Optimizations for the pure-Lux JVM compiler. [Part 5]

21 files changed, 1272 insertions, 893 deletions

diff --git a/documentation/bookmark/back_end/c++.md b/documentation/bookmark/back_end/c++.md
index b7eb8b3f3..bf1d04548 100644
--- a/documentation/bookmark/back_end/c++.md
+++ b/documentation/bookmark/back_end/c++.md
@@ -16,3 +16,7 @@
 
 0. [vcpkg](https://vcpkg.io/en/index.html)
 
+# constexpr
+
+0. [Your New Mental Model of constexpr - Jason Turner - CppCon 2021](https://www.youtube.com/watch?v=MdrfPSUtMVM)
+
diff --git a/stdlib/source/library/lux.lux b/stdlib/source/library/lux.lux
index e46090db0..657bc4faa 100644
--- a/stdlib/source/library/lux.lux
+++ b/stdlib/source/library/lux.lux
@@ -3363,17 +3363,6 @@
     {#None}
     (failure "Wrong syntax for type:")))
 
-(template [<name> <to>]
-  [(def: .public (<name> value)
-     (-> (I64 Any) <to>)
-     (:as <to> value))]
-
-  [i64 I64]
-  [nat Nat]
-  [int Int]
-  [rev Rev]
-  )
-
 (type: Referrals
   (Variant
    {#All}
@@ -4819,6 +4808,16 @@
     {#None}
     (failure (..wrong_syntax_error (symbol ..template:)))))
 
+(template [<name> <to>]
+  [(template: .public (<name> it)
+     [(..|> it (..: (..I64 ..Any)) (..:as <to>))])]
+
+  [i64 ..I64]
+  [nat ..Nat]
+  [int ..Int]
+  [rev ..Rev]
+  )
+
 (macro: .public (as_is tokens compiler)
   {#Right [compiler tokens]})
 
diff --git a/stdlib/source/library/lux/control/maybe.lux b/stdlib/source/library/lux/control/maybe.lux
index 597953a64..af48067c5 100644
--- a/stdlib/source/library/lux/control/maybe.lux
+++ b/stdlib/source/library/lux/control/maybe.lux
@@ -129,7 +129,7 @@
   (case tokens
     (^ (.list else maybe))
     (let [g!temp (: Code [location.dummy {.#Symbol ["" ""]}])]
-      {.#Right [state (.list (` (case (~ maybe)
+      {.#Right [state (.list (` (.case (~ maybe)
                                   {.#Some (~ g!temp)}
                                   (~ g!temp)
 
diff --git a/stdlib/source/library/lux/control/parser/binary.lux b/stdlib/source/library/lux/control/parser/binary.lux
index a8e41dcc9..f2b2e7f5d 100644
--- a/stdlib/source/library/lux/control/parser/binary.lux
+++ b/stdlib/source/library/lux/control/parser/binary.lux
@@ -163,7 +163,7 @@
   [(`` (def: .public <name>
          (Parser Binary)
          (do //.monad
-           [size (//#each .nat <bits>)]
+           [size (//#each (|>> .nat) <bits>)]
            (..segment size))))]
 
   [08 binary/8  ..bits/8]
diff --git a/stdlib/source/library/lux/data/binary.lux b/stdlib/source/library/lux/data/binary.lux
index 8df174ce5..be2a236ea 100644
--- a/stdlib/source/library/lux/data/binary.lux
+++ b/stdlib/source/library/lux/data/binary.lux
@@ -1,7 +1,6 @@
 (.using
  [library
   [lux "*"
-   ["@" target]
    ["[0]" ffi]
    [abstract
     [equivalence {"+" Equivalence}]
@@ -13,7 +12,8 @@
     [text
      ["%" format]]
     [collection
-     ["[0]" array]]]
+     ["[0]" array
+      [\\unsafe {"+"}]]]]
    [math
     [number
      ["n" nat]]]]]
diff --git a/stdlib/source/library/lux/data/collection/array.lux b/stdlib/source/library/lux/data/collection/array.lux
index 437c80bfa..cef8b64c0 100644
--- a/stdlib/source/library/lux/data/collection/array.lux
+++ b/stdlib/source/library/lux/data/collection/array.lux
@@ -1,424 +1,149 @@
 (.using
  [library
   [lux {"-" list}
-   ["@" target]
    [abstract
     [monoid {"+" Monoid}]
     [functor {"+" Functor}]
     [equivalence {"+" Equivalence}]
     [mix {"+" Mix}]
     [predicate {"+" Predicate}]]
-   [control
-    ["[0]" maybe]]
    [data
-    ["[0]" product]
     [collection
-     ["[0]" list ("[1]#[0]" mix)]]]
-   [math
-    [number
-     ["n" nat]]]]])
+     ["[0]" list]]]]]
+ ["!" \\unsafe])
 
 (def: .public type_name
-  "#Array")
+  !.type)
 
-(type: .public (Array a)
-  {.#Primitive ..type_name {.#Item a {.#End}}})
+(type: .public Array
+  !.Array)
 
-(with_expansions [<index_type> (Primitive "java.lang.Long")
-                  <elem_type> (Primitive "java.lang.Object")
-                  <array_type> (type (Array <elem_type>))]
-  (for [@.jvm
-        (template: (!int value)
-          [(|> value
-               (:as <index_type>)
-               "jvm object cast"
-               "jvm conversion long-to-int")])]
-       (as_is))
-  
-  (def: .public (empty size)
-    (All (_ a) (-> Nat (Array a)))
-    (for [@.old
-          (:expected ("jvm anewarray" "(java.lang.Object )" size))
-
-          @.jvm
-          (|> size
-              !int
-              "jvm array new object"
-              (: <array_type>)
-              :expected)
-
-          @.js ("js array new" size)
-          @.python ("python array new" size)
-          @.lua ("lua array new" size)
-          @.ruby ("ruby array new" size)
-          @.php ("php array new" size)
-          @.scheme ("scheme array new" size)]))
-
-  (def: .public (size array)
-    (All (_ a) (-> (Array a) Nat))
-    (for [@.old
-          ("jvm arraylength" array)
-
-          @.jvm
-          (|> array
-              (:as <array_type>)
-              "jvm array length object"
-              "jvm conversion int-to-long"
-              "jvm object cast"
-              (: <index_type>)
-              (:as Nat))
-
-          @.js ("js array length" array)
-          @.python ("python array length" array)
-          @.lua ("lua array length" array)
-          @.ruby ("ruby array length" array)
-          @.php ("php array length" array)
-          @.scheme ("scheme array length" array)]))
-
-  (template: (!read! <read!> <null?>)
-    [(let [output (<read!> index array)]
-       (if (<null?> output)
-         {.#None}
-         {.#Some output}))])
-
-  (def: .public (read! index array)
-    (All (_ a)
-      (-> Nat (Array a) (Maybe a)))
-    (if (n.< (size array) index)
-      (for [@.old
-            (let [value ("jvm aaload" array index)]
-              (if ("jvm object null?" value)
-                {.#None}
-                {.#Some value}))
-
-            @.jvm
-            (let [value (|> array
-                            (:as <array_type>)
-                            ("jvm array read object" (!int index)))]
-              (if ("jvm object null?" value)
-                {.#None}
-                {.#Some (:expected value)}))
-
-            @.js (!read! "js array read" "js object undefined?")
-            @.python (!read! "python array read" "python object none?")
-            @.lua (!read! "lua array read" "lua object nil?")
-            @.ruby (!read! "ruby array read" "ruby object nil?")
-            @.php (!read! "php array read" "php object null?")
-            @.scheme (!read! "scheme array read" "scheme object nil?")])
-      {.#None}))
-
-  (def: .public (write! index value array)
-    (All (_ a)
-      (-> Nat a (Array a) (Array a)))
-    (for [@.old
-          ("jvm aastore" array index value)
+(def: .public empty
+  (All (_ a) (-> Nat (Array a)))
+  (|>> !.empty))
 
-          @.jvm
-          (|> array
-              (:as <array_type>)
-              ("jvm array write object" (!int index) (:as <elem_type> value))
-              :expected)
+(def: .public size
+  (All (_ a) (-> (Array a) Nat))
+  (|>> !.size))
 
-          @.js ("js array write" index value array)
-          @.python ("python array write" index value array)
-          @.lua ("lua array write" index value array)
-          @.ruby ("ruby array write" index value array)
-          @.php ("php array write" index value array)
-          @.scheme ("scheme array write" index value array)]))
+(def: .public (read! index array)
+  (All (_ a)
+    (-> Nat (Array a) (Maybe a)))
+  (if (!.lacks? index array)
+    {.#None}
+    {.#Some (!.item index array)}))
 
-  (def: .public (delete! index array)
-    (All (_ a)
-      (-> Nat (Array a) (Array a)))
-    (if (n.< (size array) index)
-      (for [@.old
-            (write! index (:expected ("jvm object null")) array)
+(def: .public (write! index value array)
+  (All (_ a)
+    (-> Nat a (Array a) (Array a)))
+  (!.has! index value array))
 
-            @.jvm
-            (write! index (:expected (: <elem_type> ("jvm object null"))) array)
+(def: .public (delete! index array)
+  (All (_ a)
+    (-> Nat (Array a) (Array a)))
+  (!.lacks! index array))
 
-            @.js ("js array delete" index array)
-            @.python ("python array delete" index array)
-            @.lua ("lua array delete" index array)
-            @.ruby ("ruby array delete" index array)
-            @.php ("php array delete" index array)
-            @.scheme ("scheme array delete" index array)])
-      array))
-  )
+(def: .public (lacks? index array)
+  (All (_ a)
+    (-> Nat (Array a) Bit))
+  (!.lacks? index array))
 
 (def: .public (contains? index array)
   (All (_ a)
     (-> Nat (Array a) Bit))
-  (case (..read! index array)
-    {.#Some _}
-    true
-
-    _
-    false))
+  (not (!.lacks? index array)))
 
-(def: .public (update! index transform array)
+(def: .public (update! index $ array)
   (All (_ a)
     (-> Nat (-> a a) (Array a) (Array a)))
-  (case (read! index array)
-    {.#None}
-    array
-
-    {.#Some value}
-    (write! index (transform value) array)))
+  (!.revised! index $ array))
 
 (def: .public (upsert! index default transform array)
   (All (_ a)
     (-> Nat a (-> a a) (Array a) (Array a)))
-  (write! index
-          (|> array (read! index) (maybe.else default) transform)
-          array))
+  (!.upsert! index default transform array))
 
 (def: .public (copy! length src_start src_array dest_start dest_array)
   (All (_ a)
     (-> Nat Nat (Array a) Nat (Array a)
         (Array a)))
-  (if (n.= 0 length)
-    dest_array
-    (list#mix (function (_ offset target)
-                (case (read! (n.+ offset src_start) src_array)
-                  {.#None}
-                  target
-                  
-                  {.#Some value}
-                  (write! (n.+ offset dest_start) value target)))
-              dest_array
-              (list.indices length))))
+  (!.copy! length src_start src_array dest_start dest_array))
 
-(def: .public (occupancy array)
+(def: .public occupancy
   (All (_ a) (-> (Array a) Nat))
-  (list#mix (function (_ idx count)
-              (case (read! idx array)
-                {.#None}
-                count
-                
-                {.#Some _}
-                (++ count)))
-            0
-            (list.indices (size array))))
+  (|>> !.occupancy))
 
-(def: .public (vacancy array)
+(def: .public vacancy
   (All (_ a) (-> (Array a) Nat))
-  (n.- (..occupancy array) (..size array)))
+  (|>> !.vacancy))
 
-(def: .public (filter! p xs)
+(def: .public (filter! ? it)
   (All (_ a)
     (-> (Predicate a) (Array a) (Array a)))
-  (list#mix (function (_ idx xs')
-              (case (read! idx xs)
-                {.#None}
-                xs'
-
-                {.#Some x}
-                (if (p x)
-                  xs'
-                  (delete! idx xs'))))
-            xs
-            (list.indices (size xs))))
+  (!.only! ? it))
 
-(def: .public (example p xs)
+(def: .public (example ? it)
   (All (_ a)
     (-> (Predicate a) (Array a) (Maybe a)))
-  (let [arr_size (size xs)]
-    (loop [idx 0]
-      (if (n.< arr_size idx)
-        (case (read! idx xs)
-          {.#None}
-          (again (++ idx))
-          
-          {.#Some x}
-          (if (p x)
-            {.#Some x}
-            (again (++ idx))))
-        {.#None}))))
+  (!.example ? it))
 
-(def: .public (example+ p xs)
+(def: .public (example+ ? it)
   (All (_ a)
     (-> (-> Nat a Bit) (Array a) (Maybe [Nat a])))
-  (let [arr_size (size xs)]
-    (loop [idx 0]
-      (if (n.< arr_size idx)
-        (case (read! idx xs)
-          {.#None}
-          (again (++ idx))
-          
-          {.#Some x}
-          (if (p idx x)
-            {.#Some [idx x]}
-            (again (++ idx))))
-        {.#None}))))
+  (!.example' ? it))
 
-(def: .public (clone xs)
+(def: .public clone
   (All (_ a) (-> (Array a) (Array a)))
-  (let [arr_size (size xs)]
-    (list#mix (function (_ idx ys)
-                (case (read! idx xs)
-                  {.#None}
-                  ys
+  (|>> !.clone))
 
-                  {.#Some x}
-                  (write! idx x ys)))
-              (empty arr_size)
-              (list.indices arr_size))))
-
-(def: .public (of_list xs)
+(def: .public of_list
   (All (_ a) (-> (List a) (Array a)))
-  (product.right (list#mix (function (_ x [idx arr])
-                             [(++ idx) (write! idx x arr)])
-                           [0 (empty (list.size xs))]
-                           xs)))
-
-(def: underflow
-  Nat
-  (-- 0))
-
-(def: (list|-default array empty)
-  (All (_ a) (-> (Array a) (List a) (List a)))
-  (loop [idx (-- (size array))
-         output empty]
-    (case idx
-      (^ (static ..underflow))
-      output
-
-      _
-      (again (-- idx)
-             (case (read! idx array)
-               {.#Some head}
-               {.#Item head output}
-
-               {.#None}
-               output)))))
-
-(def: (list|+default default array)
-  (All (_ a) (-> a (Array a) (List a)))
-  (loop [idx (-- (size array))
-         output (`` (: (List (~~ (:of default)))
-                       {.#End}))]
-    (case idx
-      (^ (static ..underflow))
-      output
-
-      _
-      (again (-- idx)
-             {.#Item (maybe.else default (read! idx array))
-                     output}))))
+  (|>> !.of_list))
 
