1 files changed, 65 insertions, 32 deletions
diff --git a/stdlib/source/library/lux/data/collection/sequence.lux b/stdlib/source/library/lux/data/collection/sequence.lux
index 4a2beb94f..07ebeba76 100644
--- a/stdlib/source/library/lux/data/collection/sequence.lux
+++ b/stdlib/source/library/lux/data/collection/sequence.lux
@@ -2,35 +2,35 @@
 ... https://hypirion.com/musings/understanding-persistent-vector-pt-2
 ... https://hypirion.com/musings/understanding-persistent-vector-pt-3
 (.using
-  [library
-   [lux {"-" list}
-    ["@" target]
-    [abstract
-     [functor {"+" Functor}]
-     [apply {"+" Apply}]
-     [monad {"+" Monad do}]
-     [equivalence {"+" Equivalence}]
-     [monoid {"+" Monoid}]
-     [mix {"+" Mix}]
-     [predicate {"+" Predicate}]]
-    [control
-     ["[0]" maybe]
-     ["[0]" try {"+" Try}]
-     ["[0]" exception {"+" exception:}]
-     ["<>" parser
-      ["<[0]>" code {"+" Parser}]]]
-    [data
-     ["[0]" product]
-     [collection
-      ["[0]" list ("[1]#[0]" mix functor monoid)]
-      ["[0]" array {"+" Array} ("[1]#[0]" functor mix)]]]
-    [macro
-     [syntax {"+" syntax:}]
-     ["[0]" code]]
-    [math
-     [number
-      ["n" nat]
-      ["[0]" i64]]]]])
+ [library
+  [lux {"-" list}
+   ["@" target]
+   [abstract
+    [functor {"+" Functor}]
+    [apply {"+" Apply}]
+    [monad {"+" Monad do}]
+    [equivalence {"+" Equivalence}]
+    [monoid {"+" Monoid}]
+    [mix {"+" Mix}]
+    [predicate {"+" Predicate}]]
+   [control
+    ["[0]" maybe]
+    ["[0]" try {"+" Try}]
+    ["[0]" exception {"+" exception:}]
+    ["<>" parser
+     ["<[0]>" code {"+" Parser}]]]
+   [data
+    ["[0]" product]
+    [collection
+     ["[0]" list ("[1]#[0]" mix functor monoid)]
+     ["[0]" array {"+" Array} ("[1]#[0]" functor mix)]]]
+   [macro
+    [syntax {"+" syntax:}]
+    ["[0]" code]]
+   [math
+    [number
+     ["n" nat]
+     ["[0]" i64]]]]])
 
 (type: (Node a)
   (Variant
@@ -300,11 +300,11 @@
                                 sequence))}
       (exception.except ..index_out_of_bounds [sequence idx]))))
 
-(def: .public (revised idx f sequence)
+(def: .public (revised idx revision it)
   (All (_ a) (-> Nat (-> a a) (Sequence a) (Try (Sequence a))))
   (do try.monad
-    [val (..item idx sequence)]
-    (..has idx (f val) sequence)))
+    [val (..item idx it)]
+    (..has idx (revision val) it)))
 
 (def: .public (prefix sequence)
   (All (_ a) (-> (Sequence a) (Sequence a)))
@@ -498,3 +498,36 @@
   [every? array.every? #1 and]
   [any?   array.any?   #0 or]
   )
+
+(def: .public (only when items)
+  (All (_ a) (-> (-> a Bit) (Sequence a) (Sequence a)))
+  (..mix (function (_ item output)
+           (if (when item)
+             (..suffix item output)
+             output))
+         ..empty
+         items))
+
+(def: (one|node check items)
+  (All (_ a b)
+    (-> (-> a (Maybe b)) (Node a) (Maybe b)))
+  (case items
+    {#Base items}
+    (array.one check items)
+    
+    {#Hierarchy items}
+    (array.one (one|node check) items)))
+
+(def: .public (one check items)
+  (All (_ a b)
+    (-> (-> a (Maybe b)) (Sequence a) (Maybe b)))
+  (case (|> items
+            (value@ #root)
+            (array.one (one|node check)))
+    {.#None}
+    (|> items
+        (value@ #tail)
+        (array.one check))
+    
+    output
+    output))