it all up myself without any help (pretty proud of myself at the time), but my instructor took off 4 out of 20 points because I didn't make it a void function.

Here is the code:

#include <stdio.h>
#define MAXARRAY 10

double extend(double[], double[], double[], int);

int main(){

    double price[MAXARRAY] = {10.62, 14.89, 13.21, 16.55, 19.62, 9.47, 6.58, 19.32, 12.15, 3.99};
    double quantity[MAXARRAY] = {4, 9.5, 6, 7.35, 9, 15.3, 3, 5.4, 2.9, 4.9};
    double amount[MAXARRAY];
    int i;
    
    extend(price, quantity, amount, MAXARRAY);
    
    for (i = 0; i < MAXARRAY; i++)
        printf("The product of price %d and quantity %d is amount %5.2f\n", i+1, i+1, amount[i]);

    return 0;
}

double extend(double price[], double quantity[], double amount[], int max){

    int i;
    double product;
    double *p, *q;

    p = price; q = quantity;

    for (i = 0; i < max; i++)
    
        amount[i] = *p++ * *q++;
        amount[i] = product;
    
        return (product);
}

The assignment doesn't say "extend" needed to be a void function. All it said is that the function "extend" needed to have three arrays passed to it.

This is what my instructor said:

extend should be a void function. You even call it as a void function! What do you think the variable product is doing in the function extend?

Not trying to call him out or anything, but just wondering why extend() needs to be a void function. The program works fine the way it is. It displays the product of the two arrays for each element just like the program asks.

Is it just sloppy coding?

[xwielder]

Yes, it'll work fine, but there's no reason for a return value because you're not assigning the return value of extend() to anything in main(). Since you're not using the return value, just make extend() a void.

[Cameron Taylor]

Yes, it'll work fine, but there's no reason for a return value because you're not assigning the return value of extend() to anything in main(). Since you're not using the return value, just make extend() a void.

Oh ok, so since extend() acts like a void function it would of been proper to call it a void function. I believe what I was thinking is that it needed to be called "double" since the array amount[] was being assigned double values, and I thought anything other than void needed a return value other than "0". Just a rookie mistake on my part, but I didn't think it was worth an 80% grade

[Adak]

Your instructor is correct. Your program doesn't "catch' the value it returns, and there's no sense in returning anything from extend, in any case.

It's like in football - making a great pass is fine, but it's useless to make the pass, unless a teammate is there to receive it.

[whiteflags]

I would mark you 80% just for the dubious use of product.

[Cameron Taylor]

Your instructor is correct. Your program doesn't "catch' the value it returns, and there's no sense in returning anything from extend, in any case.

It's like in football - making a great pass is fine, but it's useless to make the pass, unless a teammate is there to receive it.

Heh, yea. Good analogy. Just sloppy work on my part. Should of done a better job at "proof reading" my code before submitting it just because it worked.

[xwielder]

...and I thought anything other than void needed a return value other than "0"...

No, a void() function can simply "return;", or doesn't even need a "return;" at all. Anything OTHER than a void() function, needs to return whatever you're casting the function as.

Fore example:

// MUST return an int value
int functionOne(int a, int b)
{
     int c = a + b;
     return (c);
}

// Doesn't need to return anything
void functionTwo(int a, int b)
{
     int c = a + b;
     return;
}

// Doesn't need to return anything
void functionThree(int a, int b)
{
     int c = a + b;
}

// This is not correct.  A void() function cannot return any value at all
void functionFour(int a, int b)
{
     int c = a + b;
     return (c);
}

// This is not correct.  You MUST return the same type as the casted function.
char *functionFive(int a, int b)
{
     int c = a + b;
     return (c);
}

and so on and so on...

Hope this helps.

[whiteflags]

void()

Parentheses?

Paretheses have 3 meanings in C: order of operations, casting, and function invocation. You cannot have a function named void, and it is very confusing to think of the return value as or as part of the name.

[xwielder]

Parentheses?

Paretheses have 3 meanings in C: order of operations, casting, and function invocation. You cannot have a function named void, and it is very confusing to think of the return value as or as part of the name.

Parentheses weren't mean as a literal, they were there for easier readability. You can do this though

void someFunction(void)
{
     int c = 123;
}

But you are correct, "void()" is invalid in application.