Why can the "Range-based for loop" ( for (declaration:range) statement) be used only in the main function?

Question

Range-based for loop

Answer 1

Solution 1
void range_for (string arr) {
for (char c : arr)
cout << c << endl;
}

template <size_t X>
void range_for (int (&arr) [X]) {
for (int c : arr)
cout << c << endl;
}

int main ()
{
string str {"Hello!"};
int a [] = {1, 2, 3};

range_for (str); //It works.

for (int n : a)
cout<< n << ' '; //It works

range_for (a); // This function now uses the address of the array as well as its size.

Answer 2

Solution 2
Turn the array into a vector

Answer 3

Thanks, Checker 8763! I appreciate your help!

Answer 4

We might say that:
"Range-based for loop could be used anywhere, just don't forget to work with a variable with a fixed size. If a function implements a range-based for loop inside and the argument used as range is an array, it will show an error, because the size information is lost."

Answer 5

C++. I know they could be used anywhere, I'm just asking for this kind of syntax. Whenever I try to use it, an error shows up.

Answer 6

Thanks!
I'm trying this:

void range_for (string arr) {
for (char c : arr)
cout << c << endl;
}

void range_for (int arr []) {
for (int c : arr)
cout << c << endl;
}

int main ()
{
string str {"Hello!"};
int a [] = {1, 2, 3};

range_for (str); //It works.

for (int n : a)
cout<< n << ' '; //It works

range_for (a); // error (''This
Range-based for statement requires a suitable begin function and none was found'')

}

Answer 7

According to my research, the "range-based for" need the size of argument. Since passing an array as a function argument means passing a pointer to the first element and not the array itself, that fact leads to an error while using this kind of syntax.

Answer 8

This is what I found:

https://stackoverflow.com/questions/7939399/how-does-the-range-based-for-work-for-plain-arrays

I'm sorry that I thought this question was simpler than it is.
I'm not that perfect in c++ but I try to help at best!