zdancewic / owl

Universal toplevel for OCaml

owl - an interactive toploop for OCaml education

Owl is a modified version of the utop package, with simplified features and default libraries that are geared toward novice programmers.

The main differences from utop are:

• owl provides simpler default settings and exposes fewer libraries
• owl wraps some of the OCaml libraries to make them more accessible
• owl comes bundled with some modules designed for learning about programming

Installation via opam

TODO!

Usage

To use owl, simply run:

$ owl

owl display a bar after the prompt which is used to show possible completions in real-time. You can navigate in it using M-left and M-right, and select one completion using M-tab. The M denotes the meta key, which is Alt most of the time.

Creating a custom utop-enabled toplevel

With jbuilder

The recommended way to build a custom utop toplevel is via jbuilder. The entry point of the custom utop must call UTop_main.main. For instance write the following myutop.ml file:

let () = UTop_main.main ()

and the following jbuild file:

(executable
 ((name myutop)
  (link_flags (-linkall))
  (libraries (utop))))

then to build the toplevel, run:

$ jbuilder myutop.bc

Note the -linkall in the link flags. By default OCaml doesn't link unused modules, however for a toplevel you don't know in advance what the user is going to use so you must link everything.

If you want to include more libraries in your custom utop, simply add them to the (libraries ...) field.

Additionally, if you want to install this topevel, add the two following fields to the executable stanza:

  (public_name myutop)
  (modes (byte))

The (modes ...) field is to tell jbuilder to install the byte-code version of the executable, as currently native toplevels are not fully suported.

Utop

Please see the [utop documentation]:https://github.com/diml/utop for more configuration options.

Owl would not be possible without utop. Many thanks to Jeremie Dimino [email protected] who developed the original utop code base.