Newbie question: Unbound module Uchar.Utf8

Learning
1

I am completely new to Ocaml and I am trying to convert between utf8 and unicode code points. But unfortunately I am already stuck at calling the functions in the modules correctly. This is my code:

open Core
let () =
let c = Uchar.of_scalar 0x20ac in
match c with
| Some v → Printf.printf “item is %s\n” (Uchar.Utf8.to_string v)
| None → Printf.printf “Nothing”

The compiler complains about “Unbound module Uchar.Utf8”.
What am I doing wrong?
Thank you in advance for your help!
markusr

2

I am not a user of Core, but I suspect you have an old version of Core.

The latest versions (v0.17.0 and v0.17.1) have Core.Uchar.Utf8. Earlier versions do not.

You can see this by visiting https://ocaml.org/p/core/latest/doc/Core/Uchar/Utf8/index.html and navigating the versions in the top left corner.

Without more information about how you installed Core, you could try:

opam update
opam upgrade core
3

@jbeckford: You were right of course! My installation is just two days old, so I automatically checked the latest docs of Core and did not realise, that on my platform v0.17.x is not available yet. Thanks for your help and for the quick response.

4

Incidentally, note that you can do this using just the standard library:

# let utf8_of_scalar (n : int) : string =
    let buf = Buffer.create 0 in
    Buffer.add_utf_8_uchar buf (Uchar.of_int n);
    Buffer.contents buf
;;
val utf8_of_scalar : int -> string = <fun>
# utf8_of_scalar 0x20ac;;
- : string = "€"

Cheers,
Nicolas

2 Likes
5

You can even avoid using a Buffer:

# let uchar_to_utf_8 u =
    let b = Bytes.create (Uchar.utf_8_byte_length u) in
    ignore (Bytes.set_utf_8_uchar b 0 u);
    Bytes.unsafe_to_string b
  ;;
val uchar_to_utf_8 : Uchar.t -> string = <fun>
# uchar_to_utf_8 (Uchar.of_int 0x20AC);;
- : string = "€"
2 Likes
6

Thanks @nojb, @dbuenzli. It helps to know, that i could do this with the standard lib. Thx again.