Ocaml IO - Printing Contents of a buffer

Learning
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1

I am still learning ocaml and have run into an issue printing the contents of a buffer to stdout (or anything to be honest). I have tried using the buffered channels and string conversions but nothing seems to work. Even calling this (Stdio.Out_channel.output_string Stdio.stdout "lookey here";) does not print to stdout so I am not sure how to verify that my buffer ever gets updated. However, I have noticed white spaces show up instead of my desired output.

open Base

let interpret tokens =
  let tape = Array.create ~len:30000 0 in
  let outt = Buffer.create 500 in
  let rec execute acc tokens ptr =
    match tokens with
    ...
    | Dot :: rest ->
      Buffer.add_char outt (Char.unsafe_of_int tape.(ptr));
      Stdio.Out_channel.output_string Stdio.stdout "lookey here";
      execute (Dot :: acc) rest ptr
    | Comma :: rest -> 
      let ch = Stdio.In_channel.input_char Stdio.stdin in
        tape.(ptr) <-  Option.value_map ch ~default:0 ~f:Char.to_int;
      execute (Comma :: acc) rest ptr
  in
    Stdio.Out_channel.output_buffer Stdio.stdout outt;
    Stdio.Out_channel.flush Stdio.stdout;
    execute [] tokens 0

This sample uses the Base module but my prior attempts didn’t and still would not return the desired result.

2

Channels in OCaml are buffered. Have you tried calling flush stdout after calling output_string ?

Cheers,
Nicolas

3

I have. same effect. Sorry my sample didnt reflect that

4

What happens when you try running this program?

let () =
  let buf = Buffer.create 80 in
  Buffer.add_string buf "Hello, World\n";
  Stdio.Out_channel.output_buffer Stdio.stdout buf;
  Stdio.Out_channel.flush Stdio.stdout
5

Or, using only the OCaml standard library and none of this Base stuff,

let () =
  let buf = Buffer.create 80 in
  Buffer.add_string buf "Hello, World\n";
  Buffer.output_buffer Stdlib.stdout buf;
  Stdlib.flush Stdlib.stdout
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