Test: start implementing List

Author: kavon

test/Inputs/Swiftskell.swift

@@ -8,6 +8,11 @@ public protocol Show: ~Copyable {
   borrowing func show() -> String
 }
 
+extension CustomStringConvertible {
+  public func show() -> String { return description }
+}
+extension Int: Show {}
+
 public func print(_ s: borrowing some Show & ~Copyable) {
   print(s.show())
 }
@@ -54,66 +59,48 @@ public protocol Generator: ~Copyable {
 public enum Pair<L: ~Copyable, R: ~Copyable>: ~Copyable {
   case elms(L, R)
 }
+extension Pair: Copyable where L: Copyable, R: Copyable {}
 
 /// MARK: Data.Maybe
+public typealias Maybe<Wrapped: ~Copyable> = Optional<Wrapped>
 
-public enum Maybe<Value: ~Copyable>: ~Copyable {
-  case just(Value)
-  case nothing
-}
-
-extension Maybe: Copyable {}
-
-extension Maybe: Show where Value: Show & ~Copyable {
+extension Maybe: Show where Wrapped: Show & ~Copyable {
   public borrowing func show() -> String {
     switch self {
-      case let .just(elm):
+      case let .some(elm):
         return elm.show()
-      case .nothing:
+      case .none:
         return "<nothing>"
     }
   }
 }
 
-extension Maybe: Eq where Value: Eq, Value: ~Copyable {
+extension Maybe: Eq where Wrapped: Eq, Wrapped: ~Copyable {
   public static func ==(_ a: borrowing Self, _ b: borrowing Self) -> Bool {
     switch a {
-      case let .just(a1):
+      case let .some(a1):
         switch b {
-          case let .just(b1):
+          case let .some(b1):
             return a1 == b1
-          case .nothing:
+          case .none:
             return false
         }
-      case .nothing:
+      case .none:
         switch b {
-          case .just:
+          case .some:
             return false
-          case .nothing:
+          case .none:
             return true
         }
     }
   }
 }
 
-
-// FIXME: triggers crash!
-// @inlinable
-// public func fromMaybe<A: ~Copyable>(_ defaultVal: consuming A, 
-//                                     _ mayb: consuming Maybe<A>) -> A {
-//   switch mayb {
-//     case let .just(payload):
-//       return payload
-//     case .nothing:
-//       return defaultVal
-//   }
-// }
-
 public func isJust<A: ~Copyable>(_ m: borrowing Maybe<A>) -> Bool {
   switch m {
-    case .just:
+    case .some:
       return true
-    case .nothing:
+    case .none:
       return false
   }
 }
@@ -127,3 +114,144 @@ public struct UnownedRef<Instance: AnyObject> {
   @usableFromInline
   internal unowned(unsafe) var _value: Instance
 }
+
+/// Provides underlying support so that you can create recursive enums, because
+/// noncopyable enums do not yet support indirect cases.
+public struct Box<Wrapped: ~Copyable>: ~Copyable {
+  private let _pointer: UnsafeMutablePointer<Wrapped>
+
+  init(_ wrapped: consuming Wrapped) {
+    _pointer = .allocate(capacity: 1)
+    _pointer.initialize(to: wrapped)
+  }
+
+  deinit {
+    _pointer.deinitialize(count: 1)
+    _pointer.deallocate()
+  }
+
+  consuming func take() -> Wrapped {
+    let wrapped = _pointer.move()
+    _pointer.deallocate()
+    discard self
+    return wrapped
+  }
+
+  var borrow: Wrapped {
+    _read { yield _pointer.pointee }
+  }
+
+  consuming func map(_ transform: (consuming Wrapped) -> Wrapped) -> Self {
+    _pointer.initialize(to: transform(_pointer.move()))
+    return self
+  }
+}
+
+
+/// MARK: Data.List
+public enum List<Element: ~Copyable>: ~Copyable {
+  case cons(Element, Box<List<Element>>)
+  case empty
+
+  public init(_ head: consuming Element,
+              _ tail: consuming List<Element>) {
+    self = .cons(head, Box(tail))
+  }
+
+  public init() { self = .empty }
+}
+
+/// Pure Iteration
+extension List where Element: ~Copyable {
+  /// Performs forward iteration through the list, accumulating a result value.
+  /// Returns f(xn,...,f(x2, f(x1, init))...), or init if the list is empty.
+  public borrowing func foldl<Out>(
+                        init initial: consuming Out,
+                        _ f: (borrowing Element, consuming Out) -> Out) -> Out
+                        where Out: ~Copyable {
+    func loop(_ acc: consuming Out, _ lst: borrowing Self) -> Out {
+      switch lst {
+        case .empty:
+            return acc
+        case let .cons(elm, tail):
+          return loop(f(elm, acc), tail.borrow)
+      }
+    }
+    return loop(initial, self)
+  }
+
+  /// Performs reverse iteration through the list, accumulating a result value.
+  /// Returns f(x1, f(x2,...,f(xn, init)...)) or init if the list is empty.
+  public borrowing func foldr<Out>(
+                        init initial: consuming Out,
+                        _ f: (borrowing Element, consuming Out) -> Out) -> Out
+                        where Out: ~Copyable {
+  switch self {
+    case .empty:
+      return initial
+    case let .cons(elm, tail):
+      return f(elm, tail.borrow.foldr(init: initial, f))
+    }
+  }
+
+  // Forward iteration without accumulating a result.
+  public borrowing func forEach(_ f: (borrowing Element) -> Void) -> Void {
+    switch self {
+    case .empty: return
+    case let .cons(elm, tail):
+      f(elm)
+      return tail.borrow.forEach(f)
+    }
+  }
+}
+
+/// Initialization
+extension List where Element: ~Copyable {
+  // Generates a list of elements [f(0), f(1), ..., f(n-1)] from left to right.
+  // For n < 0, the empty list is created.
+  public init(length n: Int, _ f: (Int) -> Element) {
+    guard n > 0 else {
+      self = .empty
+      return
+    }
+
+    let cur = n-1
+    let elm = f(cur)
+    self = List(elm, List(length: cur, f))
+  }
+}
+
+/// Basic utilities
+extension List where Element: ~Copyable {
+  /// Is this list empty?
+  public borrowing func empty() -> Bool {
+    switch self {
+    case .empty: return true
+    case .cons(_, _): return false
+    }
+  }
+
+  /// How many elements are in this list?
+  public borrowing func length() -> Int {
+    return foldl(init: 0) { $1 + 1 }
+  }
+
+  /// Pop the first element off the list, if present.
+  public consuming func pop() -> Maybe<Pair<Element, List<Element>>> {
+    switch consume self {
+      case .empty: .none
+      case let .cons(elm, tail): .elms(elm, tail.take())
+    }
+  }
+
+  /// Push an element onto the list.
+  public consuming func push(_ newHead: consuming Element) -> List<Element> {
+    return List(newHead, self)
+  }
+}
+
+extension List: Show where Element: Show & ~Copyable {
+  public borrowing func show() -> String {
+    return "[" + foldl(init: "]", { $0.show() + ", " + $1 })
+  }
+}

