Not declared in scope C++ [Arrays]

Question

I have a quick question. Trying to create a method to print out an array, however, the compiler is telling me that it isn't declared in the scope.

Here's my code:

int main() {
    int theArray[10] = {41, 23, 43, 12, 43, 23, 12, 41, 29, 102};
    printArray(theArray, 10);
}

Here's my printArray method:

void printArray(int arr[], int size) {
    int i;

   for (i = 0; i < size; i ++) {
       std::cout <<" "<< arr[i];
       std::cout << std::endl;
   }
}

Any clue what I'm doing wrong?

You forgot to declare the function before main.

molbdnilo
– molbdnilo

2016-02-23 06:38:52 +00:00
Commented Feb 23, 2016 at 6:38 — molbdnilo
– molbdnilo, Commented Feb 23, 2016 at 6:38
@molbdnilo, Thank you, sir!

Team41
– Team41

2016-02-23 06:39:36 +00:00
Commented Feb 23, 2016 at 6:39 — Team41
– Team41, Commented Feb 23, 2016 at 6:39

Humam Helfawi · Accepted Answer · 2016-02-23 06:53:26Z

3

Your code is perfectly fine. Just make sure that necessary includes are exist. And the order of the methods:

#include <iostream>
#include <string>

void printArray(int arr[], int size) {
    int i;
    for (i = 0; i < size; i++) {
        std::cout << " " << arr[i];
        std::cout << std::endl;
    }
}

int main() {
    int theArray[10] = { 41, 23, 43, 12, 43, 23, 12, 41, 29, 102 };
    printArray(theArray, 10);
    return 0;
}

Or use forward declaration:

#include <iostream>
#include <string>

void printArray(int arr[], int size);

int main() {
    int theArray[10] = { 41, 23, 43, 12, 43, 23, 12, 41, 29, 102 };
    printArray(theArray, 10);
    return 0;
}

void printArray(int arr[], int size) {
    int i;
    for (i = 0; i < size; i++) {
        std::cout << " " << arr[i];
        std::cout << std::endl;
    }
}

However, you may write it in more C++ modern Style:

1) Using templated function :

#include <iostream>
#include <string>
#include <array>
template<std::size_t N> void printArray(std::array<int, N> x) {
    for (auto const& item:x){
        std::cout << " " << item << std::endl;
    }
}

int main() {
    std::array <int, 10> theArray{ { 41, 23, 43, 12, 43, 23, 12, 41, 29, 102 } };
    printArray<10>(theArray);
    return 0;
}

2)The better by using iterators:

#include <iostream>
#include <string>
#include <array>
template<typename Iterator> void printArray(Iterator beg, Iterator end) {
    for (auto it = beg; it != end; it = std::next(it)){
        std::cout << " " << *it << std::endl;
    }
}

int main() {
    std::array <int, 10> theArray{ { 41, 23, 43, 12, 43, 23, 12, 41, 29, 102 } };
    printArray(std::begin(theArray), std::end(theArray));
    return 0;
}

edited Feb 23, 2016 at 6:53

answered Feb 23, 2016 at 6:40

Humam Helfawi

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3 Comments

user4581301 Over a year ago

Go with option 1. The forward declare doesn't get you anything here except another line of code to be maintained and weird linker errors if you change the function's prototype and not the forward declaration.

Fantastic Mr Fox Over a year ago

Or use a std::vector i know the memory storage is different, but will likely be more useful thing to learn in this scenario.

Humam Helfawi Over a year ago

use std::vector just when the number of elements is not constant.

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