An additional big advancement is the way String interprets grapheme clusters. Conformity of Unicode 9 gives resolution to this.
The use of extended grapheme clusters for character values in Swift 4 means that concatenation and modification of Strings may cause no affect on a resulting String's character count.
For example, if you append a COMBINING ACUTE ACCENT (U+0301) to the end of the String initialized to "cafe", the resulting String will have a character count of 4, and the fourth character will be "e", not e':
var word = "cafe"print("total chars in \(word) is \(word.count)")
It prints "total chars in cafe is 4":
word += "\u{301}" // COMBINING ACUTE ACCENT, U+0301print("totalchars in \(word) ...
