Swift4.2Released!--Sequence method
・last(where:), lastIndex(where:), lastIndex(of:)が追加
・ index(of:) とindex(where:) が firstIndex(of:) とfirstIndex(where:)にメソッド名が変更
・RangeReplaceableCollection プロトコルに removeAll(where:) が追加
last(where:), lastIndex(where:), lastIndex(of:)については最