ocaml: phase 6 Option/Result/Bytes extensions (+9 tests, 439 total)

Option: join, to_result, some, none.
Result: value, iter, fold.
Bytes: length, get, of_string, to_string, concat, sub — thin alias of
String (SX has no separate immutable byte type).

Ordering fix: Bytes module placed after String so its closures capture
String in scope. Earlier draft put Bytes before String which made
String.* lookups fail with 'not a record/module' (treated as nullary
ctor).

lib/ocaml/runtime.sx

@@ -274,6 +274,19 @@
        match o with
        | None -> []
        | Some x -> [x]
+
+     let join oo =
+       match oo with
+       | None -> None
+       | Some inner -> inner
+
+     let to_result none_v o =
+       match o with
+       | None -> Error none_v
+       | Some x -> Ok x
+
+     let some x = Some x
+     let none = None
    end ;;
 
    module Result = struct
@@ -316,6 +329,21 @@
        match r with
        | Ok x -> Some x
        | Error _ -> None
+
+     let value r default =
+       match r with
+       | Ok x -> x
+       | Error _ -> default
+
+     let iter f r =
+       match r with
+       | Ok x -> f x
+       | Error _ -> ()
+
+     let fold ok_f err_f r =
+       match r with
+       | Ok x -> ok_f x
+       | Error e -> err_f e
    end ;;
 
    module String = struct
@@ -334,6 +362,16 @@
      let index_of s sub = _string_index_of s sub
    end ;;
 
+   module Bytes = struct
+     (* Thin alias of String — SX has no separate immutable byte type. *)
+     let length s = String.length s
+     let get s i = String.get s i
+     let of_string s = s
+     let to_string s = s
+     let concat sep xs = String.concat sep xs
+     let sub s i n = String.sub s i n
+   end ;;
+
    module Char = struct
      let code c = _char_code c
      let chr n = _char_chr n