Add Array.getBy

Author: bloodyowl

jscomp/others/belt_Array.ml

@@ -265,6 +265,22 @@ let mapU a f =
 
 let map a f = mapU a (fun[@bs] a -> f a)
 
+let getByU a p =
+  let l = length a in
+  let i = ref 0 in
+  let r = ref None in
+  while !r == None && !i < l do
+    let v = (getUnsafe a !i) in
+    if p v [@bs] then
+      begin
+        r := Some v;
+      end;
+    incr i
+  done;
+  !r
+
+let getBy a p = getByU a (fun[@bs] a -> p a)
+
 let keepU a f =
   let l = length a in
   let r = makeUninitializedUnsafe l in

jscomp/others/belt_Array.mli

@@ -369,6 +369,16 @@ val map: 'a array ->  ('a -> 'b ) -> 'b array
 
 *)
 
+val getByU: 'a t -> ('a -> bool [@bs]) -> 'a option
+val getBy: 'a t -> ('a -> bool) -> 'a option
+(** [getBy xs p] returns [Some value] for the first value in [xs] that satisifies the predicate function [p]; returns [None] if no element satisifies the function.
+
+  @example {[
+      getBy [|1;4;3;2|] (fun x -> x mod 2 = 0) = Some 4
+      getBy [|15;13;11|] (fun x -> x mod 2 = 0) = None
+    ]}
+*)
+
 val keepU: 'a array -> ('a -> bool [@bs]) -> 'a array
 val keep: 'a array -> ('a -> bool ) -> 'a array
 (** [keep xs p ]