As List/Array

Author: CodaFi

Swiftz/ArrayExt.swift

@@ -8,6 +8,52 @@
 
 /// MARK: Array extensions
 
+public enum ArrayMatcher<A> {
+	case Nil
+	case Cons(A, [A])
+}
+
+/// Destructures a list into its constituent parts.
+///
+/// If the given list is empty, this function returns .Empty.  If the list is non-empty, this
+/// function returns .Cons(hd, tl)
+public func match<T>(l : [T]) -> ArrayMatcher<T> {
+	if l.count == 0 {
+		return .Nil
+	} else if l.count == 1 {
+		return .Cons(l[0], [])
+	}
+	let hd = l[0]
+	let tl = Array<T>(l[1..<l.count])
+	return .Cons(hd, tl)
+}
+
+/// Returns the first element in the list, or None if the list is empty.
+public func head<A>(l : [A]) -> Optional<A> {
+	switch match(l) {
+	case .Nil:
+		return .None
+	case .Cons(let x, _):
+		return .Some(x)
+	}
+}
+
+/// Returns the tail of the list, or None if the list is empty.
+public func tail<A>(l : [A]) -> Optional<[A]> {
+	switch match(l) {
+	case .Nil:
+		return .None
+	case .Cons(_, let xs):
+		return .Some(xs)
+	}
+}
+
+/// Adds an element to the front of a list.
+public func cons<T>(lhs : T, var rhs : [T]) -> [T] {
+	rhs.insert(lhs, atIndex: 0)
+	return rhs
+}
+
 /// Safely indexes into an array by converting out of bounds errors to nils.
 public func safeIndex<T>(array : Array<T>)(i : Int) -> T? {
 	return indexArray(array, i)

Swiftz/Set.swift

@@ -190,6 +190,16 @@ public struct Set<A : Hashable> {
 	public func reduce<B>(f : (B, A) -> B, initial : B) -> B {
 		return array.reduce(initial, combine: f)
 	}
+	
+	/// Returns all elements of the receiver in a List in no particular order.
+	public func toList() -> List<A> {
+		return self.reduce(flip(List.cons), initial: List())
+	}
+	
+	/// Returns all elements of the receiver in an Array in no particular order.
+	public func toArray() -> Array<A> {
+		return self.reduce(flip(cons), initial: [])
+	}
 }
 
 extension Set : ArrayLiteralConvertible {