Merge pull request #68 from michaeleisel/round_to_nearest

Round to nearest

ExSwift/Double.swift

@@ -78,5 +78,16 @@ public extension Double {
         let rand = Double(arc4random() % (UInt32(RAND_MAX) + 1))
         return ((rand / Double(RAND_MAX)) * diff) + min;
     }
+
+    /**
+        Just like round(), except it supports rounding to an arbitrary number, not just 1
+        Be careful about rounding errors
 
+        :params: increment the increment to round to
+    */
+    func roundToNearest(increment: Double) -> Double {
+        let remainder = self % increment
+        return remainder < increment / 2 ? self - remainder : self - remainder + increment
+    }
+
 }

ExSwiftTests/ExSwiftDoubleTests.swift

@@ -39,5 +39,12 @@ class ExSwiftDoubleTests: XCTestCase {
 
     func testRandom() {
     }
-
+
+    func testRoundToNearest () {
+        XCTAssertEqualWithAccuracy(2.5.roundToNearest(0.3), 2.4, 0.01)
+        XCTAssertEqualWithAccuracy(0.roundToNearest(0.3), 0.0, 0.01)
+        XCTAssertEqualWithAccuracy(4.0.roundToNearest(2), 4.0, 0.01)
+        XCTAssertEqualWithAccuracy(10.0.roundToNearest(3), 9.0, 0.01)
+        XCTAssertEqualWithAccuracy(-2.0.roundToNearest(3), -3.0, 0.01)
+    }
 }