 (def: .public (list default array)
   (All (_ a) (-> (Maybe a) (Array a) (List a)))
-  (case default
-    {.#Some default}
-    (list|+default default array)
-    
-    {.#None}
-    (list|-default array {.#End})))
+  (!.list default array))
 
-(implementation: .public (equivalence (^open ",#[0]"))
+(implementation: .public (equivalence //)
   (All (_ a) (-> (Equivalence a) (Equivalence (Array a))))
   
-  (def: (= xs ys)
-    (let [sxs (size xs)
-          sxy (size ys)]
-      (and (n.= sxy sxs)
-           (list#mix (function (_ idx prev)
-                       (and prev
-                            (case [(read! idx xs) (read! idx ys)]
-                              [{.#None} {.#None}]
-                              true
-
-                              [{.#Some x} {.#Some y}]
-                              (,#= x y)
-
-                              _
-                              false)))
-                     true
-                     (list.indices sxs))))))
+  (def: (= left/* right/*)
+    (!.= // left/* right/*)))
 
 (implementation: .public monoid
   (All (_ a) (Monoid (Array a)))
   
-  (def: identity (empty 0))
+  (def: identity (!.empty 0))
 
-  (def: (composite xs ys)
-    (let [sxs (size xs)
-          sxy (size ys)]
-      (|> (empty (n.+ sxy sxs))
-          (copy! sxs 0 xs 0)
-          (copy! sxy 0 ys sxs)))))
-
-(implementation: .public functor
-  (Functor Array)
-  
-  (def: (each f ma)
-    (let [arr_size (size ma)]
-      (if (n.= 0 arr_size)
-        (empty arr_size)
-        (list#mix (function (_ idx mb)
-                    (case (read! idx ma)
-                      {.#None}
-                      mb
-
-                      {.#Some x}
-                      (write! idx (f x) mb)))
-                  (empty arr_size)
-                  (list.indices arr_size))
-        ))))
+  (def: (composite left/* right/*)
+    (!.composite left/* right/*)))
 
 (implementation: .public mix
   (Mix Array)
   
-  (def: (mix f init xs)
-    (let [arr_size (size xs)]
-      (loop [so_far init
-             idx 0]
-        (if (n.< arr_size idx)
-          (case (read! idx xs)
-            {.#None}
-            (again so_far (++ idx))
+  (def: (mix $ init it)
+    (!.mix (function (_ index partial total)
+             ($ partial total))
+           init
+           it)))
 
-            {.#Some value}
-            (again (f value so_far) (++ idx)))
-          so_far)))))
+(implementation: .public functor
+  (Functor Array)
+  
+  (def: (each $ input)
+    (!.each $ input)))
 
-(template [<name> <init> <op>]
-  [(def: .public (<name> predicate)
-     (All (_ a)
-       (-> (Predicate a) (Predicate (Array a))))
-     (function (_ array)
-       (let [size (..size array)]
-         (loop [idx 0]
-           (if (n.< size idx)
-             (case (..read! idx array)
-               {.#Some value}
-               (<op> (predicate value)
-                     (again (++ idx)))
-               
-               {.#None}
-               (again (++ idx)))
-             <init>)))))]
+(def: .public (every? ? it)
+  (All (_ a)
+    (-> (Predicate a) (Predicate (Array a))))
+  (!.every? ? it))
 
-  [every? true  and]
-  [any?   false or]
-  )
+(def: .public (any? ? it)
+  (All (_ a)
+    (-> (Predicate a) (Predicate (Array a))))
+  (!.any? ? it))
 
-(def: .public (one check items)
+(def: .public (one ? it)
   (All (_ a b)
     (-> (-> a (Maybe b)) (Array a) (Maybe b)))
-  (let [size (..size items)]
-    (loop [idx 0]
-      (if (n.< size idx)
-        (with_expansions [<again> (again (++ idx))]
-          (case (..read! idx items)
-            {.#Some input}
-            (case (check input)
-              {.#None}
-              <again>
-
-              output
-              output)
-            
-            {.#None}
-            <again>))
-        {.#None}))))
+  (!.one ? it))
diff --git a/stdlib/source/library/lux/data/collection/dictionary.lux b/stdlib/source/library/lux/data/collection/dictionary.lux
index ee7b7cb7d..e61a79230 100644
--- a/stdlib/source/library/lux/data/collection/dictionary.lux
+++ b/stdlib/source/library/lux/data/collection/dictionary.lux
@@ -1,23 +1,24 @@
 (.using
-  [library
-   [lux "*"
-    [abstract
-     [hash {"+" Hash}]
-     [equivalence {"+" Equivalence}]
-     [functor {"+" Functor}]]
-    [control
-     ["[0]" maybe]
-     ["[0]" try {"+" Try}]
-     ["[0]" exception {"+" exception:}]]
-    [data
-     ["[0]" product]
-     [collection
-      ["[0]" list ("[1]#[0]" mix functor monoid)]
-      ["[0]" array {"+" Array} ("[1]#[0]" functor mix)]]]
-    [math
-     ["[0]" number
-      ["n" nat]
-      ["[0]" i64]]]]])
+ [library
+  [lux "*"
+   [abstract
+    [hash {"+" Hash}]
+    [equivalence {"+" Equivalence}]
+    [functor {"+" Functor}]]
+   [control
+    ["[0]" maybe]
+    ["[0]" try {"+" Try}]
+    ["[0]" exception {"+" exception:}]]
+   [data
+    ["[0]" product]
+    [collection
+     ["[0]" list ("[1]#[0]" mix functor monoid)]
+     ["[0]" array "_"
+      ["[1]" \\unsafe {"+" Array}]]]]
+   [math
+    ["[0]" number
+     ["n" nat]
+     ["[0]" i64]]]]])
 
 ... This implementation of Hash Array Mapped Trie (HAMT) is based on
 ... Clojure's PersistentHashMap implementation.
@@ -136,20 +137,20 @@
   (let [old_size (array.size old_array)]
     (|> (array.empty (++ old_size))
         (array.copy! idx 0 old_array 0)
-        (array.write! idx value)
+        (array.has! idx value)
         (array.copy! (n.- idx old_size) idx old_array (++ idx)))))
 
 ... Creates a copy of an array with an index set to a particular value.
 (def: (array#revised idx value array)
   (All (_ a) (-> Index a (Array a) (Array a)))
-  (|> array array.clone (array.write! idx value)))
+  (|> array array.clone (array.has! idx value)))
 
 ... Creates a clone of the array, with an empty position at index.
 (def: (array#clear idx array)
   (All (_ a) (-> Index (Array a) (Array a)))
   (|> array
       array.clone
-      (array.delete! idx)))
+      (array.lacks! idx)))
 
 ... Shrinks a copy of the array by removing the space at index.
 (def: (array#lacks idx array)
@@ -229,7 +230,7 @@
 (def: (collision_index key_hash key colls)
   (All (_ k v) (-> (Hash k) k (Collisions k v) (Maybe Index)))
   (# maybe.monad each product.left
-     (array.example+ (function (_ idx [key' val'])
+     (array.example' (function (_ idx [key' val'])
                        (# key_hash = key key'))
                      colls)))
 
@@ -239,14 +240,13 @@
   (All (_ k v) (-> Index (Hierarchy k v) [Bit_Map (Base k v)]))
   (product.right (list#mix (function (_ idx [insertion_idx node])
                              (let [[bitmap base] node]
-                               (case (array.read! idx h_array)
-                                 {.#None}          [insertion_idx node]
-                                 {.#Some sub_node} (if (n.= except_idx idx)
-                                                     [insertion_idx node]
-                                                     [(++ insertion_idx)
-                                                      [(with_bit_position (to_bit_position idx) bitmap)
-                                                       (array.write! insertion_idx {.#Left sub_node} base)]])
-                                 )))
+                               (if (array.lacks? idx h_array)
+                                 [insertion_idx node]
+                                 (if (n.= except_idx idx)
+                                   [insertion_idx node]
+                                   [(++ insertion_idx)
+                                    [(with_bit_position (to_bit_position idx) bitmap)
+                                     (array.has! insertion_idx {.#Left (array.item idx h_array)} base)]]))))
                            [0 [clean_bitmap
                                (array.empty (-- h_size))]]
                            (list.indices (array.size h_array)))))
@@ -267,17 +267,14 @@
                              (if (with_bit_position? (to_bit_position hierarchy_idx)
                                    bitmap)
                                [(++ base_idx)
-                                (case (array.read! base_idx base)
-                                  {.#Some {.#Left sub_node}}
-                                  (array.write! hierarchy_idx sub_node h_array)
-
-                                  {.#Some {.#Right [key' val']}}
-                                  (array.write! hierarchy_idx
-                                                (node#has (level_up level) (# key_hash hash key') key' val' key_hash empty_node)
-                                                h_array)
-
-                                  {.#None}
-                                  (undefined))]
+                                (case (array.item base_idx base)
+                                  {.#Left sub_node}
+                                  (array.has! hierarchy_idx sub_node h_array)
+
+                                  {.#Right [key' val']}
+                                  (array.has! hierarchy_idx
+                                              (node#has (level_up level) (# key_hash hash key') key' val' key_hash ..empty_node)
+                                              h_array))]
                                default))
                            [0
                             (array.empty hierarchy_nodes_size)]
@@ -302,12 +299,9 @@
     ... a sub-node. If impossible, introduce a new singleton sub-node.
     {#Hierarchy _size hierarchy}
     (let [idx (level_index level hash)
-          [_size' sub_node] (case (array.read! idx hierarchy)
-                              {.#Some sub_node}
-                              [_size sub_node]
-
-                              _
-                              [(++ _size) empty_node])]
+          [_size' sub_node] (if (not (array.lacks? idx hierarchy))
+                              [_size (array.item idx hierarchy)]
+                              [(++ _size) ..empty_node])]
       {#Hierarchy _size'
                   (array#revised idx (node#has (level_up level) hash key val key_hash sub_node)
                                  hierarchy)})
@@ -319,19 +313,19 @@
       (if (with_bit_position? bit bitmap)
         ... If so...
         (let [idx (base_index bit bitmap)]
-          (case (array.read! idx base)
-            ... If it's being used by a node, add the KV to it.
-            {.#Some {.#Left sub_node}}
-            (let [sub_node' (node#has (level_up level) hash key val key_hash sub_node)]
-              {#Base bitmap (array#revised idx {.#Left sub_node'} base)})
-
-            ... Otherwise, if it's being used by a KV, compare the keys.
-            {.#Some {.#Right key' val'}}
-            (if (# key_hash = key key')
-              ... If the same key is found, replace the value.
-              {#Base bitmap (array#revised idx {.#Right key val} base)}
-              ... Otherwise, compare the hashes of the keys.
-              {#Base bitmap (array#revised idx
+          {#Base bitmap (case (array.item idx base)
+                          ... If it's being used by a node, add the KV to it.
+                          {.#Left sub_node}
+                          (let [sub_node' (node#has (level_up level) hash key val key_hash sub_node)]
+                            (array#revised idx {.#Left sub_node'} base))
+
+                          ... Otherwise, if it's being used by a KV, compare the keys.
+                          {.#Right key' val'}
+                          (array#revised idx
+                                         (if (# key_hash = key key')
+                                           ... If the same key is found, replace the value.
+                                           {.#Right key val}
+                                           ... Otherwise, compare the hashes of the keys.
                                            {.#Left (let [hash' (# key_hash hash key')]
                                                      (if (n.= hash hash')
                                                        ... If the hashes are
@@ -339,21 +333,18 @@
                                                        ... #Collisions node
                                                        ... is added.
                                                        {#Collisions hash (|> (array.empty 2)
-                                                                             (array.write! 0 [key' val'])
-                                                                             (array.write! 1 [key val]))}
+                                                                             (array.has! 0 [key' val'])
+                                                                             (array.has! 1 [key val]))}
                                                        ... Otherwise, one can
                                                        ... just keep using
                                                        ... #Base nodes, so
                                                        ... add both KV-pairs
                                                        ... to the empty one.
                                                        (let [next_level (level_up level)]
-                                                         (|> empty_node
+                                                         (|> ..empty_node
                                                              (node#has next_level hash' key' val' key_hash)
-                                                             (node#has next_level hash  key  val key_hash)))))}
-                                           base)})
-
-            {.#None}
-            (undefined)))
+                                                             (node#has next_level hash  key  val key_hash)))))})
+                                         base))})
         ... However, if the Bit_Position has not been used yet, check
         ... whether this #Base node is ready for a promotion.
         (let [base_count (bitmap_size bitmap)]
@@ -365,10 +356,11 @@
             ... Otherwise, promote it to a #Hierarchy node, and add the new
             ... KV-pair as a singleton node to it.
             {#Hierarchy (++ base_count)
-                        (|> base
-                            (promotion node#has key_hash level bitmap)
-                            (array.write! (level_index level hash)
-                                          (node#has (level_up level) hash key val key_hash empty_node)))}))))
+                        (let [... TODO: These bindings were established to get around a compilation error. Fix and inline!
+                              index (level_index level hash)
+                              item (node#has (level_up level) hash key val key_hash ..empty_node)
+                              array (promotion node#has key_hash level bitmap base)]
+                          (array.has! index item array))}))))
     
     ... For #Collisions nodes, compare the hashes.
     {#Collisions _hash _colls}
@@ -388,7 +380,7 @@
       ... contains the old #Collisions node, plus the new KV-pair.
       (|> {#Base (level_bit_position level _hash)
                  (|> (array.empty 1)
-                     (array.write! 0 {.#Left node}))}
+                     (array.has! 0 {.#Left node}))}
           (node#has level hash key val key_hash)))
     ))
 
