In the last line inside for loop, how does "element" initiate itself and how does for loop proceeds further and terminates.plz help

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Hi @blog8966734684 welcome to the forum.

Your question, just so it’s also in the thread, is:

In the last line inside for loop, how does “element” initiate itself and how does for loop proceeds further and terminates.plz help

You’ve defined the for loop like so:

for (int element : first_three_multiples(8)) {
    std::cout << element << "\n";
}

This type of for declaration in C++ is a range-based for loop.

You’ve already declared, on lines 5-11 of your code (as per your screenshot), the function first_three_multiples(). This takes an int num, and returns a vector<int>.

Let’s take a look at your for loop in more detail.

for (int element : first_three_multiples(8)) {
In this line, you’re declaring a new variable - int element - to take a value of a single item from the range - first_three_multiples(8) - each iteration.

This is where your variable element has been declared, and each iteration of the for loop gives it the appropriate value from the vector returned by first_three_multiples. The variable only exists within the for loop, though - you wouldn’t be able to use the element variable anywhere else without declaring it first outside the loop.

For example, both of the for loops below do the same thing:

#include <iostream>
#include <vector>

std::vector<int> first_three_multiples(int num) {
  std::vector<int> multiples{num, num * 2, num * 3};
  return multiples;
}

int main() {
  
  std::cout << "Range-based for:\n";
  for (int element : first_three_multiples(8)) {
    std::cout << element << "\n";
  }
  
  std::cout << "\n\n 'Regular' for:\n";
  std::vector<int> multiples_of_8 = first_three_multiples(8);
  
  for (int i = 0; i < multiples_of_8.size(); i++) {
    std::cout << multiples_of_8[i] << "\n";
  }  
  
}

This produces:

Range-based for:
8
16
24


'Regular' for:
8
16
24

Does that help at all?

1 Like

thanks for your response…got it.
one more que… it means that range based for loop can only be used in case of vectors?

1 Like

No, you can use a range-based for loop with any type that is a sequence of elements. For example:

#include <iostream>
#include <string>

int main() {
  std::string message = "Hello, world!";
  for (char c : message) {
    std::cout << c << "\n";
  }
  
}

Produces:

H
e
l
l
o
,

w
o
r
l
d
!
1 Like

thanks a ton…the explanations really worked…

1 Like

No worries. :slight_smile: