Merge pull request #4230 from natecook1000/swift-3.0-branch

[swift-3.0-branch] [stdlib] Revise stdlib documentation comments

Author: tkremenek

stdlib/public/core/Algorithm.swift

@@ -10,9 +10,12 @@
 //
 //===----------------------------------------------------------------------===//
 
-/// Returns the lesser of `x` and `y`.
+/// Returns the lesser of two comparable values.
 ///
-/// If `x == y`, returns `x`.
+/// - Parameters:
+///   - x: A value to compare.
+///   - y: Another value to compare.
+/// - Returns: The lesser of `x` and `y`. If `x` is equal to `y`, returns `x`.
 public func min<T : Comparable>(_ x: T, _ y: T) -> T {
   // In case `x == y` we pick `x`.
   // This preserves any pre-existing order in case `T` has identity,
@@ -23,7 +26,13 @@ public func min<T : Comparable>(_ x: T, _ y: T) -> T {
 
 /// Returns the least argument passed.
 ///
-/// If there are multiple equal least arguments, returns the first one.
+/// - Parameters:
+///   - x: A value to compare.
+///   - y: Another value to compare.
+///   - z: A third value to compare.
+///   - rest: Zero or more additional values.
+/// - Returns: The least of all the arguments. If there are multiple equal
+///   least arguments, the result is the first one.
 public func min<T : Comparable>(_ x: T, _ y: T, _ z: T, _ rest: T...) -> T {
   var minValue = min(min(x, y), z)
   // In case `value == minValue`, we pick `minValue`. See min(_:_:).
@@ -33,17 +42,26 @@ public func min<T : Comparable>(_ x: T, _ y: T, _ z: T, _ rest: T...) -> T {
   return minValue
 }
 
-/// Returns the greater of `x` and `y`.
+/// Returns the greater of two comparable values.
 ///
-/// If `x == y`, returns `y`.
+/// - Parameters:
+///   - x: A value to compare.
+///   - y: Another value to compare.
+/// - Returns: The greater of `x` and `y`. If `x` is equal to `y`, returns `y`.
 public func max<T : Comparable>(_ x: T, _ y: T) -> T {
   // In case `x == y`, we pick `y`. See min(_:_:).
   return y >= x ? y : x
 }
 
 /// Returns the greatest argument passed.
 ///
-/// If there are multiple equal greatest arguments, returns the last one.
+/// - Parameters:
+///   - x: A value to compare.
+///   - y: Another value to compare.
+///   - z: A third value to compare.
+///   - rest: Zero or more additional values.
+/// - Returns: The greatest of all the arguments. If there are multiple equal
+///   greatest arguments, the result is the last one.
 public func max<T : Comparable>(_ x: T, _ y: T, _ z: T, _ rest: T...) -> T {
   var maxValue = max(max(x, y), z)
   // In case `value == maxValue`, we pick `value`. See min(_:_:).
@@ -53,18 +71,20 @@ public func max<T : Comparable>(_ x: T, _ y: T, _ z: T, _ rest: T...) -> T {
   return maxValue
 }
 
-/// The iterator for `EnumeratedSequence`.  `EnumeratedIterator`
-/// wraps a `Base` iterator and yields successive `Int` values,
-/// starting at zero, along with the elements of the underlying
-/// `Base`:
+/// The iterator for `EnumeratedSequence`.
+///
+/// An instance of `EnumeratedIterator` wraps a base iterator and yields
+/// successive `Int` values, starting at zero, along with the elements of the
+/// underlying base iterator. The following example enumerates the elements of
+/// an array:
 ///
 ///     var iterator = ["foo", "bar"].enumerated().makeIterator()
 ///     iterator.next() // (0, "foo")
 ///     iterator.next() // (1, "bar")
 ///     iterator.next() // nil
 ///
-/// - Note: Idiomatic usage is to call `enumerate` instead of
-///   constructing an `EnumerateIterator` directly.
+/// To create an instance of `EnumeratedIterator`, call
+/// `enumerated().makeIterator()` on a sequence or collection.
 public struct EnumeratedIterator<
   Base : IteratorProtocol
 > : IteratorProtocol, Sequence {
@@ -91,14 +111,22 @@ public struct EnumeratedIterator<
   }
 }
 
-/// The type of the `enumerated()` property.
+/// An enumeration of the elements of a sequence or collection.
+///
+/// `EnumeratedSequence` is a sequence of pairs (*n*, *x*), where *n*s are
+/// consecutive `Int` values starting at zero, and *x*s are the elements of a
+/// base sequence.
 ///
-/// `EnumeratedSequence` is a sequence of pairs (*n*, *x*), where *n*s
-/// are consecutive `Int`s starting at zero, and *x*s are the elements
-/// of a `Base` `Sequence`:
+/// To create an instance of `EnumeratedSequence`, call `enumerated()` on a
+/// sequence or collection. The following example enumerates the elements of
+/// an array.
 ///
 ///     var s = ["foo", "bar"].enumerated()
-///     Array(s) // [(0, "foo"), (1, "bar")]
+///     for (n, x) in s {
+///         print("\(n): \(x)")
+///     }
+///     // Prints "0: foo"
+///     // Prints "1: bar"
 public struct EnumeratedSequence<Base : Sequence> : Sequence {
   internal var _base: Base
 
