I am trying to return a certain array from a function that when called, assigns value to the array
The function should go something like this:
int arr[10];
int values[10] = {1,2,3,4,5,6,7,8,9};
for (int i =0; i<10; i++)
{
arr[i] = values[i];
}
How do I translate this code into a function?
using namespace std;
As far I know, you shouldn't be looking to return an array from a function... like, ever. What I would do instead is pass the names of the arrays to the function and have it process the contents in whatever way you need it to. In your case, you're just copying them so something like this should work:
#include <iostream>
using namespace std;
void copy_array (const int [], int []); //function prototype
int main()
{
//Your arrays
int arr[10];
int values[10] = {1,2,3,4,5,6,7,8,9};
//Function call
copy_array(values, arr);
//Display contents of array
for(int i =0; i<10; i++){
cout << arr[i] << " " ;
}
return 0;
}
//Function definition
void copy_array (const int values[], int arr[]){
for (int i =0; i<10; i++){
arr[i] = values[i];
}
}
Output
1 2 3 4 5 6 7 8 9 0
Also, your array size should be a constant integer variable.
you probably don't want to return arrays like never, because it could mean a lot of useless copy, which slows down your program, but you could always write a function that copies values from one array to another
#include <iostream>
void assignarray(int *dest, int *src, size_t size)
{
for (size_t i = 0; i < size; ++i)
{
dest[i] = src[i];
}
}
int main()
{
int arr[10];
int values[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
assignarray(arr, values, sizeof(values) / sizeof(int));
for (size_t i = 0; i < 10; i++)
{
std::cout << values[i] << " ";
}
}
output:
1 2 3 4 5 6 7 8 9 10
std::array.
1 2 3 4 5 6 7 8 9 10 . The 4th number differs from your output.
std::vector. One thing you should realize -- introducing pointers does not mean a "code speedup". Too many still think that using pointers will outperform a compiler's optimizer. Also, the comment of returning an array -- even though arrays cannot be returned, that basic comment is not true about returning will slow down the code. Compilers use, and in some cases, mandated to have return-value-optimization, thus all of those fears from 20 years ago about returning large objects "slowing down" a program are for the most part, gone.std::array the first time. Second, the amount of functionality has nothing to do with using a vector or not. If the functionality of what vector provides creates a clean, non-buggy program, then it should be used.Return type of a function cannot be an array.
However, array can be member of a class, and class can be return type of a function, so it is possible to return a class object which wraps the array. The standard library has a template for such array wrapper. It is called std::array.
That said, returning an array (wrapped within a class) is not necessarily a good design. Sometimes it is better to let the caller create the container - and indeed, they can choose the type of the container that they wish to use - and pass that into a template function to be filled. Here is an example of accepting a range:
template<class Range>
void fill(Range& r) {
assert(std::ranges::distance(r) == 10);
int values[10] = {1,2,3,4,5,6,7,8,9};
int i = 0;
for (auto& e : r)
{
e = values[i++];
}
}
// example
int arr[10];
fill(arr);
std::vectorinstead of arrays.std::array, not dumb arrays, which are not copyable.