add CCArray.of_iter

benchs/run_benchs.ml

@@ -1153,12 +1153,14 @@ module Iter_ = struct
   let bench_to_array n =
     let iter () = Iter.to_array Iter.(1 -- n)
     and gen () = Gen.to_array Gen.(1 -- n)
-    and oseq () = OSeq.to_array OSeq.(1 -- n) in
+    and oseq () = OSeq.to_array OSeq.(1 -- n)
+    and of_iter () = CCArray.of_iter Iter.(1 -- n) in
     B.throughputN 3 ~repeat
       [
         "iter.to_array", iter, ();
         "gen.to_array", gen, ();
         "oseq.to_array", oseq, ();
+        "ccarray.of_iter", of_iter, ();
       ]
 
   let bench_cons n =

src/core/CCArray.ml

@@ -466,6 +466,12 @@ let to_seq a =
 
 let to_iter a k = iter k a
 
+let of_iter (i : 'a iter) : 'a array =
+  let open CCVector in
+  let vec = create () in
+  i (push vec);
+  to_array vec
+
 let to_gen a =
   let k = ref 0 in
   fun () ->

src/core/CCArray.mli

@@ -240,6 +240,11 @@ val to_iter : 'a t -> 'a iter
     in modification of the iterator.
     @since 2.8 *)
 
+val of_iter : 'a iter -> 'a t
+(** [of_iter iter] builds a array from a given [iter].
+        In the result, elements appear in the same order as they did in the source [iter].
+     @since NEXT_RELEASE *)
+
 val to_seq : 'a t -> 'a Seq.t
 (** [to_seq a] returns a [Seq.t] of the elements of an array [a].
     The input array [a] is shared with the sequence and modification of it will result

src/core/CCArrayLabels.mli

@@ -248,6 +248,11 @@ val to_iter : 'a t -> 'a iter
     in modification of the iterator.
     @since 2.8 *)
 
+val of_iter : 'a iter -> 'a t
+(** [of_iter iter] builds a array from a given [iter].
+        In the result, elements appear in the same order as they did in the source [iter].
+     @since NEXT_RELEASE *)
+
 val to_seq : 'a t -> 'a Seq.t
 (** [to_seq a] returns a [Seq.t] of the elements of an array [a].
     The input array [a] is shared with the sequence and modification of it will result

tests/core/t_array.ml

@@ -309,3 +309,6 @@ q ~count:300 arr_arbitrary (fun a ->
     Array.sort CCInt.compare a1;
     sort_generic (module IA) ~cmp:CCInt.compare a2;
     a1 = a2)
+;;
+
+q Q.(array int) (fun a -> of_iter (to_iter a) = a)