| //===--- FlatMap.swift ----------------------------------------------------===// |
| // |
| // This source file is part of the Swift.org open source project |
| // |
| // Copyright (c) 2014 - 2016 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 |
| // |
| //===----------------------------------------------------------------------===// |
| |
| extension LazySequenceProtocol { |
| /// Returns the concatenated results of mapping `transform` over |
| /// `self`. Equivalent to |
| /// |
| /// self.map(transform).joined() |
| /// |
| /// - Complexity: O(1) |
| public func flatMap<SegmentOfResult : Sequence>( |
| _ transform: @escaping (Elements.Iterator.Element) -> SegmentOfResult |
| ) -> LazySequence< |
| FlattenSequence<LazyMapSequence<Elements, SegmentOfResult>>> { |
| return self.map(transform).joined() |
| } |
| |
| /// Returns a `LazyMapSequence` containing the concatenated non-nil |
| /// results of mapping transform over this `Sequence`. |
| /// |
| /// Use this method to receive only nonoptional values when your |
| /// transformation produces an optional value. |
| /// |
| /// - Parameter transform: A closure that accepts an element of this |
| /// sequence as its argument and returns an optional value. |
| public func flatMap<ElementOfResult>( |
| _ transform: @escaping (Elements.Iterator.Element) -> ElementOfResult? |
| ) -> LazyMapSequence< |
| LazyFilterSequence< |
| LazyMapSequence<Elements, ElementOfResult?>>, |
| ElementOfResult |
| > { |
| return self.map(transform).filter { $0 != nil }.map { $0! } |
| } |
| } |
| |
| extension LazyCollectionProtocol { |
| /// Returns the concatenated results of mapping `transform` over |
| /// `self`. Equivalent to |
| /// |
| /// self.map(transform).joined() |
| /// |
| /// - Complexity: O(1) |
| public func flatMap<SegmentOfResult : Collection>( |
| _ transform: @escaping (Elements.Iterator.Element) -> SegmentOfResult |
| ) -> LazyCollection< |
| FlattenCollection< |
| LazyMapCollection<Elements, SegmentOfResult>> |
| > { |
| return self.map(transform).joined() |
| } |
| |
| /// Returns a `LazyMapCollection` containing the concatenated non-nil |
| /// results of mapping transform over this collection. |
| /// |
| /// Use this method to receive only nonoptional values when your |
| /// transformation produces an optional value. |
| /// |
| /// - Parameter transform: A closure that accepts an element of this |
| /// collection as its argument and returns an optional value. |
| public func flatMap<ElementOfResult>( |
| _ transform: @escaping (Elements.Iterator.Element) -> ElementOfResult? |
| ) -> LazyMapCollection< |
| LazyFilterCollection< |
| LazyMapCollection<Elements, ElementOfResult?>>, |
| ElementOfResult |
| > { |
| return self.map(transform).filter { $0 != nil }.map { $0! } |
| } |
| } |
| |
| extension LazyCollectionProtocol |
| where |
| Self : BidirectionalCollection, |
| Elements : BidirectionalCollection |
| { |
| /// Returns the concatenated results of mapping `transform` over |
| /// `self`. Equivalent to |
| /// |
| /// self.map(transform).joined() |
| /// |
| /// - Complexity: O(1) |
| public func flatMap<SegmentOfResult : Collection>( |
| _ transform: @escaping (Elements.Iterator.Element) -> SegmentOfResult |
| ) -> LazyCollection< |
| FlattenBidirectionalCollection< |
| LazyMapBidirectionalCollection<Elements, SegmentOfResult>>> |
| where SegmentOfResult : BidirectionalCollection { |
| return self.map(transform).joined() |
| } |
| |
| /// Returns a `LazyMapBidirectionalCollection` containing the concatenated non-nil |
| /// results of mapping transform over this collection. |
| /// |
| /// Use this method to receive only nonoptional values when your |
| /// transformation produces an optional value. |
| /// |
| /// - Parameter transform: A closure that accepts an element of this |
| /// collection as its argument and returns an optional value. |
| public func flatMap<ElementOfResult>( |
| _ transform: @escaping (Elements.Iterator.Element) -> ElementOfResult? |
| ) -> LazyMapBidirectionalCollection< |
| LazyFilterBidirectionalCollection< |
| LazyMapBidirectionalCollection<Elements, ElementOfResult?>>, |
| ElementOfResult |
| > { |
| return self.map(transform).filter { $0 != nil }.map { $0! } |
| } |
| } |