js_top_worker Feature Demo

Basic Execution exec

let greet name = Printf.sprintf "Hello, %s!" name;;
greet "OCaml";;

Multiple Environments isolation

let env_value = 42;;

MIME Output rich output

(* SVG output *)
let svg = {|<svg width="100" height="100">
  <circle cx="50" cy="50" r="40" fill="#89b4fa"/>
  <text x="50" y="55" text-anchor="middle" fill="white">OCaml</text>
</svg>|};;
Mime_printer.push "image/svg" svg;;

Autocomplete complete_prefix

List.ma

Enter partial code and click Complete to see suggestions

Type Information type_enclosing

let f x = List.map (fun y -> y + 1) x

Position (0-indexed):

Click "Get Type" to see type information

Error Reporting query_errors

let x : string = 42
let unused = "hello"
let y = unknown_function ()

Click "Check Errors" to analyze code

Directives #show, #install_printer, etc.

#show List.map;;

Custom Printers #install_printer

type color = Red | Green | Blue;;

let pp_color fmt c =
  Format.fprintf fmt "[COLOR:%s]"
    (match c with Red -> "red" | Green -> "green" | Blue -> "blue");;

#install_printer pp_color;;

[Red; Green; Blue];;

Library Loading #require

Libraries must be prepared with jtw opam first.

#require "str";;
Str.split (Str.regexp ",") "a,b,c";;

Toplevel Script Execution exec_toplevel

Toplevel scripts use "# " prefix for input lines. Output is indented.

# let square x = x * x;;
# let numbers = [1; 2; 3; 4; 5];;
# List.map square numbers;;