Fix two little errors

stdlib/array.mli

@@ -283,9 +283,9 @@ val stable_sort : ('a -> 'a -> int) -> 'a array -> unit
    elements that compare equal are kept in their original order) and
    not guaranteed to run in constant heap space.
 
-   The current implementation uses Merge Sort. It uses [n/2]
-   words of heap space, where [n] is the length of the array.
-   It is usually faster than the current implementation of {!sort}.
+   The current implementation uses Merge Sort. It uses a temporary array of
+   length [n/2], where [n] is the length of the array.  It is usually faster
+   than the current implementation of {!sort}.
 *)
 
 val fast_sort : ('a -> 'a -> int) -> 'a array -> unit

stdlib/arrayLabels.mli

@@ -283,9 +283,9 @@ val stable_sort : cmp:('a -> 'a -> int) -> 'a array -> unit
    elements that compare equal are kept in their original order) and
    not guaranteed to run in constant heap space.
 
-   The current implementation uses Merge Sort. It uses [n/2]
-   words of heap space, where [n] is the length of the array.
-   It is usually faster than the current implementation of {!sort}.
+   The current implementation uses Merge Sort. It uses a temporary array of
+   length [n/2], where [n] is the length of the array.  It is usually faster
+   than the current implementation of {!sort}.
 *)
 
 val fast_sort : cmp:('a -> 'a -> int) -> 'a array -> unit

stdlib/list.mli

@@ -388,7 +388,7 @@ val assoc : 'a -> ('a * 'b) list -> 'b
 val assoc_opt : 'a -> ('a * 'b) list -> 'b option
 (** [assoc_opt a l] returns the value associated with key [a] in the list of
     pairs [l]. That is,
-    [assoc a [ ...; (a,b); ...] = b]
+    [assoc a [ ...; (a,b); ...] = Some b]
     if [(a,b)] is the leftmost binding of [a] in list [l].
     Returns [None] if there is no value associated with [a] in the
     list [l].

stdlib/listLabels.mli

@@ -388,7 +388,7 @@ val assoc : 'a -> ('a * 'b) list -> 'b
 val assoc_opt : 'a -> ('a * 'b) list -> 'b option
 (** [assoc_opt a l] returns the value associated with key [a] in the list of
     pairs [l]. That is,
-    [assoc a [ ...; (a,b); ...] = b]
+    [assoc a [ ...; (a,b); ...] = Some b]
     if [(a,b)] is the leftmost binding of [a] in list [l].
     Returns [None] if there is no value associated with [a] in the
     list [l].