@@ -399,14 +391,12 @@
     ... the Hash-Code.
     {#Hierarchy h_size h_array}
     (let [idx (level_index level hash)]
-      (case (array.read! idx h_array)
+      (if (array.lacks? idx h_array)
         ... If not, there's nothing to remove.
-        {.#None}
         node
-
         ... But if there is, try to remove the key from the sub-node.
-        {.#Some sub_node}
-        (let [sub_node' (node#lacks (level_up level) hash key key_hash sub_node)]
+        (let [sub_node (array.item idx h_array)
+              sub_node' (node#lacks (level_up level) hash key key_hash sub_node)]
           ... Then check if a removal was actually done.
           (if (same? sub_node sub_node')
             ... If not, then there's nothing to change here either.
@@ -428,10 +418,10 @@
     (let [bit (level_bit_position level hash)]
       (if (with_bit_position? bit bitmap)
         (let [idx (base_index bit bitmap)]
-          (case (array.read! idx base)
+          (case (array.item idx base)
             ... If set, check if it's a sub_node, and remove the KV
             ... from it.
-            {.#Some {.#Left sub_node}}
+            {.#Left sub_node}
             (let [sub_node' (node#lacks (level_up level) hash key key_hash sub_node)]
               ... Verify that it was removed.
               (if (same? sub_node sub_node')
@@ -442,7 +432,7 @@
                   ...# ... figure out whether that's the only position left.
                   (if (only_bit_position? bit bitmap)
                     ... If so, removing it leaves this node empty too.
-                    empty_node
+                    ..empty_node
                     ... But if not, then just unset the position and
                     ... remove the node.
                     {#Base (without_bit_position bit bitmap)
@@ -453,17 +443,14 @@
                          (array#revised idx {.#Left sub_node'} base)})))
 
             ... If, however, there was a KV-pair instead of a sub-node.
-            {.#Some {.#Right [key' val']}}
+            {.#Right [key' val']}
             ... Check if the keys match.
             (if (# key_hash = key key')
               ... If so, remove the KV-pair and unset the Bit_Position.
               {#Base (without_bit_position bit bitmap)
                      (array#lacks idx base)}
               ... Otherwise, there's nothing to remove.
-              node)
-
-            {.#None}
-            (undefined)))
+              node)))
         ... If the Bit_Position is not set, there's nothing to remove.
         node))
 
@@ -479,7 +466,7 @@
       (if (n.= 1 (array.size _colls))
         ... If there's only one left, then removing it leaves us with
         ... an empty node.
-        empty_node
+        ..empty_node
         ... Otherwise, just shrink the array by removing the KV-pair.
         {#Collisions _hash (array#lacks idx _colls)}))
     ))
@@ -489,25 +476,23 @@
   (case node
     ... For #Hierarchy nodes, just look-up the key on its children.
     {#Hierarchy _size hierarchy}
-    (case (array.read! (level_index level hash) hierarchy)
-      {.#None}          {.#None}
-      {.#Some sub_node} (node#value (level_up level) hash key key_hash sub_node))
+    (let [index (level_index level hash)]
+      (if (array.lacks? index hierarchy)
+        {.#None}
+        (node#value (level_up level) hash key key_hash (array.item index hierarchy))))
 
     ... For #Base nodes, check the leaves, and recursively check the branches.
     {#Base bitmap base}
     (let [bit (level_bit_position level hash)]
       (if (with_bit_position? bit bitmap)
-        (case (array.read! (base_index bit bitmap) base)
-          {.#Some {.#Left sub_node}}
+        (case (array.item (base_index bit bitmap) base)
+          {.#Left sub_node}
           (node#value (level_up level) hash key key_hash sub_node)
 
-          {.#Some {.#Right [key' val']}}
+          {.#Right [key' val']}
           (if (# key_hash = key key')
             {.#Some val'}
-            {.#None})
-
-          {.#None}
-          (undefined))
+            {.#None}))
         {.#None}))
 
     ... For #Collisions nodes, do a linear scan of all the known KV-pairs.
@@ -521,14 +506,20 @@
   (All (_ k v) (-> (Node k v) Nat))
   (case node
     {#Hierarchy _size hierarchy}
-    (array#mix n.+ 0 (array#each node#size hierarchy))
+    (array.mix (function (_ _ item total)
+                 (n.+ item total))
+               0
+               (array.each node#size hierarchy))
     
     {#Base _ base}
-    (array#mix n.+ 0 (array#each (function (_ sub_node')
-                                   (case sub_node'
-                                     {.#Left sub_node} (node#size sub_node)
-                                     {.#Right _}       1))
-                                 base))
+    (array.mix (function (_ _ item total)
+                 (n.+ item total))
+               0
+               (array.each (function (_ sub_node')
+                             (case sub_node'
+                               {.#Left sub_node} (node#size sub_node)
+                               {.#Right _}       1))
+                           base))
 
     {#Collisions hash colls}
     (array.size colls)
@@ -538,13 +529,13 @@
   (All (_ k v a) (-> (-> [k v] a a) a (Node k v) a))
   (case node
     {#Hierarchy _size hierarchy}
-    (array#mix (function (_ sub_node current)
+    (array.mix (function (_ _ sub_node current)
                  (node#mix f current sub_node))
                init
                hierarchy)
 
     {#Base bitmap base}
-    (array#mix (function (_ branch current)
+    (array.mix (function (_ _ branch current)
                  (case branch
                    {.#Left sub_node}
                    (node#mix f current sub_node)
@@ -555,7 +546,10 @@
                base)
     
     {#Collisions hash colls}
-    (array#mix f init colls)))
+    (array.mix (function (_ _ item total)
+                 (f item total))
+               init
+               colls)))
 
 (def: node#entries
   (All (_ k v) (-> (Node k v) (List [k v])))
@@ -575,7 +569,7 @@
 (def: .public (empty key_hash)
   (All (_ k v) (-> (Hash k) (Dictionary k v)))
   [#hash key_hash
-   #root empty_node])
+   #root ..empty_node])
 
 (def: .public (has key val dict)
   (All (_ k v) (-> k v (Dictionary k v) (Dictionary k v)))
@@ -714,10 +708,10 @@
   (def: (each f fa)
     (case fa
       {#Hierarchy size hierarchy}
-      {#Hierarchy size (array#each (each f) hierarchy)}
+      {#Hierarchy size (array.each (each f) hierarchy)}
       
       {#Base bitmap base}
-      {#Base bitmap (array#each (function (_ either)
+      {#Base bitmap (array.each (function (_ either)
                                   (case either
                                     {.#Left fa'}
                                     {.#Left (each f fa')}
@@ -727,7 +721,7 @@
                                 base)}
       
       {#Collisions hash collisions}
-      {#Collisions hash (array#each (function (_ [k v])
+      {#Collisions hash (array.each (function (_ [k v])
                                       [k (f v)])
                                     collisions)})))
 
diff --git a/stdlib/source/library/lux/data/collection/sequence.lux b/stdlib/source/library/lux/data/collection/sequence.lux
index 746654c57..01a33b7c7 100644
--- a/stdlib/source/library/lux/data/collection/sequence.lux
+++ b/stdlib/source/library/lux/data/collection/sequence.lux
@@ -14,7 +14,7 @@
     [mix {"+" Mix}]
     [predicate {"+" Predicate}]]
    [control
-    ["[0]" maybe]
+    ["[0]" maybe ("[1]#[0]" functor)]
     ["[0]" try {"+" Try}]
     ["[0]" exception {"+" exception:}]
     ["<>" parser
@@ -23,7 +23,8 @@
     ["[0]" product]
     [collection
      ["[0]" list ("[1]#[0]" mix functor monoid)]
-     ["[0]" array {"+" Array} ("[1]#[0]" functor mix)]]]
+     ["[0]" array "_"
+      ["[1]" \\unsafe {"+" Array}]]]]
    [macro
     [syntax {"+" syntax:}]
     ["[0]" code]]
@@ -95,13 +96,13 @@
   (if (n.= 0 level)
     {#Base tail}
     (|> (empty_hierarchy [])
-        (array.write! 0 (path (level_down level) tail))
+        (array.has! 0 (path (level_down level) tail))
         {#Hierarchy})))
 
 (def: (tail singleton)
   (All (_ a) (-> a (Base a)))
   (|> (array.empty 1)
-      (array.write! 0 singleton)))
+      (array.has! 0 singleton)))
 
 (def: (with_tail size level tail parent)
   (All (_ a) (-> Nat Level (Base a) (Hierarchy a) (Hierarchy a)))
@@ -111,41 +112,40 @@
                    ... Just add the tail to it
                    {#Base tail}
                    ... Otherwise, check whether there's a vacant spot
-                   (case (array.read! sub_idx parent)
+                   (if (array.lacks? sub_idx parent)
                      ... If so, set the path to the tail
-                     {.#None}
                      (..path (level_down level) tail)
-                     ... If not, push the tail onto the sub_node.
-                     {.#Some {#Hierarchy sub_node}}
-                     {#Hierarchy (with_tail size (level_down level) tail sub_node)}
+                     (case (array.item sub_idx parent)
+                       ... If not, push the tail onto the sub_node.
+                       {#Hierarchy sub_node}
+                       {#Hierarchy (with_tail size (level_down level) tail sub_node)}
 
-                     _
-                     (undefined))
-                   )]
+                       _
+                       (undefined))))]
     (|> (array.clone parent)
-        (array.write! sub_idx sub_node))))
+        (array.has! sub_idx sub_node))))
 
 (def: (expanded_tail val tail)
   (All (_ a) (-> a (Base a) (Base a)))
   (let [tail_size (array.size tail)]
     (|> (array.empty (++ tail_size))
         (array.copy! tail_size 0 tail 0)
-        (array.write! tail_size val))))
+        (array.has! tail_size val))))
 
 (def: (hierarchy#has level idx val hierarchy)
   (All (_ a) (-> Level Index a (Hierarchy a) (Hierarchy a)))
   (let [sub_idx (branch_idx (i64.right_shifted level idx))]
-    (case (array.read! sub_idx hierarchy)
-      {.#Some {#Hierarchy sub_node}}
+    (case (array.item sub_idx hierarchy)
+      {#Hierarchy sub_node}
       (|> (array.clone hierarchy)
-          (array.write! sub_idx {#Hierarchy (hierarchy#has (level_down level) idx val sub_node)}))
+          (array.has! sub_idx {#Hierarchy (hierarchy#has (level_down level) idx val sub_node)}))
 
-      (^multi {.#Some {#Base base}}
+      (^multi {#Base base}
               (n.= 0 (level_down level)))
       (|> (array.clone hierarchy)
-          (array.write! sub_idx (|> (array.clone base)
-                                    (array.write! (branch_idx idx) val)
-                                    {#Base})))
+          (array.has! sub_idx (|> (array.clone base)
+                                  (array.has! (branch_idx idx) val)
+                                  {#Base})))
 
       _
       (undefined))))
@@ -157,21 +157,21 @@
           {.#None}
 
           (n.> branching_exponent level)
-          (do maybe.monad
-            [base|hierarchy (array.read! sub_idx hierarchy)
-             sub (case base|hierarchy
-                   {#Hierarchy sub}
-                   (without_tail size (level_down level) sub)
-
-                   {#Base _}
-                   (undefined))]
-            (|> (array.clone hierarchy)
-                (array.write! sub_idx {#Hierarchy sub})
-                {.#Some}))
+          (if (array.lacks? sub_idx hierarchy)
+            {.#None}
+            (maybe#each (function (_ sub)
+                          (|> (array.clone hierarchy)
+                              (array.has! sub_idx {#Hierarchy sub})))
+                        (case (array.item sub_idx hierarchy)
+                          {#Hierarchy sub}
+                          (without_tail size (level_down level) sub)
+
+                          {#Base _}
+                          (undefined))))
 
           ... Else...
           (|> (array.clone hierarchy)
-              (array.delete! sub_idx)
+              (array.lacks! sub_idx)
               {.#Some})
           )))
 
@@ -226,8 +226,8 @@
             (|> sequence
                 (with@ #root (|> (`` (: (Hierarchy (~~ (:of val)))
                                         (empty_hierarchy [])))
-                                 (array.write! 0 {#Hierarchy (value@ #root sequence)})
-                                 (array.write! 1 (..path (value@ #level sequence) (value@ #tail sequence)))))
+                                 (array.has! 0 {#Hierarchy (value@ #root sequence)})
+                                 (array.has! 1 (..path (value@ #level sequence) (value@ #tail sequence)))))
                 (revised@ #level level_up))
             ... Otherwise, just push the current tail onto the root.
             (|> sequence
@@ -257,32 +257,30 @@
     (if (n.< (tail_off (value@ #size sequence)) idx)
       (loop [level (value@ #level sequence)
              hierarchy (value@ #root sequence)]
-        (case [(n.> branching_exponent level)
-               (array.read! (branch_idx (i64.right_shifted level idx)) hierarchy)]
-          [#1 {.#Some {#Hierarchy sub}}]
-          (again (level_down level) sub)
-
-          [#0 {.#Some {#Base base}}]
-          {try.#Success base}
-
-          [_ {.#None}]
-          (exception.except ..base_was_not_found [])
-
-          _
-          (exception.except ..incorrect_sequence_structure [])))
+        (let [index (branch_idx (i64.right_shifted level idx))]
+          (if (array.lacks? index hierarchy)
+            (exception.except ..base_was_not_found [])
+            (case [(n.> branching_exponent level)
+                   (array.item index hierarchy)]
+              [#1 {#Hierarchy sub}]
+              (again (level_down level) sub)
+
+              [#0 {#Base base}]
+              {try.#Success base}
+
+              _
+              (exception.except ..incorrect_sequence_structure [])))))
       {try.#Success (value@ #tail sequence)})
     (exception.except ..index_out_of_bounds [sequence idx])))
 
 (def: .public (item idx sequence)
   (All (_ a) (-> Nat (Sequence a) (Try a)))
   (do try.monad
-    [base (base_for idx sequence)]
-    (case (array.read! (branch_idx idx) base)
-      {.#Some value}
-      {try.#Success value}
-      
-      {.#None}
-      (exception.except ..incorrect_sequence_structure []))))
+    [base (base_for idx sequence)
+     .let [index (branch_idx idx)]]
+    (if (array.lacks? index base)
+      (exception.except ..incorrect_sequence_structure [])
+      {try.#Success (array.item index base)})))
 
