swift-mirror/stdlib/public/core/SequenceAlgorithms.swift.gyb

//===--- SequenceAlgorithms.swift.gyb -------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See http://swift.org/LICENSE.txt for license information
// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

%{

# We know we will eventually get a SequenceType.Element type.  Define
# a shorthand that we can use today.
GElement = "Generator.Element"

}%

//===----------------------------------------------------------------------===//
// enumerate()
//===----------------------------------------------------------------------===//

extension SequenceType {
  /// Return a lazy `SequenceType` containing pairs (*n*, *x*), where
  /// *n*\ s are consecutive `Int`\ s starting at zero, and *x*\ s are
  /// the elements of `base`::
  ///
  ///   > for (n, c) in enumerate("Swift") { println("\(n): '\(c)'" ) }
  ///   0: 'S'
  ///   1: 'w'
  ///   2: 'i'
  ///   3: 'f'
  ///   4: 't'
  final public func _prext_enumerate() -> EnumerateSequence<Self> {
    return EnumerateSequence(self)
  }
}

//===----------------------------------------------------------------------===//
// minElement(), maxElement()
//===----------------------------------------------------------------------===//

% # Generate two versions: with explicit predicates and with
% # a Comparable requirement.
% for preds in [ True, False ]:

extension SequenceType ${"" if preds else "where Self.Generator.Element : Comparable"} {

  /// Returns the minimum element in `self`.
  ///
  /// Complexity: O(count(elements))
%   if preds:
  ///
  /// Requires: `isOrderedBefore` is a `strict weak ordering
  /// <http://en.wikipedia.org/wiki/Strict_weak_order#Strict_weak_orderings>`__
  /// over `self`."""
%   end
  final public func _prext_minElement(
%   if preds:
    @noescape isOrderedBefore: (${GElement}, ${GElement}) -> Bool
%   end
  ) -> ${GElement}? {
    var g = generate()
    if var result? = g.next() {
      for e in GeneratorSequence(g) {
%   if preds:
        if isOrderedBefore(e, result) { result = e }
%   else:
        if e < result { result = e }
%   end
      }
      return result
    }
    return nil
  }

  /// Returns the maximum element in `self`.
  ///
  /// Complexity: O(count(elements))
%   if preds:
  ///
  /// Requires: `isOrderedBefore` is a `strict weak ordering
  /// <http://en.wikipedia.org/wiki/Strict_weak_order#Strict_weak_orderings>`__
  /// over `self`."""
%   end
  final public func _prext_maxElement(
%   if preds:
    @noescape isOrderedBefore: (${GElement}, ${GElement}) -> Bool
%   end
  ) -> ${GElement}? {
    var g = generate()
    if var result? = g.next() {
      for e in GeneratorSequence(g) {
%   if preds:
        if isOrderedBefore(result, e) { result = e }
%   else:
        if e > result { result = e }
%   end
      }
      return result
    }
    return nil
  }
}

% end

//===----------------------------------------------------------------------===//
// startsWith()
//===----------------------------------------------------------------------===//

% # Generate two versions: with explicit predicates and with
% # an Equatable requirement.
% for preds in [ True, False ]:

extension SequenceType ${"" if preds else "where Self.Generator.Element : Equatable"} {

%   if preds:
  /// Return true iff `s` begins with elements equivalent to those of
  /// `prefix`, using `isEquivalent` as the equivalence test.
  ///
  /// Requires: `isEquivalent` is an `equivalence relation
  /// <http://en.wikipedia.org/wiki/Equivalence_relation>`_
%   else:
  /// Return true iff the the initial elements of `s` are equal to `prefix`.
%   end
  final public func _prext_startsWith<
    S : SequenceType where S.${GElement} == ${GElement}
  >(
    prefix: S${"," if preds else ""}
%   if preds:
    @noescape isEquivalent: (${GElement}, ${GElement}) -> Bool
%   end
    ) -> Bool {
    var prefixGenerator = prefix.generate()
    for e0 in self {
      if let e1? = prefixGenerator.next() {
        if ${"!isEquivalent(e0, e1)" if preds else "e0 != e1"} {
          return false
        }
      }
      else {
        return true
      }
    }
    return prefixGenerator.next() != nil ? false : true
  }
}

