Merge pull request #2825 from mikaelbr/array-partition

Add Belt_Array.partition

Author: bobzhang

Diff for: jscomp/others/belt_Array.ml

@@ -408,13 +408,36 @@ let cmpU a b p =
 
 let cmp a b p = cmpU a b (fun[@bs] a b -> p a b)
 
+let partitionU a f =
+  let l = length a in
+  let i = ref 0 in
+  let j = ref 0 in
+  let a1 = makeUninitializedUnsafe l in
+  let a2 = makeUninitializedUnsafe l in
+  for ii = 0 to l - 1 do
+    let v = getUnsafe a ii in
+    if f v [@bs] then (
+      setUnsafe a1 !i v;
+      incr i
+    )
+    else (
+      setUnsafe a2 !j v;
+      incr j
+    )
+  done;
+  truncateToLengthUnsafe a1 !i;
+  truncateToLengthUnsafe a2 !j;
+  (a1, a2)
+
+let partition a f = partitionU a (fun [@bs] x -> f x)
+
 let unzip a =
   let l = length a in
-  let a1 = makeUninitializedUnsafe l in 
-  let a2 = makeUninitializedUnsafe l in 
+  let a1 = makeUninitializedUnsafe l in
+  let a2 = makeUninitializedUnsafe l in
   for i = 0 to l - 1 do
     let (v1, v2) = getUnsafe a i in
     setUnsafe a1 i v1;
-    setUnsafe a2 i v2    
+    setUnsafe a2 i v2
   done;
   (a1, a2)

Diff for: jscomp/others/belt_Array.mli

@@ -411,7 +411,18 @@ val mapWithIndex: 'a array ->  (int -> 'a -> 'b ) -> 'b array
       [|0 + 1; 1 + 2; 2 + 3|]
     ]}
 *)
-    
+
+
+val partitionU : 'a array -> ('a -> bool [@bs]) -> 'a array * 'a array
+val partition : 'a array ->  ('a -> bool) -> 'a array * 'a array
+(** [partition f a] split array into tuple of two arrays based on predicate f; first of tuple where predicate vause true, second where predicate cause false
+
+    @example {[
+      predicate [|1;2;3;4;5|] (fun x -> if x mod 2 = 0)  = ([|2;4|], [|1;2;3|]);;
+      predicate [|1;2;3;4;5|] (fun x -> if x mod 2 <> 0) = ([|1;2;3|], [|2;4|]);;
+    ]}
+*)
+
 val reduceU:  'b array -> 'a -> ('a -> 'b -> 'a [@bs]) ->'a
 val reduce:  'b array -> 'a -> ('a -> 'b -> 'a ) ->'a
 (** [reduce xs init f]