 (def: .public (has idx val sequence)
   (All (_ a) (-> Nat a (Sequence a) (Try (Sequence a))))
@@ -293,7 +291,7 @@
                                 sequence)
                       (revised@ #tail (`` (: (-> (Base (~~ (:of val)))
                                                  (Base (~~ (:of val))))
-                                             (|>> array.clone (array.write! (branch_idx idx) val))))
+                                             (|>> array.clone (array.has! (branch_idx idx) val))))
                                 sequence))}
       (exception.except ..index_out_of_bounds [sequence idx]))))
 
@@ -327,17 +325,20 @@
                                  (loop [level init_level
                                         root (maybe.else (empty_hierarchy [])
                                                          (without_tail sequence_size init_level (value@ #root sequence)))]
-                                   (if (n.> branching_exponent level)
-                                     (case [(array.read! 1 root) (array.read! 0 root)]
-                                       [{.#None} {.#Some {#Hierarchy sub_node}}]
-                                       (again (level_down level) sub_node)
-
-                                       ... [{.#None} {.#Some {#Base _}}]
-                                       ... (undefined)
-
-                                       _
-                                       [level root])
-                                     [level root])))]]
+                                   (with_expansions [<else> [level root]]
+                                     (if (n.> branching_exponent level)
+                                       (if (array.lacks? 1 root)
+                                         (case (array.item 0 root)
+                                           {#Hierarchy sub_node}
+                                           (again (level_down level) sub_node)
+
+                                           ... {#Base _}
+                                           ... (undefined)
+
+                                           _
+                                           <else>)
+                                         <else>)
+                                       <else>))))]]
          (in (|> sequence
                  (revised@ #size --)
                  (with@ #level level')
@@ -365,26 +366,26 @@
 (syntax: .public (sequence [elems (<>.some <code>.any)])
   (in (.list (` (..of_list (.list (~+ elems)))))))
 
-(implementation: (node_equivalence Equivalence<a>)
+(implementation: (node_equivalence //#=)
   (All (_ a) (-> (Equivalence a) (Equivalence (Node a))))
   
   (def: (= v1 v2)
     (case [v1 v2]
       [{#Base b1} {#Base b2}]
-      (# (array.equivalence Equivalence<a>) = b1 b2)
+      (array.= //#= b1 b2)
       
       [{#Hierarchy h1} {#Hierarchy h2}]
-      (# (array.equivalence (node_equivalence Equivalence<a>)) = h1 h2)
+      (array.= (node_equivalence //#=) h1 h2)
 
       _
       #0)))
 
-(implementation: .public (equivalence Equivalence<a>)
+(implementation: .public (equivalence //#=)
   (All (_ a) (-> (Equivalence a) (Equivalence (Sequence a))))
   
   (def: (= v1 v2)
     (and (n.= (value@ #size v1) (value@ #size v2))
-         (let [(^open "node#[0]") (node_equivalence Equivalence<a>)]
+         (let [(^open "node#[0]") (node_equivalence //#=)]
            (and (node#= {#Base (value@ #tail v1)}
                         {#Base (value@ #tail v2)})
                 (node#= {#Hierarchy (value@ #root v1)}
@@ -393,23 +394,25 @@
 (implementation: node_mix
   (Mix Node)
   
-  (def: (mix f init xs)
+  (def: (mix $ init xs)
     (case xs
       {#Base base}
-      (array#mix f init base)
+      (array.mix (function (_ _ item output) ($ item output))
+                 init
+                 base)
       
       {#Hierarchy hierarchy}
-      (array#mix (function (_ node init') (mix f init' node))
+      (array.mix (function (_ _ node init') (mix $ init' node))
                  init
                  hierarchy))))
 
 (implementation: .public mix
   (Mix Sequence)
   
-  (def: (mix f init xs)
+  (def: (mix $ init xs)
     (let [(^open "[0]") node_mix]
-      (mix f
-           (mix f
+      (mix $
+           (mix $
                 init
                 {#Hierarchy (value@ #root xs)})
            {#Base (value@ #tail xs)}))))
@@ -425,22 +428,24 @@
 (implementation: node_functor
   (Functor Node)
   
-  (def: (each f xs)
+  (def: (each $ xs)
     (case xs
       {#Base base}
-      {#Base (array#each f base)}
+      {#Base (array.each $ base)}
       
       {#Hierarchy hierarchy}
-      {#Hierarchy (array#each (each f) hierarchy)})))
+      {#Hierarchy (array.each (each $) hierarchy)})))
 
 (implementation: .public functor
   (Functor Sequence)
   
-  (def: (each f xs)
+  (def: (each $ xs)
     [#level (value@ #level xs)
      #size (value@ #size xs)
-     #root (|> xs (value@ #root) (array#each (# node_functor each f)))
-     #tail (|> xs (value@ #tail) (array#each f))]))
+     #root (let [... TODO: This binding was established to get around a compilation error. Fix and inline!
+                 $ (# node_functor each $)]
+             (|> xs (value@ #root) (array.each $)))
+     #tail (|> xs (value@ #tail) (array.each $))]))
 
 (implementation: .public apply
   (Apply Sequence)
@@ -518,9 +523,11 @@
 (def: .public (one check items)
   (All (_ a b)
     (-> (-> a (Maybe b)) (Sequence a) (Maybe b)))
-  (case (|> items
-            (value@ #root)
-            (array.one (one|node check)))
+  (case (let [... TODO: This binding was established to get around a compilation error. Fix and inline!
+              check (..one|node check)]
+          (|> items
+              (value@ #root)
+              (array.one check)))
     {.#None}
     (|> items
         (value@ #tail)
diff --git a/stdlib/source/library/lux/math/number/i64.lux b/stdlib/source/library/lux/math/number/i64.lux
index 403ed07f0..281ea025e 100644
--- a/stdlib/source/library/lux/math/number/i64.lux
+++ b/stdlib/source/library/lux/math/number/i64.lux
@@ -128,7 +128,7 @@
 
   (def: &equivalence ..equivalence)
 
-  (def: hash .nat))
+  (def: hash (|>> .nat)))
 
 (template [<monoid> <identity> <composite>]
   [(implementation: .public <monoid>
diff --git a/stdlib/source/library/lux/math/number/int.lux b/stdlib/source/library/lux/math/number/int.lux
index 3967ca6d9..67c640f22 100644
--- a/stdlib/source/library/lux/math/number/int.lux
+++ b/stdlib/source/library/lux/math/number/int.lux
@@ -220,7 +220,7 @@
              (|> repr
                  ("lux text clip" 1 (-- input_size))
                  (# <codec> decoded)
-                 (# try.functor each .int))
+                 (# try.functor each (|>> .int)))
              
              (^ (static ..-sign))
              (|> repr
@@ -242,7 +242,7 @@
   (Hash Int)
   
   (def: &equivalence ..equivalence)
-  (def: hash .nat))
+  (def: hash (|>> .nat)))
 
 (def: .public (right_shifted parameter subject)
   (-> Nat Int Int)
diff --git a/stdlib/source/library/lux/math/number/rev.lux b/stdlib/source/library/lux/math/number/rev.lux
index 959853be7..86a962e88 100644
--- a/stdlib/source/library/lux/math/number/rev.lux
+++ b/stdlib/source/library/lux/math/number/rev.lux
@@ -1,24 +1,24 @@
 (.using
-  [library
-   [lux "*"
-    [abstract
-     [hash {"+" Hash}]
-     [enum {"+" Enum}]
-     [interval {"+" Interval}]
-     [monoid {"+" Monoid}]
-     [equivalence {"+" Equivalence}]
-     [codec {"+" Codec}]
-     [order {"+" Order}]]
-    [control
-     ["[0]" maybe]
-     ["[0]" try]]
-    [data
-     [collection
-      ["[0]" array {"+" Array}]]]]]
-  ["[0]" // "_"
-   ["[1][0]" i64]
-   ["[1][0]" nat]
-   ["[1][0]" int]])
+ [library
+  [lux "*"
+   [abstract
+    [hash {"+" Hash}]
+    [enum {"+" Enum}]
+    [interval {"+" Interval}]
+    [monoid {"+" Monoid}]
+    [equivalence {"+" Equivalence}]
+    [codec {"+" Codec}]
+    [order {"+" Order}]]
+   [control
+    ["[0]" maybe]
+    ["[0]" try]]
+   [data
+    [collection
+     ["[0]" array {"+" Array}]]]]]
+ ["[0]" // "_"
+  ["[1][0]" i64]
+  ["[1][0]" nat]
+  ["[1][0]" int]])
 
 (def: .public /1
   Rev
@@ -186,7 +186,7 @@
   (Hash Rev)
   
   (def: &equivalence ..equivalence)
-  (def: hash .nat))
+  (def: hash (|>> .nat)))
 
 (implementation: .public order
   (Order Rev)
@@ -225,7 +225,7 @@
   ("lux text clip" 1 (-- ("lux text size" input)) input))
 
 (template [<struct> <codec> <char_bit_size> <error>]
-  [(with_expansions [<error_output> (as_is {try.#Failure ("lux text concat" <error> repr)})]
+  [(with_expansions [<failure> (as_is {try.#Failure ("lux text concat" <error> repr)})]
      (implementation: .public <struct>
        (Codec Text Rev)
        
@@ -256,12 +256,12 @@
                  {try.#Success output}
                  {try.#Success (.rev output)}
 
-                 _
-                 <error_output>)
+                 failure
+                 <failure>)
                
-               _
-               <error_output>)
-             <error_output>)))))]
+               else
+               <failure>)
+             <failure>)))))]
 
   [binary //nat.binary 1 "Invalid binary syntax: "]
   [octal  //nat.octal  3 "Invalid octal syntax: "]
diff --git a/stdlib/source/library/lux/math/random.lux b/stdlib/source/library/lux/math/random.lux
index 1b3a9426a..7ae9974a8 100644
--- a/stdlib/source/library/lux/math/random.lux
+++ b/stdlib/source/library/lux/math/random.lux
@@ -126,7 +126,7 @@
 (template [<name> <type> <cast>]
   [(def: .public <name>
      (Random <type>)
-     (# ..functor each <cast> ..i64))]
+     (# ..functor each (|>> <cast>) ..i64))]
 
   [nat Nat .nat]
   [int Int .int]
diff --git a/stdlib/source/library/lux/tool/compiler/language/lux/phase/generation/python/case.lux b/stdlib/source/library/lux/tool/compiler/language/lux/phase/generation/python/case.lux
index 26e21c065..1e285ebb2 100644
--- a/stdlib/source/library/lux/tool/compiler/language/lux/phase/generation/python/case.lux
+++ b/stdlib/source/library/lux/tool/compiler/language/lux/phase/generation/python/case.lux
@@ -25,8 +25,9 @@
     [synthesis
      ["[0]" case]]
     ["/[1]" // "_"
-     ["[1][0]" synthesis {"+" Member Synthesis Path}]
      ["[1][0]" generation]
+     ["[1][0]" synthesis {"+" Synthesis Path}
+      ["[0]" member {"+" Member}]]
      ["//[1]" /// "_"
       [reference
        ["[1][0]" variable {"+" Register}]]
@@ -108,13 +109,11 @@
   (do ///////phase.monad
     [valueO (expression archive valueS)]
     (in (list#mix (function (_ side source)
-                    (.let [method (.case side
-                                    (^template [<side> <accessor>]
-                                      [{<side> lefts}
-                                       (<accessor> (_.int (.int lefts)))])
-                                    ([.#Left //runtime.tuple::left]
-                                     [.#Right //runtime.tuple::right]))]
-                      (method source)))
+                    (.let [method (.if (value@ member.#right? side)
+                                    //runtime.tuple::right
+                                    //runtime.tuple::left)]
+                      (method (_.int (.int (value@ member.#lefts side)))
+                              source)))
                   valueO
                   (list.reversed pathP)))))
 
diff --git a/stdlib/source/library/lux/world/file.lux b/stdlib/source/library/lux/world/file.lux
index d597ee7da..2f1d82a31 100644
--- a/stdlib/source/library/lux/world/file.lux
+++ b/stdlib/source/library/lux/world/file.lux
@@ -581,7 +581,7 @@
 
                      (def: file_size
                        (|>> os/path::getsize
-                            (# (try.with io.monad) each .nat)))
+                            (# (try.with io.monad) each (|>> .nat))))
 
                      (def: last_modified
                        (|>> os/path::getmtime
diff --git a/stdlib/source/poly/lux/data/format/json.lux b/stdlib/source/poly/lux/data/format/json.lux
index 656c94c2a..0985eb5ed 100644
--- a/stdlib/source/poly/lux/data/format/json.lux
+++ b/stdlib/source/poly/lux/data/format/json.lux
@@ -75,7 +75,7 @@
   (def: encoded
     (|>> .nat (# nat_codec encoded)))
   (def: decoded
-    (|>> (# nat_codec decoded) (# try.functor each .int))))
+    (|>> (# nat_codec decoded) (# try.functor each (|>> .int)))))
 
 ... Builds a JSON generator for potentially inexistent values.
 (def: (nullable writer)
diff --git a/stdlib/source/test/lux/control/parser/synthesis.lux b/stdlib/source/test/lux/control/parser/synthesis.lux
index 7ee6a59e6..0a2f2fbeb 100644
--- a/stdlib/source/test/lux/control/parser/synthesis.lux
+++ b/stdlib/source/test/lux/control/parser/synthesis.lux
@@ -1,37 +1,37 @@
 (.using
-  [library
-   [lux "*"
-    ["_" test {"+" Test}]
-    [abstract
-     ["[0]" monad {"+" do}]]
-    [control
-     [pipe {"+" case>}]
-     ["<>" parser]
-     ["[0]" try]
-     ["[0]" exception]]
-    [data
-     ["[0]" bit]
-     ["[0]" text]
-     [collection
-      ["[0]" list ("[1]#[0]" functor)]]]
-    [math
-     ["[0]" random {"+" Random}]
-     [number
-      ["n" nat]
-      ["[0]" i64]
-      ["[0]" frac]]]
-    [meta
-     ["[0]" symbol]]
-    [tool
-     [compiler
-      [reference {"+" }
-       ["[0]" variable {"+" Variable}]]
-      [language
-       [lux
-        [analysis {"+" Environment}]
-        ["[0]" synthesis {"+" Synthesis}]]]]]]]
-  [\\library
-   ["[0]" /]])
+ [library
+  [lux "*"
+   ["_" test {"+" Test}]
+   [abstract
+    ["[0]" monad {"+" do}]]
+   [control
+    [pipe {"+" case>}]
+    ["<>" parser]
+    ["[0]" try]
+    ["[0]" exception]]
+   [data
+    ["[0]" bit]
+    ["[0]" text]
+    [collection
+     ["[0]" list ("[1]#[0]" functor)]]]
+   [math
+    ["[0]" random {"+" Random}]
+    [number
+     ["n" nat]
+     ["[0]" i64]
+     ["[0]" frac]]]
+   [meta
+    ["[0]" symbol]]
+   [tool
+    [compiler
+     [reference {"+" }
+      ["[0]" variable {"+" Variable}]]
+     [language
+      [lux
+       [analysis {"+" Environment}]
+       ["[0]" synthesis {"+" Synthesis}]]]]]]]
+ [\\library
+  ["[0]" /]])
 
