Problem compiling program that uses Uchar.of_int

Learning
1

Hi, I created this simple function in utop:

let get_random_hanzi () =
  let buf = Buffer.create 1 in
  let chr = Random.int_incl 0x4e00 0x9fff |> Uchar.of_int in
  Buffer.add_utf_8_uchar buf chr;
  Buffer.contents buf

It works fine, so I saved it inside a file and then created this jbuild file to compile it:

(jbuild_version 1)

(executable
 ((name hello)
  (libraries (core))))

When I run jbuilder build hello.exe, I get this error:

Error: Unbound value Uchar.of_int

I don’t quite understand why it works fine in utop but doesn’t work at all when I try to compile…

2

The core library redefines the Uchar module. In particular, its version of Uchar.of_int is Uchar.of_scalar_exn.

1 Like
3

Thanks so much! That worked, but I had to make one more change before my program would compile. I had to change Buffer.add_utf_8_uchar buf chr to Caml.Buffer.add_utf_8_uchar buf chr. The full program looks like this:

open Base
open Stdio

let get_random_hanzi () =
  let buf = Buffer.create 1 in
  let chr = Random.int_incl 0x4e00 0x9fff |> Uchar.of_scalar_exn in
  Caml.Buffer.add_utf_8_uchar buf chr;
  Buffer.contents buf

let () =
  print_endline "你好世界！";
  Random.self_init();
  print_endline ("Random hanzi: " ^ get_random_hanzi())

Is there a better way to write that, or does it look more or less OK?

4

This seems quite good to me: It seems that the base library version was not updated with the new unicode specific function in Buffer. In this case, using Caml.Buffer is the right thing to do.

Alternatively, you could use the Format or Printf module for the printing:

let ( ) = Random.self_init ()
let ( ) = Format.printf "你好世界!@.Random hanzi:%s@." (get_random_hanzi ())
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