From 69c4f089bda2d88f38248b818eea9686b137e787 Mon Sep 17 00:00:00 2001
From: Josh Berdine <jjb@fb.com>
Date: Mon, 28 Jun 2021 03:34:10 -0700
Subject: [PATCH] [sledge] Add Array.of_list_map

Reviewed By: ngorogiannis

Differential Revision: D28907815

fbshipit-source-id: 40ed1f29e
---
 sledge/nonstdlib/array.ml  | 13 +++++++++++++
 sledge/nonstdlib/array.mli |  1 +
 2 files changed, 14 insertions(+)

diff --git a/sledge/nonstdlib/array.ml b/sledge/nonstdlib/array.ml
index 282e6b861..7e45a2eca 100644
--- a/sledge/nonstdlib/array.ml
+++ b/sledge/nonstdlib/array.ml
@@ -27,6 +27,19 @@ let of_list_rev = function
       in
       back_fill (len - 2) tl
 
+let of_list_map xs ~f =
+  match xs with
+  | [] -> [||]
+  | hd :: tl ->
+      let a = make (1 + List.length tl) (f hd) in
+      let rec fill i = function
+        | [] -> a
+        | hd :: tl ->
+            unsafe_set a i (f hd) ;
+            fill (i + 1) tl
+      in
+      fill 1 tl
+
 let is_empty = function [||] -> true | _ -> false
 let map xs ~f = map ~f xs
 let mapi xs ~f = mapi ~f xs
diff --git a/sledge/nonstdlib/array.mli b/sledge/nonstdlib/array.mli
index 06fc28d8c..a4e113f9f 100644
--- a/sledge/nonstdlib/array.mli
+++ b/sledge/nonstdlib/array.mli
@@ -13,6 +13,7 @@ type 'a t = 'a array [@@deriving compare, equal, sexp]
 val of_ : 'a -> 'a t
 val of_iter : 'a iter -> 'a t
 val of_list_rev : 'a list -> 'a t
+val of_list_map : 'a list -> f:('a -> 'b) -> 'b t
 val map : 'a t -> f:('a -> 'b) -> 'b t
 val mapi : 'a t -> f:(int -> 'a -> 'b) -> 'b t