 (template: (!expect <pattern> <value>)
   [(case <value>
@@ -80,7 +80,7 @@
                        ))]
 
                 [/.bit /.bit! random.bit synthesis.bit bit.equivalence]
-                [/.i64 /.i64! (# ! each .i64 random.nat) synthesis.i64 i64.equivalence]
+                [/.i64 /.i64! random.i64 synthesis.i64 i64.equivalence]
                 [/.f64 /.f64! random.safe_frac synthesis.f64 frac.equivalence]
                 [/.text /.text! (random.unicode 1) synthesis.text text.equivalence]
                 [/.local /.local! random.nat synthesis.variable/local n.equivalence]
@@ -94,7 +94,7 @@
   ($_ _.and
       (do [! random.monad]
         [expected_bit random.bit
-         expected_i64 (# ! each .i64 random.nat)
+         expected_i64 random.i64
          expected_f64 random.safe_frac
          expected_text (random.unicode 1)]
         (_.cover [/.tuple]
@@ -165,7 +165,7 @@
       (_.for [/.Parser])
       ($_ _.and
           (do [! random.monad]
-            [expected (# ! each (|>> synthesis.i64) random.nat)]
+            [expected (# ! each (|>> synthesis.i64) random.i64)]
             (_.cover [/.result /.any]
                      (|> (/.result /.any (list expected))
                          (!expect (^multi {try.#Success actual}
@@ -175,13 +175,13 @@
                        (!expect (^multi {try.#Failure error}
                                         (exception.match? /.empty_input error)))))
           (do [! random.monad]
-            [expected (# ! each (|>> synthesis.i64) random.nat)]
+            [expected (# ! each (|>> synthesis.i64) random.i64)]
             (_.cover [/.unconsumed_input]
                      (|> (/.result /.any (list expected expected))
                          (!expect (^multi {try.#Failure error}
                                           (exception.match? /.unconsumed_input error))))))
           (do [! random.monad]
-            [dummy (# ! each (|>> synthesis.i64) random.nat)]
+            [dummy (# ! each (|>> synthesis.i64) random.i64)]
             (_.cover [/.end! /.expected_empty_input]
                      (and (|> (/.result /.end! (list))
                               (!expect {try.#Success _}))
@@ -189,7 +189,7 @@
                               (!expect (^multi {try.#Failure error}
                                                (exception.match? /.expected_empty_input error)))))))
           (do [! random.monad]
-            [dummy (# ! each (|>> synthesis.i64) random.nat)]
+            [dummy (# ! each (|>> synthesis.i64) random.i64)]
             (_.cover [/.end?]
                      (and (|> (/.result /.end? (list))
                               (!expect {try.#Success #1}))
diff --git a/stdlib/source/test/lux/data/binary.lux b/stdlib/source/test/lux/data/binary.lux
index e2072944f..d179058fd 100644
--- a/stdlib/source/test/lux/data/binary.lux
+++ b/stdlib/source/test/lux/data/binary.lux
@@ -14,8 +14,9 @@
     ["[0]" exception {"+" Exception}]]
    [data
     [collection
-     [array {"+"}]
-     ["[0]" list ("[1]#[0]" functor)]]]
+     ["[0]" list ("[1]#[0]" functor)]
+     [array
+      [\\unsafe {"+"}]]]]
    [math
     ["[0]" random {"+" Random}]
     [number
diff --git a/stdlib/source/test/lux/data/collection/array.lux b/stdlib/source/test/lux/data/collection/array.lux
index 2eca1688b..b0daba12a 100644
--- a/stdlib/source/test/lux/data/collection/array.lux
+++ b/stdlib/source/test/lux/data/collection/array.lux
@@ -3,14 +3,17 @@
   [lux "*"
    ["_" test {"+" Test}]
    [abstract
+    [functor {"+"}]
     [monad {"+" do}]
+    ["[0]" monoid
+     ["$[1]" \\specification]]
+    ["[0]" mix {"+" Mix}
+     ["$[1]" \\specification]]
     [\\specification
      ["$[0]" equivalence]
-     ["$[0]" monoid]
-     ["$[0]" mix]
      ["$[0]" functor {"+" Injection}]]]
    [control
-    ["[0]" maybe]]
+    ["[0]" maybe ("[1]#[0]" functor)]]
    [data
     ["[0]" bit]
     ["[0]" text ("[1]#[0]" equivalence)]
@@ -22,7 +25,8 @@
     [number
      ["n" nat]]]]]
  [\\library
-  ["[0]" / {"+" Array}]])
+  ["[0]" / {"+" Array}
+   ["!" \\unsafe]]])
 
 (def: injection
   (Injection Array)
@@ -110,6 +114,184 @@
                     (/.any? n.even? the_array)))
         )))
 
+(def: test|unsafe
+  Test
+  (<| (_.covering !._)
+      (_.for [!.Array])
+      (do [! random.monad]
+        [size ..bounded_size
+         base random.nat
+         shift random.nat
+         dummy (random.only (|>> (n.= base) not) random.nat)
+         .let [expected (n.+ base shift)]
+         the_array (random.array size random.nat)
+         evens (random.array size (random.only n.even? random.nat))]
+        (`` ($_ _.and
+                (_.for [!.=]
+                       ($equivalence.spec (function (_ left right)
+                                            (!.= n.equivalence left right))
+                                          (random.array size random.nat)))
+                (_.for [!.composite]
+                       ($monoid.spec (/.equivalence n.equivalence)
+                                     (implementation
+                                      (def: identity (!.empty 0))
+                                      (def: (composite left right)
+                                        (!.composite left right)))
+                                     (random.array size random.nat)))
+                (_.for [!.each]
+                       ($functor.spec ..injection /.equivalence
+                                      (function (_ $ it)
+                                        (!.each $ it))))
+                (_.for [!.mix]
+                       ($mix.spec ..injection /.equivalence
+                                  (: (Mix !.Array)
+                                     (function (_ $ init it)
+                                       (!.mix (function (_ index item output)
+                                                ($ item output))
+                                              init
+                                              it)))))
+                
+                (_.cover [!.empty !.size]
+                         (n.= size (!.size (: (Array Nat)
+                                              (!.empty size)))))
+                (_.cover [!.type]
+                         (case !.Array
+                           (^ (<| {.#Named (symbol !.Array)}
+                                  {.#UnivQ (list)}
+                                  {.#Primitive nominal_type (list {.#Parameter 1})}))
+                           (same? !.type nominal_type)
+
+                           _
+                           false))
+                (_.cover [!.lacks?]
+                         (let [the_array (|> (!.empty 2)
+                                             (: (Array Nat))
+                                             (!.has! 0 expected))]
+                           (and (not (!.lacks? 0 the_array))
+                                (!.lacks? 1 the_array))))
+                (_.cover [!.item !.has!]
+                         (|> (!.empty 2)
+                             (: (Array Nat))
+                             (!.has! 0 expected)
+                             (!.item 0)
+                             (n.= expected)))
+                (_.cover [!.lacks!]
+                         (|> (!.empty 1)
+                             (: (Array Nat))
+                             (!.has! 0 expected)
+                             (!.lacks! 0)
+                             (!.lacks? 0)))
+                (_.cover [!.revised!]
+                         (|> (!.empty 1)
+                             (: (Array Nat))
+                             (!.has! 0 base)
+                             (!.revised! 0 (n.+ shift))
+                             (!.item 0)
+                             (n.= expected)))
+                (_.cover [!.upsert!]
+                         (let [the_array (|> (!.empty 2)
+                                             (: (Array Nat))
+                                             (!.has! 0 base)
+                                             (!.upsert! 0 dummy (n.+ shift))
+                                             (!.upsert! 1 base (n.+ shift)))]
+                           (and (n.= expected (!.item 0 the_array))
+                                (n.= expected (!.item 1 the_array)))))
+                (do !
+                  [occupancy (# ! each (n.% (++ size)) random.nat)]
+                  (_.cover [!.occupancy !.vacancy]
+                           (let [the_array (loop [output (: (Array Nat)
+                                                            (!.empty size))
+                                                  idx 0]
+                                             (if (n.< occupancy idx)
+                                               (again (!.has! idx expected output)
+                                                      (++ idx))
+                                               output))]
+                             (and (n.= occupancy (!.occupancy the_array))
+                                  (n.= size (n.+ (!.occupancy the_array)
+                                                 (!.vacancy the_array)))))))
+                (do !
+                  [the_list (random.list size random.nat)
+                   .let [the_array (!.clone the_array)
+                         members (|> the_array (!.list {.#None}) (set.of_list n.hash))]
+                   default (random.only (function (_ value)
+                                          (not (or (n.even? value)
+                                                   (set.member? members value))))
+                                        random.nat)]
+                  (_.cover [!.of_list !.list]
+                           (and (|> the_list !.of_list (!.list {.#None})
+                                    (# (list.equivalence n.equivalence) = the_list))
+                                (|> the_array (!.list {.#None}) !.of_list
+                                    (!.= n.equivalence the_array))
+                                (exec
+                                  (!.only! n.even? the_array)
+                                  (list.every? (function (_ value)
+                                                 (or (n.even? value)
+                                                     (same? default value)))
+                                               (!.list {.#Some default} the_array))))))
+                (do !
+                  [amount (# ! each (n.% (++ size)) random.nat)]
+                  (_.cover [!.copy!]
+                           (let [copy (: (Array Nat)
+                                         (!.empty size))]
+                             (exec (!.copy! amount 0 the_array 0 copy)
+                               (# (list.equivalence n.equivalence) =
+                                  (list.first amount (!.list {.#None} the_array))
+                                  (!.list {.#None} copy))))))
+                (_.cover [!.clone]
+                         (let [clone (!.clone the_array)]
+                           (and (not (same? the_array clone))
+                                (!.= n.equivalence the_array clone))))
+                (let [the_array (!.clone the_array)
+                      evens (|> the_array (!.list {.#None}) (list.only n.even?))
+                      odds (|> the_array (!.list {.#None}) (list.only n.odd?))]
+                  (_.cover [!.only!]
+                           (exec (!.only! n.even? the_array)
+                             (and (n.= (list.size evens) (!.occupancy the_array))
+                                  (n.= (list.size odds) (!.vacancy the_array))
+                                  (|> the_array
+                                      (!.list {.#None})
+                                      (# (list.equivalence n.equivalence) = evens))))))
+                (let [choose (: (-> Nat (Maybe Text))
+                                (function (_ value)
+                                  (if (n.even? value)
+                                    {.#Some (# n.decimal encoded value)}
+                                    {.#None})))]
+                  (_.cover [!.one]
+                           (|> evens
+                               (!.one choose)
+                               (maybe#each (text#= (|> evens
+                                                       (!.each (# n.decimal encoded))
+                                                       (!.item 0))))
+                               (maybe.else false))))
+                (_.cover [!.example]
+                         (# (maybe.equivalence n.equivalence) =
+                            (!.example n.even? the_array)
+                            (list.example n.even? (!.list {.#None} the_array))))
+                (_.cover [!.example']
+                         (case [(!.example n.even? the_array)
+                                (!.example' (function (_ idx member)
+                                              (n.even? member))
+                                            the_array)]
+                           [{.#Some expected} {.#Some [idx actual]}]
+                           (and (not (!.lacks? idx the_array))
+                                (n.= expected actual)
+                                (n.= actual (!.item idx the_array)))
+
+                           [{.#None} {.#None}]
+                           true
+
+                           _
+                           false))
+                (_.cover [!.every?]
+                         (# bit.equivalence =
+                            (list.every? n.even? (!.list {.#None} the_array))
+                            (!.every? n.even? the_array)))
+                (_.cover [!.any?]
+                         (# bit.equivalence =
+                            (list.any? n.even? (!.list {.#None} the_array))
+                            (!.any? n.even? the_array)))
+                )))))
+
 (def: .public test
   Test
   (<| (_.covering /._)
@@ -130,7 +312,10 @@
                                           (/.empty size)))))
             (_.cover [/.type_name]
                      (case /.Array
-                       (^ {.#Named _ {.#UnivQ _ {.#Primitive nominal_type (list {.#Parameter 1})}}})
+                       (^ (<| {.#Named (symbol /.Array)}
+                              {.#Named (symbol !.Array)}
+                              {.#UnivQ (list)}
+                              {.#Primitive nominal_type (list {.#Parameter 1})}))
                        (same? /.type_name nominal_type)
 
