Remove Term.Empty.

prototype/Doubt/Diff.swift

@@ -4,17 +4,15 @@ public enum Diff: Comparable, CustomDebugStringConvertible, CustomDocConvertible
 	indirect case Copy(Syntax<Diff>)
 
 	public static func Insert(term: Term) -> Diff {
-		return .Patch(.Empty, term)
+		return .Patch(Term(.Empty), term)
 	}
 
 	public static func Delete(term: Term) -> Diff {
-		return .Patch(term, .Empty)
+		return .Patch(term, Term(.Empty))
 	}
 
 	public init(_ term: Term) {
 		switch term {
-		case .Empty:
-			self = .Empty
 		case let .Roll(s):
 			self = .Copy(s.map(Diff.init))
 		}
@@ -55,12 +53,7 @@ public enum Diff: Comparable, CustomDebugStringConvertible, CustomDocConvertible
 	}
 
 	public init(_ a: Term, _ b: Term) {
-		switch (a, b) {
-		case (.Empty, .Empty):
-			self = .Empty
-
-		case let (.Roll(a), .Roll(b)):
-			switch (a, b) {
+		switch (a.syntax, b.syntax) {
 		case let (.Apply(a, aa), .Apply(b, bb)):
 			self = .Copy(.Apply(Diff(a, b), Diff.diff(aa, bb)))
 
@@ -80,11 +73,7 @@ public enum Diff: Comparable, CustomDebugStringConvertible, CustomDocConvertible
 			self = .Copy(.Group(Diff(n1, n2), Diff.diff(v1, v2)))
 
 		default:
-				self = .Patch(Term(a), Term(b))
-			}
-
-		default:
-			self = Patch(a, b)
+			self = .Patch(a, b)
 		}
 	}
 

prototype/Doubt/Equatable.swift

@@ -1,13 +1,5 @@
 public func == (left: Term, right: Term) -> Bool {
-	switch (left, right) {
-	case (.Empty, .Empty):
-		return true
-	case let (.Roll(s), .Roll(t)):
-		return s == t
-
-	default:
-		return false
-	}
+	return left.syntax == right.syntax
 }
 
 public func == <F: Equatable> (left: Syntax<F>, right: Syntax<F>) -> Bool {

prototype/Doubt/Syntax.swift

@@ -3,13 +3,17 @@ public enum Term: CustomDebugStringConvertible, CustomDocConvertible, CustomStri
 		self = .Roll(out)
 	}
 
-	case Empty
 	indirect case Roll(Syntax<Term>)
 
+	public var syntax: Syntax<Term> {
+		switch self {
+		case let .Roll(syntax):
+			return syntax
+		}
+	}
+
 	public var debugDescription: String {
 		switch self {
-		case .Empty:
-			return ".Empty"
 		case let .Roll(s):
 			return s.debugDescription
 		}
@@ -17,8 +21,6 @@ public enum Term: CustomDebugStringConvertible, CustomDocConvertible, CustomStri
 
 	public var doc: Doc {
 		switch self {
-		case .Empty:
-			return .Empty
 		case let .Roll(s):
 			return s.doc
 		}