@@ -108,8 +136,6 @@ public struct EnumeratedSequence<Base : Sequence> : Sequence {
   }
 
   /// Returns an iterator over the elements of this sequence.
-  ///
-  /// - Complexity: O(1).
   public func makeIterator() -> EnumeratedIterator<Base.Iterator> {
     return EnumeratedIterator(_base: _base.makeIterator())
   }

stdlib/public/core/AnyHashable.swift

@@ -87,14 +87,14 @@ internal struct _ConcreteHashableBox<Base : Hashable> : _AnyHashableBox {
 
 /// A type-erased hashable value.
 ///
-/// Forwards equality comparisons and hashing operations to an
-/// underlying hashable value, hiding its specific type.
+/// The `AnyHashable` type forwards equality comparisons and hashing operations
+/// to an underlying hashable value, hiding its specific underlying type.
 ///
-/// You can store mixed-type keys in `Dictionary` and other
-/// collections that require `Hashable` by wrapping mixed-type keys in
+/// You can store mixed-type keys in dictionaries and other collections that
+/// require `Hashable` conformance by wrapping mixed-type keys in
 /// `AnyHashable` instances:
 ///
-///     let descriptions: [AnyHashable : Any] = [
+///     let descriptions: [AnyHashable: Any] = [
 ///         AnyHashable("😄"): "emoji",
 ///         AnyHashable(42): "an Int",
 ///         AnyHashable(Int8(43)): "an Int8",
@@ -107,17 +107,24 @@ internal struct _ConcreteHashableBox<Base : Hashable> : _AnyHashableBox {
 public struct AnyHashable {
   internal var _box: _AnyHashableBox
 
-  /// Creates an opaque hashable value that wraps `base`.
+  /// Creates a type-erased hashable value that wraps the given instance.
   ///
-  /// Example:
+  /// The following example creates two type-erased hashable values: `x` wraps
+  /// an `Int` with the value 42, while `y` wraps a `UInt8` with the same
+  /// numeric value. Because the underlying types of `x` and `y` are
+  /// different, the two variables do not compare as equal despite having
+  /// equal underlying values.
   ///
   ///     let x = AnyHashable(Int(42))
   ///     let y = AnyHashable(UInt8(42))
   ///
-  ///     print(x == y) // Prints "false" because `Int` and `UInt8`
-  ///                   // are different types.
+  ///     print(x == y)
+  ///     // Prints "false" because `Int` and `UInt8` are different types
   ///
-  ///     print(x == AnyHashable(Int(42))) // Prints "true".
+  ///     print(x == AnyHashable(Int(42)))
+  ///     // Prints "true"
+  ///
+  /// - Parameter base: A hashable value to wrap.
   public init<H : Hashable>(_ base: H) {
     if let customRepresentation =
       (base as? _HasCustomAnyHashableRepresentation)?._toCustomAnyHashable() {
@@ -135,11 +142,16 @@ public struct AnyHashable {
     self._box = _ConcreteHashableBox(base)
   }
 
-  /// The value wrapped in this `AnyHashable` instance.
+  /// The value wrapped by this instance.
+  ///
+  /// The `base` property can be cast back to its original type using one of
+  /// the casting operators (`as?`, `as!`, or `as`).
   ///
-  ///     let anyMessage = AnyHashable("Hello")
-  ///     let unwrappedMessage: Any = anyMessage.base
-  ///     print(unwrappedMessage) // prints "hello"
+  ///     let anyMessage = AnyHashable("Hello world!")
+  ///     if let unwrappedMessage = anyMessage.base as? String {
+  ///         print(unwrappedMessage)
+  ///     }
+  ///     // Prints "Hello world!"
   public var base: Any {
     return _box._base
   }
@@ -155,6 +167,31 @@ public struct AnyHashable {
 }
 
 extension AnyHashable : Equatable {
+  /// Returns a Boolean value indicating whether two type-erased hashable
+  /// instances wrap the same type and value.
+  ///
+  /// Two instances of `AnyHashable` compare as equal if and only if the
+  /// underlying types have the same conformance to the `Equatable` protocol
+  /// and the underlying values compare as equal.
+  ///
+  /// The following example creates two type-erased hashable values: `x` wraps
+  /// an `Int` with the value 42, while `y` wraps a `UInt8` with the same
+  /// numeric value. Because the underlying types of `x` and `y` are
+  /// different, the two variables do not compare as equal despite having
+  /// equal underlying values.
+  ///
+  ///     let x = AnyHashable(Int(42))
+  ///     let y = AnyHashable(UInt8(42))
+  ///
+  ///     print(x == y)
+  ///     // Prints "false" because `Int` and `UInt8` are different types
+  ///
+  ///     print(x == AnyHashable(Int(42)))
+  ///     // Prints "true"
+  ///
+  /// - Parameters:
+  ///   - lhs: A type-erased hashable value.
+  ///   - rhs: Another type-erased hashable value.
   public static func == (lhs: AnyHashable, rhs: AnyHashable) -> Bool {
     return lhs._box._isEqual(to: rhs._box)
   }