% end

//===----------------------------------------------------------------------===//
// equalElements()
//===----------------------------------------------------------------------===//

% # Generate two versions: with explicit predicates and with
% # an Equatable requirement.
% for preds in [ True, False ]:

extension SequenceType ${"" if preds else "where Self.Generator.Element : Equatable"} {

%   if preds:
  /// Return true iff `a1` and `a2` contain equivalent elements, using
  /// `isEquivalent` as the equivalence test.
  ///
  /// Requires: `isEquivalent` is an `equivalence relation
  /// <http://en.wikipedia.org/wiki/Equivalence_relation>`_
%   else:
  /// Return `true` iff `self` and `s` contain the same elements in the
  /// same order.
%   end
  final public func _prext_equalElements<
    S : SequenceType where S.${GElement} == ${GElement}
  >(
    s: S${"," if preds else ""}
%   if preds:
    @noescape isEquivalent: (${GElement}, ${GElement}) -> Bool
%   end
  ) -> Bool {
    var g1 = self.generate()
    var g2 = s.generate()
    while true {
      switch (g1.next(), g2.next()) {
      case let (e1?, e2?):
%   if preds:
        if !isEquivalent(e1, e2) {
%   else:
        if e1 != e2 {
%   end
          return false
        }
      case (_?, nil),
           (nil, _?):
        return false
      case (nil, nil):
        return true
      }
    }
  }
}

% end

//===----------------------------------------------------------------------===//
// lexicographicalCompare()
//===----------------------------------------------------------------------===//

% # Generate two versions: with explicit predicates and with
% # Comparable requirement.
% for preds in [ True, False ]:

%   if preds:
/// Return true iff `a1` precedes `a2` in a lexicographical ("dictionary")
/// ordering, using `isOrderedBefore` as the comparison between elements.
///
/// Requires: isOrderedBefore` is a `strict weak ordering
/// <http://en.wikipedia.org/wiki/Strict_weak_order#Strict_weak_orderings>`__
/// over the elements of `a1` and `a2`.
%   else:
/// Return true iff a1 precedes a2 in a lexicographical ("dictionary")
/// ordering, using "<" as the comparison between elements.
%   end
extension SequenceType ${"" if preds else "where Self.Generator.Element : Comparable"} {
  final public func _prext_lexicographicalCompare<
    S : SequenceType where S.${GElement} == ${GElement}
  >(
    s: S${"," if preds else ""}
%   if preds:
    @noescape isOrderedBefore less: (${GElement}, ${GElement}) -> Bool
%   end
  ) -> Bool {
    var g1 = self.generate()
    var g2 = s.generate()
    while true {
      if let e1? = g1.next() {
        if let e2? = g2.next() {
          if ${"less(e1, e2)" if preds else "e1 < e2"} {
            return true
          }
          if ${"less(e2, e1)" if preds else "e2 < e1"} {
            return false
          }
          continue // equivalent
        }
        return false
      }

      return g2.next() != nil
    }
  }
}

% end

//===----------------------------------------------------------------------===//
// contains()
//===----------------------------------------------------------------------===//

extension SequenceType where Self.Generator.Element : Equatable {
  /// Return `true` iff `x` is in `self`.
  final public func _prext_contains(element: ${GElement}) -> Bool {
    if let result? = _customContainsEquatableElement(element) {
      return result
    }

    for e in self {
      if e == element {
        return true
      }
    }
    return false
  }
}

extension SequenceType {
  /// Return `true` iff an element in `self` satisfies `predicate`.
  final public func _prext_contains(
    @noescape predicate: (${GElement}) -> Bool
  ) -> Bool {
    for e in self {
      if predicate(e) {
        return true
      }
    }
    return false
  }
}

//===----------------------------------------------------------------------===//
// reduce()
//===----------------------------------------------------------------------===//

extension SequenceType {
  /// Return the result of repeatedly calling `combine` with an
  /// accumulated value initialized to `initial` and each element of
  /// `self`, in turn, i.e. return
  /// `combine(combine(...combine(combine(initial, self[0]),
  /// self[1]),...self[count-2]), self[count-1])`.
  final public func _prext_reduce<T>(
    initial: T, @noescape combine: (T, ${GElement}) -> T
  ) -> T {
    var result = initial
    for element in self {
      result = combine(result, element)
    }
    return result
  }
}

