feat(BV): add init

Author: c-cube

src/data/CCBV.ml

@@ -67,7 +67,7 @@ let bytes_length_of_size size =
   else
     div_ size + 1
 
-let create ~size default =
+let create ~size default : t =
   if size = 0 then
     empty ()
   else (
@@ -210,6 +210,13 @@ let[@inline] set bv i =
       (unsafe_get_ bv.b idx_bucket lor (1 lsl idx_in_byte))
   )
 
+let init size f : t =
+  let v = create ~size false in
+  for i = 0 to size - 1 do
+    if f i then set v i
+  done;
+  v
+
 let[@inline] reset bv i =
   if i < 0 then
     invalid_arg "reset: negative index"

src/data/CCBV.mli

@@ -23,6 +23,11 @@ val create : size:int -> bool -> t
 (** Create a bitvector of given size, with given default value.
     Length of result is [size]. *)
 
+val init : int -> (int -> bool) -> t
+(** [init len f] initializes a bitvector of length [len], where bit [i]
+    is true iff [f i] is.
+    @since NEXT_RELEASE *)
+
 val copy : t -> t
 (** Copy of bitvector. *)