                        _
@@ -163,7 +348,6 @@
                                          (/.write! 0 expected))]
                        (and (/.contains? 0 the_array)
                             (not (/.contains? 1 the_array)))))
-            
             (_.cover [/.update!]
                      (let [the_array (|> (/.empty 1)
                                          (: (Array Nat))
@@ -242,4 +426,6 @@
                          (and (n.= (list.size evens) (/.occupancy the_array))
                               (n.= (list.size odds) (/.vacancy the_array))
                               (|> the_array (/.list {.#None}) (# (list.equivalence n.equivalence) = evens))))))
+
+            ..test|unsafe
             ))))
diff --git a/stdlib/source/test/lux/target/python.lux b/stdlib/source/test/lux/target/python.lux
index 8ff0e74a2..b09be8b72 100644
--- a/stdlib/source/test/lux/target/python.lux
+++ b/stdlib/source/test/lux/target/python.lux
@@ -459,6 +459,7 @@
   (do [! random.monad]
     [$var/0 (# ! each (|>> %.nat (format "v0_") /.var) random.nat)
      $var/1 (# ! each (|>> %.nat (format "v1_") /.var) random.nat)
+     $def (# ! each (|>> %.nat (format "def_") /.var) random.nat)
      expected/0 random.safe_frac
      expected/1 random.safe_frac
      dummy/0 random.safe_frac
@@ -529,6 +530,37 @@
                           (:as Bit)
                           not)
                       ))
+        (_.cover [/.globals/0]
+                 (|> (..statement
+                      (function (_ $output)
+                        ($_ /.then
+                            (/.def $def (list $var/0)
+                                   (/.return (/.in? /.globals/0 (/.string (/.code $var/0)))))
+                            (/.set (list $output) (/.and (/.not (/.in? /.globals/0 (/.string (/.code $var/0))))
+                                                         (/.not (/.apply/* (list (/.float dummy/0)) $def))))
+                            (/.set (list $var/0) (/.float dummy/0))
+                            (/.set (list $output) (/.and $output
+                                                         (/.in? /.globals/0 (/.string (/.code $var/0))))))))
+                     (:as Bit)))
+        (_.cover [/.locals/0]
+                 (|> (..statement
+                      (function (_ $output)
+                        ($_ /.then
+                            (/.def $def (list $var/0)
+                                   (/.return (/.in? /.locals/0 (/.string (/.code $var/0)))))
+                            (/.set (list $output) (/.and (/.not (/.in? /.locals/0 (/.string (/.code $var/0))))
+                                                         (/.apply/* (list (/.float dummy/0)) $def)))
+                            (/.set (list $var/0) (/.float dummy/0))
+                            (/.set (list $output) (/.and $output
+                                                         (/.in? /.locals/0 (/.string (/.code $var/0))))))))
+                     (:as Bit)))
+        (_.cover [/.import]
+                 (|> (..statement
+                      (function (_ $output)
+                        ($_ /.then
+                            (/.import "math")
+                            (/.set (list $output) (/.in? /.globals/0 (/.string "math"))))))
+                     (:as Bit)))
         (_.for [/.Access]
                ..test|access)
         )))
@@ -665,6 +697,23 @@
                                      {.#None}))))
                      (:as Nat)
                      (n.= expected)))
+        (_.cover [/.break]
+                 (|> (..statement
+                      (function (_ $output)
+                        ($_ /.then
+                            (/.set (list $output) (/.int +0))
+                            (/.set (list $iteration) (/.int +0))
+                            (/.while (/.< (/.int (.int (n.+ extra factor))) $iteration)
+                                     ($_ /.then
+                                         (/.set (list $iteration) (/.+ (/.int +1)
+                                                                       $iteration))
+                                         (/.if (/.> (/.int (.int factor)) $iteration)
+                                           /.break
+                                           (/.set (list $output) (/.+ (/.int (.int base))
+                                                                      $output))))
+                                     {.#None}))))
+                     (:as Nat)
+                     (n.= expected)))
         )))
 
 (def: test|statement
@@ -721,6 +770,13 @@
                             (/.set (list $output) (/.apply/* (list) $def)))))
                      (:as Frac)
                      (f.= expected/0)))
+        (_.cover [/.exec]
+                 (|> (..statement
+                      (function (_ $output)
+                        (/.exec {.#Some /.globals/0}
+                          (/.string (/.code (/.set (list $output) (/.float expected/0)))))))
+                     (:as Frac)
+                     (f.= expected/0)))
         ..test|exception
         (_.for [/.Location]
                ..test|location)
diff --git a/stdlib/source/unsafe/lux/data/binary.lux b/stdlib/source/unsafe/lux/data/binary.lux
index 3f542ce73..f5e4d5b4e 100644
--- a/stdlib/source/unsafe/lux/data/binary.lux
+++ b/stdlib/source/unsafe/lux/data/binary.lux
@@ -8,7 +8,8 @@
      [inline {"+" inline:}]]]
    [data
     [collection
-     ["[0]" array]]]
+     ["[0]" array "_"
+      ["[1]" \\unsafe]]]]
    [math
     [number {"+" hex}
      ["[0]" i64]]]]])
@@ -53,273 +54,271 @@
        (type: .public Binary
          (array.Array (I64 Any)))))
 
-(with_expansions [<size> (: Nat size)
-                  <jvm> (ffi.array byte <size>)
-                  <jvm> (: ..Binary <jvm>)]
-  (template: .public (empty size)
-    [(: ..Binary
-        (for [@.old <jvm>
-              @.jvm <jvm>
-
-              @.js
-              (|> <size>
-                  .int
-                  "lux i64 f64"
-                  []
-                  ("js object new" ("js constant" "ArrayBuffer"))
-                  []
-                  ("js object new" ("js constant" "Uint8Array"))
-                  (:as ..Binary))
-
-              @.python
-              (|> <size>
-                  ("python apply" (:as ffi.Function ("python constant" "bytearray")))
-                  (:as ..Binary))
-
-              @.scheme
-              (..make-bytevector <size>)]
-
-             ... Default
-             (array.empty <size>)))]))
-
-(with_expansions [<it> (: ..Binary it)
-                  <jvm> (ffi.length <it>)]
-  (template: .public (size it)
-    [(: Nat
-        (for [@.old <jvm>
-              @.jvm <jvm>
-
-              @.js
-              (|> <it>
-                  ("js object get" "length")
-                  (:as Frac)
-                  "lux f64 i64"
-                  .nat)
-
-              @.python
-              (|> <it>
-                  (:as (array.Array (I64 Any)))
-                  "python array length")
-
-              @.scheme
-              (..bytevector-length [<it>])]
-
-             ... Default
-             (array.size <it>)))]))
+(`` (with_expansions [<size> (.: .Nat size)
+                      <jvm> (ffi.array byte <size>)
+                      <jvm> (.: ..Binary <jvm>)]
+      (template: .public (empty size)
+        [(: ..Binary
+            (for [(~~ (.static @.old)) <jvm>
+                  (~~ (.static @.jvm)) <jvm>
+
+                  (~~ (.static @.js))
+                  (.|> <size>
+                       .int
+                       "lux i64 f64"
+                       []
+                       ("js object new" ("js constant" "ArrayBuffer"))
+                       []
+                       ("js object new" ("js constant" "Uint8Array"))
+                       (.:as ..Binary))
+
+                  (~~ (.static @.python))
+                  (.|> <size>
+                       ("python apply" (.:as ffi.Function ("python constant" "bytearray")))
+                       (.:as ..Binary))
+
+                  (~~ (.static @.scheme))
+                  (..make-bytevector <size>)]
+
+                 ... Default
+                 (array.empty <size>)))])))
+
+(`` (with_expansions [<it> (.: ..Binary it)
+                      <jvm> (ffi.length <it>)]
+      (template: .public (size it)
+        [(.: .Nat
+             (.for [(~~ (.static @.old)) <jvm>
+                    (~~ (.static @.jvm)) <jvm>
+
+                    (~~ (.static @.js))
+                    (.|> <it>
+                         ("js object get" "length")
+                         (.:as .Frac)
+                         "lux f64 i64"
+                         .nat)
+
+                    (~~ (.static @.python))
+                    (.|> <it>
+                         (.:as (array.Array (.I64 .Any)))
+                         "python array length")
+
+                    (~~ (.static @.scheme))
+                    (..bytevector-length [<it>])]
+
+                   ... Default
+                   (array.size <it>)))])))
 
 (def: byte_mask
   Nat
   (i64.mask i64.bits_per_byte))
 
 (with_expansions [<byte_mask> (.static ..byte_mask)
-                  <it> (: ..Binary it)
-                  <index> (: Nat index)
+                  <it> (.: ..Binary it)
+                  <index> (.: .Nat index)
                   <jvm> (ffi.read! <index> <it>)
                   <jvm> (ffi.byte_to_long <jvm>)
-                  <jvm> (|> <jvm>
-                            (:as I64)
-                            ("lux i64 and" <byte_mask>))]
+                  <jvm> (.|> <jvm>
+                             (.:as .I64)
+                             ("lux i64 and" <byte_mask>))]
   (template: .public (bytes/1 index it)
-    [(<| (:as .I64)
-         (: (.I64 .Any))
-         (`` (for [@.old (~~ <jvm>)
-                   @.jvm (~~ <jvm>)
-
-                   @.js
-                   (|> <it>
-                       (:as (array.Array .Frac))
-                       ("js array read" <index>)
-                       "lux f64 i64"
-                       .i64)
-
-                   @.python
-                   (|> <it>
-                       (:as (array.Array .I64))
-                       ("python array read" <index>))
-
-                   @.scheme
-                   (..bytevector-u8-ref [<it> <index>])]
-
-                  ... Default
-                  (.case (array.read! <index> <it>)
-                    {.#Some it}
-                    it
-
-                    {.#None}
-                    (.i64 (: (I64 Any) 0))))))]))
+    [(.<| (.:as .I64)
+          (.: (.I64 .Any))
+          (`` (.for [(~~ (.static @.old)) (~~ <jvm>)
+                     (~~ (.static @.jvm)) (~~ <jvm>)
+
+                     (~~ (.static @.js))
+                     (.|> <it>
+                          (.:as (array.Array .Frac))
+                          ("js array read" <index>)
+                          "lux f64 i64"
+                          .i64)
+
+                     (~~ (.static @.python))
+                     (.|> <it>
+                          (.:as (array.Array .I64))
+                          ("python array read" <index>))
+
+                     (~~ (.static @.scheme))
+                     (..bytevector-u8-ref [<it> <index>])]
+
+                    ... Default
+                    (.if (array.lacks? <index> <it>)
+                      (.i64 0)
+                      (array.item <index> <it>)))))]))
 
 (template: .public (bytes/2 index' it')
-  [(<| (let [index (: Nat index')
-             it (: ..Binary it')])
-       (:as .I64)
-       (: (.I64 .Any))
-       ($_ "lux i64 or"
-           ("lux i64 left-shift" 8 (..bytes/1 index it))
-           (..bytes/1 ("lux i64 +" 1 index) it)))])
+  [(.<| (.let [index (.: Nat index')
+               it (.: ..Binary it')])
+        (.:as .I64)
+        (.: (.I64 .Any))
+        (.$_ "lux i64 or"
+             ("lux i64 left-shift" 8 (..bytes/1 index it))
+             (..bytes/1 ("lux i64 +" 1 index) it)))])
 
 (template: .public (bytes/4 index' it')
-  [(<| (let [index (: Nat index')
-             it (: ..Binary it')])
-       (:as .I64)
-       (: (.I64 .Any))
-       ($_ "lux i64 or"
-           ("lux i64 left-shift" 24 (..bytes/1 index it))
-           ("lux i64 left-shift" 16 (..bytes/1 ("lux i64 +" 1 index) it))
-           ("lux i64 left-shift" 8 (..bytes/1 ("lux i64 +" 2 index) it))
-           (..bytes/1 ("lux i64 +" 3 index) it)))])
+  [(.<| (.let [index (.: Nat index')
+               it (.: ..Binary it')])
+        (.:as .I64)
+        (.: (.I64 .Any))
+        (.$_ "lux i64 or"
+             ("lux i64 left-shift" 24 (..bytes/1 index it))
+             ("lux i64 left-shift" 16 (..bytes/1 ("lux i64 +" 1 index) it))
+             ("lux i64 left-shift" 8 (..bytes/1 ("lux i64 +" 2 index) it))
+             (..bytes/1 ("lux i64 +" 3 index) it)))])
 
 (template: .public (bytes/8 index' it')
-  [(<| (let [index (: Nat index')
-             it (: ..Binary it')])
-       (:as .I64)
-       (: (.I64 .Any))
-       ($_ "lux i64 or"
-           ("lux i64 left-shift" 56 (..bytes/1 index it))
-           ("lux i64 left-shift" 48 (..bytes/1 ("lux i64 +" 1 index) it))
-           ("lux i64 left-shift" 40 (..bytes/1 ("lux i64 +" 2 index) it))
-           ("lux i64 left-shift" 32 (..bytes/1 ("lux i64 +" 3 index) it))
-           ("lux i64 left-shift" 24 (..bytes/1 ("lux i64 +" 4 index) it))
-           ("lux i64 left-shift" 16 (..bytes/1 ("lux i64 +" 5 index) it))
-           ("lux i64 left-shift" 8 (..bytes/1 ("lux i64 +" 6 index) it))
-           (..bytes/1 ("lux i64 +" 7 index) it)))])
+  [(.<| (.let [index (.: Nat index')
+               it (.: ..Binary it')])
+        (.:as .I64)
+        (.: (.I64 .Any))
+        (.$_ "lux i64 or"
+             ("lux i64 left-shift" 56 (..bytes/1 index it))
+             ("lux i64 left-shift" 48 (..bytes/1 ("lux i64 +" 1 index) it))
+             ("lux i64 left-shift" 40 (..bytes/1 ("lux i64 +" 2 index) it))
+             ("lux i64 left-shift" 32 (..bytes/1 ("lux i64 +" 3 index) it))
+             ("lux i64 left-shift" 24 (..bytes/1 ("lux i64 +" 4 index) it))
+             ("lux i64 left-shift" 16 (..bytes/1 ("lux i64 +" 5 index) it))
+             ("lux i64 left-shift" 8 (..bytes/1 ("lux i64 +" 6 index) it))
+             (..bytes/1 ("lux i64 +" 7 index) it)))])
 
