Merge pull request #38 from open-swift/hd/json

RFC 7159 JSON Using Internal Number

Sources/JSON.swift

@@ -0,0 +1,50 @@
+public enum JSON {
+    public enum Number {
+        case integer(Int)
+        case unsignedInteger(UInt)
+        case double(Double)
+    }
+    case object([String: JSON])
+    case array([JSON])
+    case number(JSON.Number)
+    case string(String)
+    case boolean(Bool)
+    case null
+}
+
+//
+// TODO: refactor with
+// https://github.com/apple/swift-evolution/blob/master/proposals/0080-failable-numeric-initializers.md
+//
+
+extension Int {
+    public init?(_ number: JSON.Number) {
+        switch number {
+        case let .integer(value)                                         : self.init(value)
+        case let .unsignedInteger(value) where value <= UInt(Int.max)    : self.init(value)
+        case let .double(value)          where value <= Double(Int32.max): self.init(value)
+        default: return nil
+        }
+    }
+}
+
+extension UInt {
+    public init?(_ number: JSON.Number) {
+        switch number {
+        case let .integer(value)         where value > 0                  : self.init(value)
+        case let .unsignedInteger(value)                                  : self.init(value)
+        case let .double(value)          where value <= Double(UInt32.max): self.init(value)
+        default: return nil
+        }
+    }
+}
+
+extension Double {
+    public init(_ number: JSON.Number) {
+        switch number {
+        case let .integer(value)        : self.init(value)
+        case let .unsignedInteger(value): self.init(value)
+        case let .double(value)         : self.init(value)
+        }
+    }
+}