Bid bye to string.characters

As part of the changes, this is one of the most welcomed changes. This change eliminates the necessity for a characters array on String, which means now you can reverse them, loop over them character-by-character, map() and flatMap() them, and more than anything, you can now iterate directly over a String object:

let vowels = "AEIOU"
for char in vowels {
   print(char)
}

This prints the following:

 A , E , I , O, U

Here, you not only get logical iteration through String, but also specific understanding for collection and sequence:

vowels.count , result is 5, no need of vowels.characters.count
vowels.isEmpty , result is false
vowels.dropFirst() , result is "EIOU"
String(vowels.reversed()) , result is "UOIEA"

There is a small improvement to the way characters behave—now you can obtain the UnicodeScalarView straight from the character, whereas earlier, instantiation of a new String was needed.