-> Lexer.Result { switch self.peek() { case UInt8(ascii: "0"), UInt8(ascii: "1"), UInt8(ascii: "2"), UInt8(ascii: "3"), UInt8(ascii: "4"), UInt8(ascii: "5"), UInt8(ascii: "6"), UInt8(ascii: "7"), UInt8(ascii: "8"), UInt8(ascii: "9"): return self.lexNumber() ... } ... } 24 — Quick Overview of SwiftParser, Yusuke Kita (@kitasuke)