//===----------------------------------------------------------------------===//
// reverse()
//===----------------------------------------------------------------------===//

extension SequenceType {
  /// Return an `Array` containing the elements of `self` in reverse
  /// order.
  final public func _prext_reverse() -> [${GElement}] {
    // FIXME(performance): optimize to 1 pass?  But Array(self) can be
    // optimized to a memcpy() sometimes.  Those cases are usually collections,
    // though.
    var result = Array(self)
    let count = result.count
    for i in 0..<count/2 {
      swap(&result[i], &result[count - i - 1])
    }
    return result
  }
}

extension CollectionType where Self.Index : BidirectionalIndexType {
  /// Return a lazy `CollectionType` containing the elements of `self`
  /// in reverse order.
  final public func _prext_reverse() -> BidirectionalReverseView<Self> {
    return BidirectionalReverseView(self)
  }
}

extension CollectionType where Self.Index : RandomAccessIndexType {
  /// Return a lazy `CollectionType` containing the elements of `self`
  /// in reverse order.
  final public func _prext_reverse() -> RandomAccessReverseView<Self> {
    return RandomAccessReverseView(self)
  }
}

//===----------------------------------------------------------------------===//
// filter()
//===----------------------------------------------------------------------===//

// We would like to make filter() a protocol requirement, and dynamically
// dispatched, but Swift generics don't allow us to express this.
// rdar://20477576

extension SequenceType {
  /// Return an `Array` containing the elements of `self`,
  /// in order, that satisfy the predicate `includeElement`.
  final public func _prext_filter(
    @noescape includeElement: (${GElement}) -> Bool
  ) -> [${GElement}] {
    // Cast away @noescape.
    typealias IncludeElement = (${GElement}) -> Bool
    let escapableIncludeElement =
      unsafeBitCast(includeElement, IncludeElement.self)
    return Array<${GElement}>(lazy(self).filter(escapableIncludeElement))
  }
}

//===----------------------------------------------------------------------===//
// map()
//===----------------------------------------------------------------------===//

extension SequenceType {
  /// Return an `Array` containing the results of mapping `transform`
  /// over `self`.
  final public func _prext_map<T>(
    @noescape transform: (${GElement}) -> T
  ) -> [T] {
    // Cast away @noescape.
    typealias Transform = (${GElement}) -> T
    let escapableTransform = unsafeBitCast(transform, Transform.self)
    return Array<T>(lazy(self).map(escapableTransform))
  }
}

//===----------------------------------------------------------------------===//
// flatMap()
//===----------------------------------------------------------------------===//

extension SequenceType {
  /// Return an `Array` containing the results of mapping `transform`
  /// over `self` and flattening the result.
  final public func _prext_flatMap<S : SequenceType>(
    @noescape transform: (${GElement}) -> S
  ) -> [S.${GElement}] {
    var result: [S.${GElement}] = []
    for element in self {
      result.extend(transform(element))
    }
    return result
  }
}

extension SequenceType {
  /// Return an `Array` containing the non-nil results of mapping `transform`
  /// over `self`.
  final public func _prext_flatMap<T>(
    @noescape transform: (${GElement}) -> T?
  ) -> [T] {
    var result: [T] = []
    for element in self {
      if let newElement? = transform(element) {
        result.append(newElement)
      }
    }
    return result
  }
}

//===----------------------------------------------------------------------===//
// zip()
//===----------------------------------------------------------------------===//

extension SequenceType {
  /// Returns a sequence of pairs built out of two underlying sequences,
  /// where the elements of the `i`\ th pair are the `i`\ th elements
  /// of each underlying sequence.
  final public func _prext_zip<S : SequenceType>(s: S) -> Zip2<Self, S> {
    return Zip2(self, s)
  }
}

// FIXME: we could have an overload on collections that returns a collection
// and preserves the index kind.  Zip2 is only a sequence.