Add basic hierarchy code.

src/CacheSim/Hierarchy.elm

@@ -0,0 +1,23 @@
+module CacheSim.Hierarchy exposing (..)
+import CacheSim.Cache exposing (..)
+
+type alias CacheModelHierarchy = List CacheModel
+type alias CacheHierarchy = List Cache
+
+accessCacheHierarchy : WordAddr -> CacheHierarchy -> Result String (List (AccessEffect Cache)) 
+accessCacheHierarchy wa ch =
+    case ch of
+        [] -> Ok []
+        c::cs ->
+            case accessCache wa c of
+                Ok { result, output } ->
+                    case result of
+                        Hit ->
+                            Ok [ { result = Hit, output = output } ]
+                        Miss ->
+                            Result.map ((::) { result = Miss, output = output }) 
+                                <| accessCacheHierarchy wa cs
+                Err e -> Err e
+
+freshCacheHierarchy : CacheModelHierarchy -> CacheHierarchy
+freshCacheHierarchy cmh = List.map freshCache cmh