String.split

2 files changed, 26 insertions, 0 deletions

diff --git a/stdlib/string.ml b/stdlib/string.ml
index 7189ce99f3..3290283371 100644
--- a/stdlib/string.ml
+++ b/stdlib/string.ml
@@ -127,6 +127,17 @@ type t = string
 let compare (x: t) (y: t) = Pervasives.compare x y
 external equal : string -> string -> bool = "caml_string_equal"
 
+let split sep s =
+  let r = ref [] in
+  let j = ref (length s) in
+  for i = length s - 1 downto 0 do
+    if unsafe_get s i = sep then begin
+      r := sub s (i + 1) (!j - i - 1) :: !r;
+      j := i
+    end
+  done;
+  sub s 0 !j :: !r
+
 (* Deprecated functions implemented via other deprecated functions *)
 [@@@ocaml.warning "-3"]
 let uppercase s =
diff --git a/stdlib/string.mli b/stdlib/string.mli
index b7d895658f..11dd70205b 100644
--- a/stdlib/string.mli
+++ b/stdlib/string.mli
@@ -282,6 +282,21 @@ val equal: t -> t -> bool
 (** The equal function for strings.
     @since 4.03.0 *)
 
+val split: char -> string -> string list
+(** [String.split sep s] returns the list of all (possibly empty)
+    substrings of [s] that are delimited by the [sep] character.
+
+    The function's output is specified by the following invariants:
+
+    - The list is not empty.
+    - Concatenating its elements using [sep] as a separator returns a
+      string equal to the input ([String.concat (String.make 1 sep)
+      (String.split sep s) = s]).
+    - No string in the result contains the [sep] character.
+
+    @since 4.04.0
+*)
+
 (**/**)
 
 (* The following is for system use only. Do not call directly. *)