Returning arrays from a function

[sdoug041]

hello. I am working on a c++ assignment right now, and my job is to write a sub-program that will fill two arrays with random numbers (1-10), then ask the student 10 arithmetic questions (either multiply or divide depending on a previous choice) and store the answers in a third arrray. I come across problems when trying to call the function and returning the array from the function. (the answers)

in the main () i have something like

int student_answers [10];
student_answers [10] = run_test ();

the above 3 lines are an attempt to call the function but I have limited knowledge about arrays.

in the sub-program itself I have something like:

int run_test (int verification)
... bunch of code... stores answers in answer[10]
return (answers[10]);

is ths the correct way of returning an array?

 

[Mark44]

No. A C/C++ function can't return an entire array. It can return a pointer to an array, or the address of an existing array can be passed as a parameter to the function, and when the function exits, the array will have its values filled in. (BTW, the term subprogram is not usually used in C/C++; the term most often used is function.)

Look at your text and/or notes to see how arrays are passed as parameters in functions.

in the sub-program itself I have something like:

int run_test (int verification)
... bunch of code... stores answers in answer[10]
return (answers[10]);

There are several errors in the function skeleton above.

1. run_test returns an int, a single integer value. Your intent was to return an entire array (which you can't do), so there is a mismatch between what your function returns and what your previous statement intends to do.
   
   student_answers [10] = run_test ();
2. In the call to run_test just above, there are no parameters, but in your function definition, there is an int parameter, verification.
3. Where you said "stores answers in answer[10]" there are two problems: For an array with 10 elements, the last element is answer[9], not answer[10]. Also, you are apparently trying to put all your answers in one element of your array, not in answer[0], answer[1], ..., answer[9].
4. Your return statement attempts to return a single value in your array, answer[10]. As already noted, this is not an element in your array. Furthermore, it is not an array: it is a single integer value.

 

[quicknote]

Hello there,

First of all, great job on working on your assignment and trying to understand how to return arrays from a function. Your approach is on the right track, but there are a few things that can be improved.

In your main() function, you are attempting to call the run_test() function and assign the returned array to the student_answers array. However, this line of code is incorrect: student_answers[10] = run_test();. This is because you are trying to access the 11th element of the array (remember that arrays start counting at 0), which does not exist. Instead, you should simply write: run_test(student_answers);. This will pass the student_answers array as a parameter to the run_test() function.

In your run_test() function, you are on the right track by declaring it as an int function and returning an array. However, the way you are returning the array is incorrect. The return statement should simply be: return answers;. This will return the entire array to the caller.

Additionally, since you are passing the student_answers array as a parameter to the run_test() function, you do not need to declare the answers array inside the function. Instead, you can simply use the student_answers array to store the answers.

I hope this helps clarify any confusion you may have had about returning arrays from a function. Keep up the good work!