Massive refactor of hash tables..

- Added new support for new Keyable protocol
- Cosmetic changes..

Author: waynewbishop

Source/Extensions/Double.swift

@@ -0,0 +1,19 @@
+//
+//  Float.swift
+//  SwiftStructures
+//
+//  Created by Wayne Bishop on 10/10/17.
+//  Copyright © 2017 Arbutus Software Inc. All rights reserved.
+//
+
+import Foundation
+
+extension Double: Keyable {
+
+    
+    //hash table requirement
+    var keyitem: String {
+        return String(self)
+    }
+    
+}

Source/Extensions/Int.swift

@@ -9,9 +9,15 @@
 import Foundation
 
 
-extension Int {
+extension Int: Keyable {
 
 
+    //hash table requirement
+    var keyitem: String {
+        return String(self)
+    }
+
+    
     //iterates the closure body a specified number of times
     func times(closure:(Int)-> Void) {
         for i in 0...self {

Source/Extensions/Keyable.swift

@@ -0,0 +1,49 @@
+//
+//  Keyable.swift
+//  SwiftStructures
+//
+//  Created by Wayne Bishop on 10/10/17.
+//  Copyright © 2017 Arbutus Software Inc. All rights reserved.
+//
+
+import Foundation
+
+
+//note: an extension on a protocol
+
+extension Keyable {
+    
+
+    func hashkey<T>(for key: String!, using buckets: Array<T>) -> Int {
+        
+        
+        var remainder: Int = 0
+        var divisor: Int = 0
+
+        
+        //trivial case
+        guard key != nil else {
+            return -1
+        }
+        
+        
+        for item in key.unicodeScalars {
+            divisor += Int(item.value)
+        }
+        
+        
+        /*
+         note: modular math is used to calculate a hash value. The bucket count is used
+         as the dividend to ensure all possible outcomes are between 0 and the collection size.
+         */
+        
+        remainder = divisor % buckets.count
+        
+        return remainder
+    }
+    
+}
+
+
+
+

Source/Extensions/Sortable.swift

@@ -14,7 +14,6 @@ import Foundation
 extension Sortable {
 
 
-
     func isSorted<T: Comparable>(_ sequence: Array<T>) -> Bool {
 
 

Source/Extensions/String.swift

@@ -10,21 +10,22 @@ import Foundation
 
 
 
-extension String {
+extension String: Keyable {
 
+    //hash table requirement
+    var keyitem: String {
+        return self
+    }
+
 
     //compute the length
     var length: Int {
-        //return self.characters.count - Swift 3.0
-        return self.count
+       return self.count
     }
 
-    
-    
     //determine if all characters are unique
     func isStringUnique() -> Bool {
 
-        
         //evaluate trival case
         guard self.characters.count < 128 else {
             return false

Source/Factories/Graph.swift

@@ -158,7 +158,6 @@ public class SwiftGraph {
         while frontier.count != 0 {
 
             //support path changes using the greedy approach
-            bestPath = Path()
             var pathIndex: Int = 0
 
 
@@ -228,7 +227,7 @@ public class SwiftGraph {
 
 
     ///an optimized version of Dijkstra's shortest path algorthim
-    func processDijkstraWithHeap(_ source: Vertex, destination: Vertex) -> Path! {
+    func processDijkstraWithHeap(_ source: Vertex, destination: Vertex) -> Path? {
 
 
         let frontier: PathHeap = PathHeap()
@@ -253,14 +252,12 @@ public class SwiftGraph {
 
 
         //construct the best path
-        var bestPath: Path = Path()
-        
-        
         while frontier.count != 0 {
 
             //use the greedy approach to obtain the best path
-            bestPath = Path()
-            bestPath = frontier.peek()
+            guard let bestPath: Path = frontier.peek() else {
+                break
+            }
 
 
             //enumerate the bestPath edges
@@ -294,7 +291,7 @@ public class SwiftGraph {
 
 
         //obtain the shortest path from the heap
-        var shortestPath: Path! = Path()
+        var shortestPath: Path? = Path()
         shortestPath = finalPaths.peek()