Great work! In R, a function always returns a single value (an object). That object can be a number, string, vector, list, data frame, or anything else.

What happens if you don't explicitly define a return statement? In that case, R takes the last generated value/object inside the function and returns it as a result. Consider the following version of the count_age() function:

count_age <- function(birth_year){
  current_year <- as.numeric(format(Sys.time(), "%Y"))
  current_year - birth_year
}

This will return the exact same result as the function you defined in the last exercise with the explicit return statement. In this version, R simply takes the value of current_year - birth_year and returns it to the caller.

Generally, it's recommended that you explicitly use the return keyword in your functions. This makes the code more readable.