Merge branch 'michaeleisel-combinations'

ExSwift/Array.swift

@@ -749,6 +749,41 @@ internal extension Array {
         return result
     }
 
+    /**
+        Returns all of the combinations in the array of the given length
+		
+		:param: length
+		:returns: Combinations
+    */
+    func combination (length: Int) -> [[Element]] {
+        if length < 0 || length > self.count {
+            return []
+        }
+        var indexes: [Int] = (0..<length).toArray()
+        var combinations: [[Element]] = []
+        var offset = self.count - indexes.count
+        while true {
+            var combination: [Element] = []
+            for index in indexes {
+                combination.append(self[index])
+            }
+            combinations.append(combination)
+            var i = indexes.count - 1
+            while i >= 0 && indexes[i] == i + offset {
+                i--
+            }
+            if i < 0 {
+                break
+            }
+            i++
+            var start = indexes[i-1] + 1
+            for j in (i-1)..<indexes.count {
+                indexes[j] = start + j - i + 1
+            }
+        }
+        return combinations
+    }
+
     /**
         Returns the number of elements which meet the condition
 

ExSwift/Range.swift

@@ -57,6 +57,18 @@ internal extension Range {
 
     }
 
+	/**
+		Returns each element of the range in an array
+	
+		:returns: Each element of the range in an array
+	*/
+    func toArray () -> [T] {
+        var result: [T] = []
+        for i in self {
+            result.append(i)
+        }
+        return result
+    }
 }
 
 /**

ExSwift/Sequence.swift

@@ -173,6 +173,19 @@ internal extension SequenceOf {
     func takeWhile (condition:(T?) -> Bool) -> SequenceOf<T>  {
         return SequenceOf(TakeWhileSequence(self, condition))
     }
+
+	/**
+		Returns each element of the sequence in an array
+	
+		:returns: Each element of the sequence in an array
+	*/
+	func toArray () -> [T] {
+		var result: [T] = []
+		for item in self {
+			result.append(item)
+        }
+		return result
+	}
 }
 
 /**

ExSwiftTests/ExSwiftArrayTests.swift

@@ -426,4 +426,15 @@ class ExtensionsArrayTests: XCTestCase {
         XCTAssertEqual(array.uniqueBy({$0 % 3}), [1, 2, 3])
         XCTAssertEqual(array.uniqueBy({$0 < 3}), [1, 3])
     }
+
+    func testCombinations() {
+        XCTAssertEqual(array.combination(-1), [])
+        XCTAssertEqual(array.combination(0), [[]])
+        XCTAssertEqual(array.combination(1), [[1], [2], [3], [4], [5]])
+        XCTAssertEqual(array.combination(2), [[1, 2], [1, 3], [1, 4], [1, 5], [2, 3], [2, 4], [2, 5], [3, 4], [3, 5], [4, 5]])
+        XCTAssertEqual(array.combination(3), [[1, 2, 3], [1, 2, 4], [1, 2, 5], [1, 3, 4], [1, 3, 5], [1, 4, 5], [2, 3, 4], [2, 3, 5], [2, 4, 5], [3, 4, 5]])
+        XCTAssertEqual(array.combination(4), [[1, 2, 3, 4], [1, 2, 3, 5], [1, 2, 4, 5], [1, 3, 4, 5], [2, 3, 4, 5]])
+        XCTAssertEqual(array.combination(5), [[1, 2, 3, 4, 5]])
+        XCTAssertEqual(array.combination(6), [])
+    }
 }