 (with_expansions [<byte> (hex "FF")
-                  <it> (: ..Binary it)
-                  <index> (: Nat index)
-                  <value> (: (I64 Any) value)
-                  <jvm_value> (for [@.old
-                                    (:as Int <value>)
-
-                                    @.jvm
-                                    (:as (Primitive "java.lang.Long") <value>)]
-                                   <value>)
+                  <it> (.: ..Binary it)
+                  <index> (.: .Nat index)
+                  <value> (.: (.I64 .Any) value)
+                  <jvm_value> (`` (.for [(~~ (.static @.old))
+                                         (.:as .Int <value>)
+
+                                         (~~ (.static @.jvm))
+                                         (.:as (.Primitive "java.lang.Long") <value>)]
+                                        <value>))
+                  <jvm_value> <jvm_value>
                   <jvm_value> (ffi.long_to_byte <jvm_value>)
                   <jvm> (ffi.write! <index> <jvm_value> <it>)]
-  (template: .public (with/1! index value it)
-    [(: ..Binary
-        (for [@.old <jvm>
-              @.jvm <jvm>
-
-              @.js
-              (|> <it>
-                  (: ..Binary)
-                  (:as (array.Array .Frac))
-                  ("js array write" <index>
-                   (|> <value>
-                       .int
-                       ("lux i64 and" (.int <byte>))
-                       "lux i64 f64"))
-                  (:as ..Binary))
-              
-              @.python
-              (|> <it>
-                  (: ..Binary)
-                  (:as (array.Array (I64 Any)))
-                  ("python array write" <index> (|> <value> ("lux i64 and" <byte>) (: (I64 Any))))
-                  (:as ..Binary))
-              
-              @.scheme
-              (let [it' <it>]
-                (exec
-                  (..bytevector-u8-set! [it' <index> <value>])
-                  it'))]
-
-             ... Default
-             (array.write! <index> (|> <value> .int ("lux i64 and" (.int <byte>))) <it>)))]))
+  (`` (template: .public (with/1! index value it)
+        [(.: ..Binary
+             (.for [(~~ (.static @.old)) <jvm>
+                    (~~ (.static @.jvm)) <jvm>
+
+                    (~~ (.static @.js))
+                    (.|> <it>
+                         (.: ..Binary)
+                         (.:as (array.Array .Frac))
+                         ("js array write" <index>
+                          (.|> <value>
+                               .int
+                               ("lux i64 and" (.int <byte>))
+                               "lux i64 f64"))
+                         (.:as ..Binary))
+                    
+                    (~~ (.static @.python))
+                    (.|> <it>
+                         (.: ..Binary)
+                         (.:as (array.Array (.I64 .Any)))
+                         ("python array write" <index> (.|> <value> ("lux i64 and" <byte>) (.: (.I64 .Any))))
+                         (.:as ..Binary))
+                    
+                    (~~ (.static @.scheme))
+                    (.let [it' <it>]
+                      (.exec
+                        (..bytevector-u8-set! [it' <index> <value>])
+                        it'))]
+
+                   ... Default
+                   (array.has! <index> (.|> <value> .int ("lux i64 and" (.int <byte>))) <it>)))])))
 
 (template: .public (with/2! index' value' it)
-  [(let [index (: Nat index')
-         value (: (I64 Any) value')]
-     (|> it
-         (..with/1! index ("lux i64 right-shift" 8 value))
-         (..with/1! ("lux i64 +" 1 index) value)))])
+  [(.let [index (.: .Nat index')
+          value (.: (.I64 .Any) value')]
+     (.|> it
+          (..with/1! index ("lux i64 right-shift" 8 value))
+          (..with/1! ("lux i64 +" 1 index) value)))])
 
 (template: .public (with/4! index' value' it)
-  [(let [index (: Nat index')
-         value (: (I64 Any) value')]
-     (|> it
-         (..with/1! index ("lux i64 right-shift" 24 value))
-         (..with/1! ("lux i64 +" 1 index) ("lux i64 right-shift" 16 value))
-         (..with/1! ("lux i64 +" 2 index) ("lux i64 right-shift" 8 value))
-         (..with/1! ("lux i64 +" 3 index) value)))])
-
-(template: .public (with/8! index' value' it)
-  [(let [index (: Nat index')
-         value (: (I64 Any) value')]
-     (for [@.scheme (let [write_high (: (-> ..Binary ..Binary)
-                                        (|>> (..with/1! index ("lux i64 right-shift" 56 value))
-                                             (..with/1! ("lux i64 +" 1 index) ("lux i64 right-shift" 48 value))
-                                             (..with/1! ("lux i64 +" 2 index) ("lux i64 right-shift" 40 value))
-                                             (..with/1! ("lux i64 +" 3 index) ("lux i64 right-shift" 32 value))))
-                          write_low (: (-> ..Binary ..Binary)
-                                       (|>> (..with/1! ("lux i64 +" 4 index) ("lux i64 right-shift" 24 value))
-                                            (..with/1! ("lux i64 +" 5 index) ("lux i64 right-shift" 16 value))
-                                            (..with/1! ("lux i64 +" 6 index) ("lux i64 right-shift" 8 value))
-                                            (..with/1! ("lux i64 +" 7 index) value)))]
-                      (|> it
-                          write_high
-                          write_low))]
-          (|> it
-              (..with/1! index ("lux i64 right-shift" 56 value))
-              (..with/1! ("lux i64 +" 1 index) ("lux i64 right-shift" 48 value))
-              (..with/1! ("lux i64 +" 2 index) ("lux i64 right-shift" 40 value))
-              (..with/1! ("lux i64 +" 3 index) ("lux i64 right-shift" 32 value))
-              (..with/1! ("lux i64 +" 4 index) ("lux i64 right-shift" 24 value))
-              (..with/1! ("lux i64 +" 5 index) ("lux i64 right-shift" 16 value))
-              (..with/1! ("lux i64 +" 6 index) ("lux i64 right-shift" 8 value))
-              (..with/1! ("lux i64 +" 7 index) value))))])
-
-(with_expansions [<reference> (: ..Binary reference')
-                  <sample> (: ..Binary sample')
+  [(.let [index (.: .Nat index')
+          value (.: (.I64 .Any) value')]
+     (.|> it
+          (..with/1! index ("lux i64 right-shift" 24 value))
+          (..with/1! ("lux i64 +" 1 index) ("lux i64 right-shift" 16 value))
+          (..with/1! ("lux i64 +" 2 index) ("lux i64 right-shift" 8 value))
+          (..with/1! ("lux i64 +" 3 index) value)))])
+
+(`` (template: .public (with/8! index' value' it)
+      [(.let [index (.: .Nat index')
+              value (.: (.I64 .Any) value')]
+         (.for [(~~ (.static @.scheme)) (.let [write_high (.: (.-> ..Binary ..Binary)
+                                                              (.|>> (..with/1! index ("lux i64 right-shift" 56 value))
+                                                                    (..with/1! ("lux i64 +" 1 index) ("lux i64 right-shift" 48 value))
+                                                                    (..with/1! ("lux i64 +" 2 index) ("lux i64 right-shift" 40 value))
+                                                                    (..with/1! ("lux i64 +" 3 index) ("lux i64 right-shift" 32 value))))
+                                               write_low (.: (.-> ..Binary ..Binary)
+                                                             (.|>> (..with/1! ("lux i64 +" 4 index) ("lux i64 right-shift" 24 value))
+                                                                   (..with/1! ("lux i64 +" 5 index) ("lux i64 right-shift" 16 value))
+                                                                   (..with/1! ("lux i64 +" 6 index) ("lux i64 right-shift" 8 value))
+                                                                   (..with/1! ("lux i64 +" 7 index) value)))]
+                                          (.|> it
+                                               write_high
+                                               write_low))]
+               (.|> it
+                    (..with/1! index ("lux i64 right-shift" 56 value))
+                    (..with/1! ("lux i64 +" 1 index) ("lux i64 right-shift" 48 value))
+                    (..with/1! ("lux i64 +" 2 index) ("lux i64 right-shift" 40 value))
+                    (..with/1! ("lux i64 +" 3 index) ("lux i64 right-shift" 32 value))
+                    (..with/1! ("lux i64 +" 4 index) ("lux i64 right-shift" 24 value))
+                    (..with/1! ("lux i64 +" 5 index) ("lux i64 right-shift" 16 value))
+                    (..with/1! ("lux i64 +" 6 index) ("lux i64 right-shift" 8 value))
+                    (..with/1! ("lux i64 +" 7 index) value))))]))
+
+(with_expansions [<reference> (.: ..Binary reference')
+                  <sample> (.: ..Binary sample')
                   <jvm> (java/util/Arrays::equals <reference> <sample>)
                   <jvm> (ffi.of_boolean <jvm>)]
-  (template: .public (= reference' sample')
-    [(for [@.old <jvm>
-           @.jvm <jvm>]
-          (let [reference <reference>
-                sample <sample>
-                limit (..size reference)]
-            (and ("lux i64 =" limit (..size sample))
-                 (loop [index 0]
-                   (if ("lux i64 =" limit index)
-                     true
-                     (and ("lux i64 ="
-                           (..bytes/1 index reference)
-                           (..bytes/1 index sample))
-                          (again (++ index))))))))]))
+  (`` (template: .public (= reference' sample')
+        [(.for [(~~ (.static @.old)) <jvm>
+                (~~ (.static @.jvm)) <jvm>]
+               (.let [reference <reference>
+                      sample <sample>
+                      limit (..size reference)]
+                 (.and ("lux i64 =" limit (..size sample))
+                       (.loop [index 0]
+                         (.if ("lux i64 =" limit index)
+                           .true
+                           (.and ("lux i64 ="
+                                  (..bytes/1 index reference)
+                                  (..bytes/1 index sample))
+                                 (again ("lux i64 +" 1 index))))))))])))
 
 ... TODO: Turn into a template ASAP.
-(inline: .public (copy! bytes source_offset source target_offset target)
-  (-> Nat Nat ..Binary Nat ..Binary ..Binary)
-  (with_expansions [<jvm> (java/lang/System::arraycopy source (ffi.as_int (.int source_offset))
-                                                       target (ffi.as_int (.int target_offset))
-                                                       (ffi.as_int (.int bytes)))
-                    <jvm> (exec
-                            <jvm>
-                            target)]
-    (for [@.old <jvm>
-          @.jvm <jvm>]
-         
-         ... Default
-         (loop [index 0]
-           (if ("lux i64 <" (.int bytes) (.int index))
-             (exec
-               (..with/1! ("lux i64 +" target_offset index)
-                          (..bytes/1 ("lux i64 +" source_offset index) source)
-                          target)
-               (again (++ index)))
-             target)))))
+(`` (inline: .public (copy! bytes source_offset source target_offset target)
+      (-> .Nat .Nat ..Binary Nat ..Binary ..Binary)
+      (with_expansions [<jvm> (java/lang/System::arraycopy source (ffi.as_int (.int source_offset))
+                                                           target (ffi.as_int (.int target_offset))
+                                                           (ffi.as_int (.int bytes)))
+                        <jvm> (.exec
+                                <jvm>
+                                target)]
+        (.for [(~~ (.static @.old)) <jvm>
+               (~~ (.static @.jvm)) <jvm>]
+              
+              ... Default
+              (.loop [index 0]
+                (.if ("lux i64 <" (.int bytes) (.int index))
+                  (.exec
+                    (..with/1! ("lux i64 +" target_offset index)
+                               (..bytes/1 ("lux i64 +" source_offset index) source)
+                               target)
+                    (again ("lux i64 +" 1 index)))
+                  target))))))
 
