Sequence ops

ExSwift.xcodeproj/project.pbxproj

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ExSwift/Sequence.swift

@@ -0,0 +1,242 @@
+//
+//  Sequence.swift
+//  ExSwift
+//
+//  Created by Colin Eberhardt on 24/06/2014.
+//  Copyright (c) 2014 pNre. All rights reserved.
+//
+
+import Foundation
+
+
+extension SequenceOf {
+
+    /**
+    *  First element of the sequence
+    *  @return First element of the sequence if present
+    */
+    func first () -> T? {
+        var generator =  self.generate();
+        return generator.next()
+    }
+
+    /**
+    *  Checks if call returns true for any element of self
+    *  @param call Function to call for each element
+    *  @return True if call returns true for any element of self
+    */
+    func any (call: (T) -> Bool) -> Bool {
+        var generator =  self.generate();
+        while let nextItem = generator.next() {
+            if call(nextItem) {
+                return true
+            }
+        }
+        return false
+    }
+
+    /**
+    *  Object at the specified index if exists
+    *  @param index
+    *  @return Object at index in sequence, nil if index is out of bounds
+    */
+    func get (index: Int) -> T? {
+        var generator =  self.generate();
+        for _ in 0..(index-1) {
+            generator.next()
+        }
+        return generator.next()
+    }
+
+    /**
+    *  Objects in the specified range
+    *  @param range
+    *  @return Subsequence in range
+    */
+    func get (range: Range<Int>) -> SequenceOf<T> {
+        return self.skip(range.startIndex)
+            .take(range.endIndex - range.startIndex)
+    }
+
+    /**
+    *  Index of the first occurrence of item, if found
+    *  @param item The item to search for
+    *  @return Index of the matched item or nil
+    */
+    func indexOf <U: Equatable> (item: U) -> Int? {
+        var index = 0;
+        for current in self {
+            if let equatable = current as? U {
+                if equatable == item {
+                    return index
+                }
+            }
+            index++
+        }
+        return nil
+    }
+
+    /**
+    *  Subsequence from n to the end of the sequence
+    *  @return Sequence from n to the end
+    */
+    func skip (n:Int) -> SequenceOf<T> {
+        var generator =  self.generate();
+        for _ in 0..n {
+            generator.next()
+        }
+        return SequenceOf(generator)
+    }
+
+    /**
+    *  Filters the sequence only including items that match the test
+    *  @param include Function invoked to test elements for inclusion in the sequence
+    *  @return Filtered sequence
+    */
+    func filter(include: (T) -> Bool) -> SequenceOf<T> {
+        return SequenceOf(FilterSequence(self, include))
+    }
+
+    /**
+    *  Opposite of filter
+    *  @param exclude Function invoked to test elements for exlcusion from the sequence
+    *  @return Filtered sequence
+    */
+    func reject (exclude: (T -> Bool)) -> SequenceOf<T> {
+        return self.filter {
+            return !exclude($0)
+        }
+    }
+
+    /**
+    *  Skips the elements in the sequence up until the condition returns false
+    *  @param condition A function which returns a boolean if an element satisfies a given condition or not
+    *  @return Elements of the sequence starting with the element which does not meet the condition
+    */
+    func skipWhile(condition:(T) -> Bool) -> SequenceOf<T> {
+        var generator =  self.generate();
+        var keepSkipping = true
+        while keepSkipping {
+            if let nextItem = generator.next() {
+                keepSkipping = condition(nextItem)
+            } else {
+                keepSkipping = false
+            }
+        }
+        return SequenceOf(generator)
+    }
+
+    /**
+    *  Checks if self contains the item object
+    *  @param item The item to search for
+    *  @return true if self contains item
+    */
+    func contains<T:Equatable> (item: T) -> Bool {
+        var generator =  self.generate();
+        while let nextItem = generator.next() {
+            if nextItem as T == item {
+                return true;
+            }
+        }
+        return false
+    }
+
+    /**
+    *  Returns the first n elements from self
+    *  @return First n elements
+    */
+    func take (n:Int) -> SequenceOf<T> {
+        return SequenceOf(TakeSequence(self, n))
+    }
+
+    /**
+    *  Returns the elements of the sequence up until an element does not meet the condition
+    *  @param condition A function which returns a boolean if an element satisfies a given condition or not.
+    *  @return Elements of the sequence up until an element does not meet the condition
+    */
+    func takeWhile (condition:(T?) -> Bool) -> SequenceOf<T>  {
+        return SequenceOf(TakeWhileSequence(self, condition))
+    }
+}
+
+// a sequence adapter that implements the 'filter' functionality
+struct FilterSequence<S:Sequence>: Sequence {
+    let sequence: S
+    let includeElement: (S.GeneratorType.Element) -> Bool
+
+    init(_ sequence: S, _ includeElement: (S.GeneratorType.Element) -> Bool) {
+        self.sequence = sequence
+        self.includeElement = includeElement
+    }
+
+    func generate() -> GeneratorOf<S.GeneratorType.Element> {
+        var generator = self.sequence.generate()
+        return GeneratorOf<S.GeneratorType.Element> {
+            var keepSkipping = true
+            var nextItem = generator.next()
+            while keepSkipping {
+                if let unwrappedItem = nextItem {
+                    keepSkipping = !self.includeElement(unwrappedItem)
+                } else {
+                    keepSkipping = false
+                }
+
+                if (keepSkipping) {
+                    nextItem = generator.next()
+                }
+            }
+            return nextItem
+        }
+    }
+}
+
+// a sequence adapter that implements the 'take' functionality
+struct TakeSequence<S:Sequence>: Sequence {
+    let sequence: S
+    let n: Int
+
+    init(_ sequence: S, _ n: Int) {
+        self.sequence = sequence
+        self.n = n
+    }
+
+    func generate() -> GeneratorOf<S.GeneratorType.Element> {
+        var count = 0
+        var generator = self.sequence.generate()
+        return GeneratorOf<S.GeneratorType.Element> {
+            count++
+            if count > self.n {
+                return nil
+            } else {
+                return generator.next()
+            }
+        }
+    }
+}
+
+// a sequence adapter that implements the 'takeWhile' functionality
+struct TakeWhileSequence<S:Sequence>: Sequence {
+    let sequence: S
+    let condition: (S.GeneratorType.Element?) -> Bool
+
+    init(_ sequence:S, _ condition:(S.GeneratorType.Element?) -> Bool) {
+        self.sequence = sequence
+        self.condition = condition
+    }
+
+    func generate() -> GeneratorOf<S.GeneratorType.Element> {
+        var generator = self.sequence.generate()
+        var endConditionMet = false
+        return GeneratorOf<S.GeneratorType.Element> {
+            let next: S.GeneratorType.Element? = generator.next()
+            if !endConditionMet {
+                endConditionMet = !self.condition(next)
+            }
+            if endConditionMet {
+                return nil
+            } else {
+                return next
+            }
+        }
+    }
+}