Test recursion on Himotoki

PerformanceTests.swift

import Foundation
import XCTest
import Himotoki

class PerformanceTests: XCTestCase {
    func testRecursion() {
        let JSON = deepNestedJSON(0)
        
        self.measureBlock {
            var t: Test? = decode(JSON!)
            XCTAssert(t?.depth == Test.depth)
        }
    }
}

// copy from https://github.com/robrix/Prelude/blob/master/Prelude%2FFix.swift
func fix<T, U>(f: (T -> U) -> T -> U) -> T -> U {
    return { f(fix(f))($0) }
}

let deepNestedJSON: Int -> [String: AnyObject]? = fix { recur in
    return { n in
        if n <= Test.depth {
            if let r = recur( n + 1 ) {
                return [
                    "a": r,
                    "depth": NSNumber(integer: n)
                ]
            } else {
                return ["depth": NSNumber(integer: n)]
            }
        } else {
            return nil
        }
    }
}

struct Test: Decodable {
    static let depth = 5000
    let depth: Int
    
    static func decode(e: Extractor) -> Test? {
        let key = reduce(1..<depth, "a", {n,_ in return n + ".a" }) + ".depth"
        let create = { Test(depth: $0) }
        return build(
            e <| key
            ).map(create)
    }
}

UseArraySlice.patch

---
 Himotoki/Extractor.swift | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/Himotoki/Extractor.swift b/Himotoki/Extractor.swift
index c9b2c8b..33856c0 100644
--- a/Himotoki/Extractor.swift
+++ b/Himotoki/Extractor.swift
@@ -15,7 +15,7 @@ public final class Extractor {
 
     private func rawValue(key: String) -> AnyObject? {
         if let dictionary = rawValue as? [String: AnyObject] {
-            return valueFor(key.componentsSeparatedByString("."), dictionary)
+            return valueFor(ArraySlice(split(key) {$0 == "."}), dictionary)
         } else {
             return nil
         }
@@ -52,18 +52,18 @@ public final class Extractor {
 }
 
 // Implement it as a tail recursive function.
-private func valueFor(keyPathComponents: [String], dictionary: [String: AnyObject]) -> AnyObject? {
-    if keyPathComponents.isEmpty {
+private func valueFor(keyPathComponents: ArraySlice<String>, dictionary: [String: AnyObject]) -> AnyObject? {
+    if isEmpty(keyPathComponents) {
         return nil
     }
 
-    if let object: AnyObject = dictionary[keyPathComponents.first!] {
+    if let object: AnyObject = dictionary[first(keyPathComponents)!] {
         switch object {
         case is NSNull:
             return nil
 
-        case let dict as [String: AnyObject] where keyPathComponents.count > 1:
-            let tail = Array(keyPathComponents[1..<keyPathComponents.count])
+        case let dict as [String: AnyObject] where count(keyPathComponents) > 1:
+            let tail = dropFirst(keyPathComponents)
             return valueFor(tail, dict)
             
         default:
-- 
2.3.2 (Apple Git-55)

MacBook Pro (Retina, 13-inch, Late 2013) 2.6 GHz Intel Core i5
before: 0.76 sec
after: 0.11 sec