 ... TODO: Turn into a template ASAP.
-(with_expansions [<jvm> (java/util/Arrays::copyOfRange binary
-                                                       (ffi.as_int (.int offset))
-                                                       (ffi.as_int (.int limit)))
-                  <jvm> (let [limit ("lux i64 +" size offset)]
-                          <jvm>)]
-  (inline: .public (slice offset size binary)
-    (-> Nat Nat ..Binary ..Binary)
-    (for [@.old <jvm>
-          @.jvm <jvm>]
-         
-         ... Default
-         (..copy! size offset binary 0 (..empty size)))))
+(`` (with_expansions [<jvm> (java/util/Arrays::copyOfRange binary
+                                                           (ffi.as_int (.int offset))
+                                                           (ffi.as_int (.int limit)))
+                      <jvm> (.let [limit ("lux i64 +" size offset)]
+                              <jvm>)]
+      (inline: .public (slice offset size binary)
+        (-> .Nat .Nat ..Binary ..Binary)
+        (.for [(~~ (.static @.old)) <jvm>
+               (~~ (.static @.jvm)) <jvm>]
+              
+              ... Default
+              (..copy! size offset binary 0 (..empty size))))))
diff --git a/stdlib/source/unsafe/lux/data/collection/array.lux b/stdlib/source/unsafe/lux/data/collection/array.lux
new file mode 100644
index 000000000..cd6bebf63
--- /dev/null
+++ b/stdlib/source/unsafe/lux/data/collection/array.lux
@@ -0,0 +1,409 @@
+(.using
+ [library
+  [lux {"-" type list}
+   ["@" target]
+   [abstract
+    ["[0]" functor]]
+   [data
+    [collection
+     ["[0]" list]]]]])
+
+(def: .public type
+  "#Array")
+
+(type: .public (Array a)
+  {.#Primitive ..type {.#Item a {.#End}}})
+
+(with_expansions [<index_type> (.Primitive "java.lang.Long")
+                  <elem_type> (.Primitive "java.lang.Object")
+                  <array_type> (.type (..Array <elem_type>))]
+  (for [@.jvm
+        (template: (int! value)
+          [(.|> value
+                (.:as <index_type>)
+                "jvm object cast"
+                "jvm conversion long-to-int")])]
+       (as_is))
+  
+  (`` (template: .public (empty <size>)
+        [((.: (.All (_ a) (.-> .Nat (..Array a)))
+              (.function (empty size)
+                (.for [(~~ (.static @.old))
+                       (.:expected ("jvm anewarray" "(java.lang.Object )" size))
+
+                       (~~ (.static @.jvm))
+                       (|> (~~ (..int! size))
+                           "jvm array new object"
+                           (.: <array_type>)
+                           .:expected)
+
+                       (~~ (.static @.js)) ("js array new" size)
+                       (~~ (.static @.python)) ("python array new" size)
+                       (~~ (.static @.lua)) ("lua array new" size)
+                       (~~ (.static @.ruby)) ("ruby array new" size)
+                       (~~ (.static @.php)) ("php array new" size)
+                       (~~ (.static @.scheme)) ("scheme array new" size)])))
+          <size>)]))
+
+  (`` (template: .public (size <array>)
+        [((.: (.All (_ a) (.-> (..Array a) .Nat))
+              (.function (size array)
+                (.for [(~~ (.static @.old))
+                       ("jvm arraylength" array)
+
+                       (~~ (.static @.jvm))
+                       (.|> array
+                            (.:as <array_type>)
+                            "jvm array length object"
+                            "jvm conversion int-to-long"
+                            "jvm object cast"
+                            (.: <index_type>)
+                            (.:as .Nat))
+
+                       (~~ (.static @.js)) ("js array length" array)
+                       (~~ (.static @.python)) ("python array length" array)
+                       (~~ (.static @.lua)) ("lua array length" array)
+                       (~~ (.static @.ruby)) ("ruby array length" array)
+                       (~~ (.static @.php)) ("php array length" array)
+                       (~~ (.static @.scheme)) ("scheme array length" array)])))
+          <array>)]))
+
+  (template: (lacks?' <read!> <null?> index array)
+    [(<null?> (<read!> index array))])
+
+  (`` (template: .public (lacks? <index> <array>)
+        [((.: (.All (_ a)
+                (.-> .Nat (..Array a) .Bit))
+              (.function (lacks? index array)
+                (.let [size (..size array)]
+                  (.if ("lux i64 <" (.int size) (.int index))
+                    (.for [(~~ (.static @.old))
+                           ("jvm object null?" ("jvm aaload" array index))
+
+                           (~~ (.static @.jvm))
+                           (.|> array
+                                (.:as <array_type>)
+                                ("jvm array read object" (~~ (int! index)))
+                                "jvm object null?")
+
+                           (~~ (.static @.js)) (~~ (lacks?' "js array read" "js object undefined?" index array))
+                           (~~ (.static @.python)) (~~ (lacks?' "python array read" "python object none?" index array))
+                           (~~ (.static @.lua)) (~~ (lacks?' "lua array read" "lua object nil?" index array))
+                           (~~ (.static @.ruby)) (~~ (lacks?' "ruby array read" "ruby object nil?" index array))
+                           (~~ (.static @.php)) (~~ (lacks?' "php array read" "php object null?" index array))
+                           (~~ (.static @.scheme)) (~~ (lacks?' "scheme array read" "scheme object nil?" index array))])
+                    .true))))
+          <index> <array>)]))
+
+  (`` (template: .public (item <index> <array>)
+        [((.: (.All (_ a)
+                (.-> .Nat (..Array a) a))
+              (.function (item index array)
+                (.for [(~~ (.static @.old))
+                       ("jvm aaload" array index)
+
+                       (~~ (.static @.jvm))
+                       (.|> array
+                            (.:as <array_type>)
+                            ("jvm array read object" (~~ (int! index)))
+                            .:expected)
+
+                       (~~ (.static @.js)) ("js array read" index array)
+                       (~~ (.static @.python)) ("python array read" index array)
+                       (~~ (.static @.lua)) ("lua array read" index array)
+                       (~~ (.static @.ruby)) ("ruby array read" index array)
+                       (~~ (.static @.php)) ("php array read" index array)
+                       (~~ (.static @.scheme)) ("scheme array read" index array)])))
+          <index> <array>)]))
+
+  (`` (template: .public (has! <index> <value> <array>)
+        [((.: (.All (_ a)
+                (.-> .Nat a (..Array a) (..Array a)))
+              (.function (has! index value array)
+                (.for [(~~ (.static @.old))
+                       ("jvm aastore" array index value)
+
+                       (~~ (.static @.jvm))
+                       (.|> array
+                            (.:as <array_type>)
+                            ("jvm array write object" (~~ (int! index)) (.:as <elem_type> value))
+                            .:expected)
+
+                       (~~ (.static @.js)) ("js array write" index value array)
+                       (~~ (.static @.python)) ("python array write" index value array)
+                       (~~ (.static @.lua)) ("lua array write" index value array)
+                       (~~ (.static @.ruby)) ("ruby array write" index value array)
+                       (~~ (.static @.php)) ("php array write" index value array)
+                       (~~ (.static @.scheme)) ("scheme array write" index value array)])))
+          <index> <value> <array>)]))
+
+  (`` (template: .public (lacks! <index> <array>)
+        [((.: (.All (_ a)
+                (.-> .Nat (..Array a) (..Array a)))
+              (.function (lacks! index array)
+                (.let [size (..size array)]
+                  (.if ("lux i64 <" (.int size) (.int index))
+                    (.for [(~~ (.static @.old))
+                           (..has! index (.:expected ("jvm object null")) array)
+                           
+                           (~~ (.static @.jvm))
+                           (..has! index (.:expected (: <elem_type> ("jvm object null"))) array)
+
+                           (~~ (.static @.js)) ("js array delete" index array)
+                           (~~ (.static @.python)) ("python array delete" index array)
+                           (~~ (.static @.lua)) ("lua array delete" index array)
+                           (~~ (.static @.ruby)) ("ruby array delete" index array)
+                           (~~ (.static @.php)) ("php array delete" index array)
+                           (~~ (.static @.scheme)) ("scheme array delete" index array)])
+                    array))))
+          <index> <array>)]))
+  )
+
+(template: .public (revised! <index> <$> <array>)
+  [((.: (.All (_ a)
+          (.-> .Nat (.-> a a) (..Array a) (..Array a)))
+        (.function (revised! index $ array)
+          (.if (..lacks? index array)
+            array
+            (..has! index ($ (..item index array)) array))))
+    <index> <$> <array>)])
+
+(template: .public (upsert! <index> <default> <$> <array>)
+  [((.: (.All (_ a)
+          (.-> .Nat a (.-> a a) (..Array a) (..Array a)))
+        (.function (upsert! index default $ array)
+          (..has! index
+                  ($ (.if (..lacks? index array)
+                       default
+                       (..item index array)))
+                  array)))
+    <index> <default> <$> <array>)])
+
+(template: .public (copy! <length> <src_start> <src_array> <dest_start> <dest_array>)
+  [((.: (.All (_ a)
+          (.-> .Nat .Nat (..Array a) .Nat (..Array a)
+               (..Array a)))
+        (.function (copy! length src_start src_array dest_start dest_array)
+          (.loop [offset 0]
+            (.if ("lux i64 <" (.int length) (.int offset))
+              (.exec
+                (.if (..lacks? ("lux i64 +" offset src_start) src_array)
+                  (..lacks! ("lux i64 +" offset dest_start) dest_array)
+                  (..has! ("lux i64 +" offset dest_start)
+                          (..item ("lux i64 +" offset src_start) src_array)
+                          dest_array))
+                (again ("lux i64 +" 1 offset)))
+              dest_array))))
+    <length> <src_start> <src_array> <dest_start> <dest_array>)])
+
+(template [<name> <when_lacks> <when_has>]
+  [(template: .public (<name> <array>)
+     [((.: (.All (_ a) (.-> (..Array a) .Nat))
+           (.function (occupancy array)
+             (.let [size (..size array)]
+               (.loop [index 0
+                       it 0]
+                 (.if ("lux i64 <" (.int size) (.int index))
+                   (.if (..lacks? index array)
+                     (again ("lux i64 +" 1 index) <when_lacks>)
+                     (again ("lux i64 +" 1 index) <when_has>))
+                   it)))))
+       <array>)])]
+
+  [occupancy it ("lux i64 +" 1 it)]
+  [vacancy ("lux i64 +" 1 it) it]
+  )
+
+(template: .public (only! <?> <it>)
+  [((.: (.All (_ a)
+          (.-> (.-> a .Bit) (..Array a) (..Array a)))
+        (.function (only! ? it)
+          (.let [size (..size it)]
+            (.loop [index 0]
+              (.if ("lux i64 <" (.int size) (.int index))
+                (.exec
+                  (.if (..lacks? index it)
+                    it
+                    (.if (? (..item index it))
+                      it
+                      (..lacks! index it)))
+                  (again ("lux i64 +" 1 index)))
+                it)))))
+    <?> <it>)])
+
+(template [<name> <predicate> <test> <type> <term>]
+  [(template: .public (<name> <?> <it>)
+     [((.: (.All (_ a)
+             (.-> <predicate> (..Array a) (.Maybe <type>)))
+           (.function (<name> ? it)
+             (.let [size (..size it)]
+               (.loop [index 0]
+                 (.if ("lux i64 <" (.int size) (.int index))
+                   (.if (..lacks? index it)
+                     (again ("lux i64 +" 1 index))
+                     (.let [it (..item index it)]
+                       (.if <test>
+                         {.#Some <term>}
+                         (again ("lux i64 +" 1 index)))))
+                   {.#None})))))
+       <?> <it>)])]
+
+  [example (.-> a .Bit) (? it) a it]
+  [example' (.-> Nat a .Bit) (? index it) [Nat a] [index it]]
+  )
+
+(template: .public (clone <it>)
+  [((.: (.All (_ a) (.-> (..Array a) (..Array a)))
+        (.function (clone it)
+          (.let [size (..size it)]
+            (..copy! size 0 it 0 (..empty size)))))
+    <it>)])
+
+(template: .public (of_list <input>)
+  [((.: (.All (_ a) (.-> (.List a) (..Array a)))
+        (.function (of_list input)
+          (.let [size (list.size input)
+                 output (..empty size)]
+            (.loop [index 0
+                    input input]
+              (.case input
+                {.#End}
+                output
+                
+                {.#Item head tail}
+                (.exec
+                  (..has! index head output)
+                  (again ("lux i64 +" 1 index) tail)))))))
+    <input>)])
+
+(def: underflow
+  Nat
+  (-- 0))
+
+(`` (template: (list|-default <empty> <array>)
+      [((.: (.All (_ a) (.-> (.List a) (..Array a) (.List a)))
+            (.function (list|-default empty array)
+              (.loop [index ("lux i64 -" 1 (..size array))
+                      output empty]
+                (.if ("lux i64 =" (~~ (.static ..underflow)) index)
+                  output
+                  (again ("lux i64 -" 1 index)
+                         (.if (..lacks? index array)
+                           output
+                           {.#Item (..item index array) output}))))))
+        <empty> <array>)]))
+
+(`` (template: (list|+default <default> <array>)
+      [((.: (.All (_ a) (.-> a (..Array a) (.List a)))
+            (.function (list|+default default array)
+              (.loop [index ("lux i64 -" 1 (..size array))
+                      output (`` (.: (.List (~~ (.as_is (~~ (.:of default)))))
+                                     {.#End}))]
+                (.if ("lux i64 =" (~~ (.static ..underflow)) index)
+                  output
+                  (again ("lux i64 -" 1 index)
+                         {.#Item (.if (..lacks? index array)
+                                   default
+                                   (..item index array))
+                                 output})))))
+        <default> <array>)]))
+
+(`` (template: .public (list <default> <array>)
+      [((.: (.All (_ a) (.-> (.Maybe a) (..Array a) (.List a)))
+            (.function (list default array)
+              (.case default
+                {.#Some default}
+                (~~ (..list|+default default array))
+
+                {.#None}
+                (~~ (..list|-default {.#End} array)))))
+        <default> <array>)]))
+
+(template: .public (= <//#=> <left/*> <right/*>)
+  [((.: (.All (_ a) (.-> (.-> a a .Bit) (..Array a) (..Array a) .Bit))
+        (.function (= //#= left/* right/*)
+          (.let [size (..size left/*)]
+            (.and ("lux i64 =" (..size right/*) size)
+                  (.loop [index 0]
+                    (.if ("lux i64 <" (.int size) (.int index))
+                      (.if (..lacks? index left/*)
+                        (..lacks? index right/*)
+                        (.if (..lacks? index right/*)
+                          .false
+                          (.and (//#= (..item index left/*)
+                                      (..item index right/*))
+                                (again ("lux i64 +" 1 index)))))
+                      true))))))
+    <//#=> <left/*> <right/*>)])
+
+(template: .public (composite <left/*> <right/*>)
+  [((.: (.All (_ a) (.-> (..Array a) (..Array a) (..Array a)))
+        (.function (composite left/* right/*)
+          (.let [|left| (..size left/*)
+                 |right| (..size right/*)]
+            (.|> (..empty ("lux i64 +" |left| |right|))
+                 (..copy! |left| 0 left/* 0)
+                 (..copy! |right| 0 right/* |left|)))))
+    <left/*> <right/*>)])
+
+(template: .public (mix <$> <init> <it>)
+  [((.: (.All (_ a b)
+          (.-> (.-> Nat b a a) a (..Array b) a))
+        (.function (mix $ init it)
+          (.let [size (..size it)]
+            (.loop [index 0
+                    so_far init]
+              (.if ("lux i64 <" (.int size) (.int index))
+                (.if (..lacks? index it)
+                  (again ("lux i64 +" 1 index) so_far)
+                  (again ("lux i64 +" 1 index) ($ index (..item index it) so_far)))
+                so_far)))))
+    <$> <init> <it>)])
+
+(template: .public (each <$> <input>)
+  [((.: (functor.Functor ..Array)
+        (.function (each $ input)
+          (..mix (.function (_ index item output)
+                   (..has! index ($ item) output))
+                 (..empty (..size input))
+                 input)))
+    <$> <input>)])
+
+(template [<name> <init> <op>]
+  [(template: .public (<name> <?> <it>)
+     [((.: (.All (_ a)
+             (.-> (.-> a .Bit)
+                  (.-> (..Array a) .Bit)))
+           (.function (<name> ? it)
+             (.let [size (..size it)]
+               (.loop [index 0]
+                 (.if ("lux i64 <" (.int size) (.int index))
+                   (.if (..lacks? index it)
+                     (again ("lux i64 +" 1 index))
+                     (<op> (? (..item index it))
+                           (again ("lux i64 +" 1 index))))
+                   <init>)))))
+       <?> <it>)])]
+
+  [every? .true  and]
+  [any?   .false or]
+  )
+
+(template: .public (one <?> <it>)
+  [((.: (.All (_ a b)
+          (.-> (.-> a (.Maybe b)) (..Array a) (.Maybe b)))
+        (.function (one ? it)
+          (.let [size (..size it)]
+            (.loop [index 0]
+              (.if ("lux i64 <" (.int size) (.int index))
+                (with_expansions [<again> (again ("lux i64 +" 1 index))]
+                  (.if (..lacks? index it)
+                    <again>
+                    (.case (? (..item index it))
+                      {.#None}
+                      <again>
+
+                      output
+                      output)))
+                {.#None})))))
+    <?> <it>)])