test/Interpreter/moveonly_swiftskell.swift

@@ -1,22 +1,64 @@
 // RUN: %empty-directory(%t)
 
-// RUN: %target-build-swift \
+// RUN: %target-build-swift-dylib(%t/%target-library-name(Swiftskell)) \
+// RUN:    -module-name Swiftskell \
 // RUN:    -emit-module      \
-// RUN:    -emit-module-path %t \
+// RUN:    -emit-module-path %t/Swiftskell.swiftmodule \
 // RUN:    -enable-library-evolution \
-// RUN:    -module-name Swiftskell \
 // RUN:    -parse-as-library \
 // RUN:    %S/../Inputs/Swiftskell.swift \
 // RUN:   -enable-experimental-feature SuppressedAssociatedTypes \
 // RUN:   -enable-experimental-feature NonescapableTypes
 
-// RUN: %target-build-swift %s -I %t -o %t/a.out
-// RUN: %target-codesign %t/a.out
-// RUN: %target-run %t/a.out | %FileCheck %s
+// RUN: %target-build-swift -I%t -L%t -lSwiftskell -parse-as-library %s \
+// RUN:                     -module-name E -o %t/E %target-rpath(%t)
+// RUN: %target-codesign %t/E
+// RUN: %target-codesign %t/%target-library-name(Swiftskell)
+// RUN: %target-run %t/E %t/%target-library-name(Swiftskell) | %FileCheck %s
 
 // REQUIRES: executable_test
 
 import Swiftskell
 
-print("hello, world")
-// CHECK: hello, world
+/// assertion function
+func check(_ result: Bool, _ string: String? = nil, _ line: Int = #line) {
+  if result { return }
+  var msg = "assertion failure (line \(line))"
+  if let extra = string {
+    msg += ":\t" + extra
+  }
+  fatalError(msg)
+}
+
+/// Basic noncopyable type for testing.
+struct File: ~Copyable, Show {
+  let id: Int
+  init(_ id: Int) {
+    self.id = id
+  }
+  func show() -> String { return id.show() }
+}
+
+
+@main
+struct Main {
+  static func main() {
+    testListBasic()
+  }
+}
+
+func testListBasic() {
+  var items = List<File>(length: 5) { .init($0) }
+  print(items.show())  // CHECK: [0, 1, 2, 3, 4, ]
+  check(items.length() == 5)
+  check(!items.empty())
+
+  items = .empty
+  check(items.length() == 0)
+  check(items.empty())
+
+  let nums = List<Int>().push(7).push(7).push(3)
+  print(nums.show()) // CHECK: [7, 7, 3, ]
+
+  
+}