Upgrade to Elm 0.18 and move repository

A salted-earth approach to package resolution woes.

Package version is reset to v1.0.0 to indulge elm-package.

elm-package.json

@@ -1,5 +1,5 @@
 {
-    "version": "1.0.1",
+    "version": "1.0.0",
     "summary": "A minimal functional core for relational programming",
     "repository": "https://github.com/tapeinosyne/elm-microkanren.git",
     "license": "BSD3",
@@ -11,7 +11,7 @@
         "MicroKanren.Operators"
     ],
     "dependencies": {
-        "elm-lang/core": "4.0.0 <= v < 5.0.0"
+        "elm-lang/core": "5.0.0 <= v < 6.0.0"
     },
-    "elm-version": "0.17.0 <= v < 0.18.0"
-}
+    "elm-version": "0.18.0 <= v < 0.19.0"
+}

src/MicroKanren.elm

@@ -109,23 +109,23 @@ potentially extending it.
 - `LVal` values unify when they are equivalent under Elm's native `(==)`.
   `s` is returned unchanged.
 - Pairs unify when their terms unify pairwise.
-- Finally, an `LVar` variable and an `LVal` value unify under an extended substitution `s'`,
+- Finally, an `LVar` variable and an `LVal` value unify under an extended substitution `s1`,
   where they form a new binding.
 
 If unification fails, `Nothing` is returned.
 -}
 unify : Term a -> Term a -> Substitution a -> Maybe (Substitution a)
 unify u v s =
-  let u' = walk u s
-      v' = walk v s
+  let u1 = walk u s
+      v1 = walk v s
   in
-      case (u', v') of
+      case (u1, v1) of
         (LVar n, LVar m) -> if n == m then Just s else Nothing
         (LVal x, LVal y) -> if x == y then Just s else Nothing
-        (LVar n, _) -> Just (extend n v' s)
-        (_, LVar m) -> Just (extend m u' s)
+        (LVar n, _) -> Just (extend n v1 s)
+        (_, LVar m) -> Just (extend m u1 s)
         (Pair x y, Pair x1 y1) -> case unify x x1 s of
-                                    Just s' -> unify y y1 s'
+                                    Just s1 -> unify y y1 s1
                                     Nothing -> Nothing
         _ -> Nothing
 
@@ -153,7 +153,7 @@ bind s g =
 identical : Term a -> Term a -> Goal a
 identical u v =
   \sc -> case unify u v sc.s of
-           Just s' -> unit { sc | s = s' }
+           Just s1 -> unit { sc | s = s1 }
            Nothing -> mzero
 
 {-| Create a goal which introduces a new logic variable for use by another goal. -}
@@ -167,12 +167,12 @@ callFresh f =
 Effectively a binary disjunction of goals. -}
 disjoin : Goal a -> Goal a -> Goal a
 disjoin g1 g2 =
-  \sc -> g1 sc `mplus` g2 sc
+  \sc -> mplus (g1 sc) (g2 sc)
 
 {-| Create a goal which succeeds if the second goal is achievable within the stream
 generated by the first goal.
 
 Effectively a binary conjunction of goals. -}
 conjoin : Goal a -> Goal a -> Goal a
 conjoin g1 g2 =
-  \sc -> g1 sc `bind` g2
+  \sc -> bind (g1 sc) g2