Tooling is Awesome

ven. 16 octobre 2015 by simon

A quick note about my current OCaml setup, in my last project, Nunchaku.


First, I use Oasis to manage and build the project. It relies on OCamlbuild, but brings in several niceties:

  • automatic generation of configure and Makefile files.
  • it deals with sub-libraries, and the configure script can enable or disable the build of each sub-library.
  • it builds and runs my tests. Yay!


Oh dear. Merlin has improved my workflow with OCaml so much that I can't imagine working without it now. I can use it with Vim, but it also works for emacs users, so everyone is happy. The basics features I use are the ability to ask for the type of any expression (cursor on it, then \t), and the omni-completion of functions and modules in the same project or from (ocamlfind) libraries.

Incidentally, my vim setup includes a file ~/.vim/after/ftplugin/ocaml.vim containing

au filetype ocaml   :setlocal comments=sr:(*,m1:\ ,e:*)
au filetype ocaml   :nmap <leader>d :MerlinDestruct<CR>
au filetype ocaml   :nmap <leader>r :MerlinRename

au filetype ocaml   :syn sync maxlines=1500

The two middle lines are key bindings:

  • map \d to :MerlinDestruct, which decomposes variables into constructors in pattern matches.
  • map \r to :MerlinRename, to easily change the name of functions or variables (yes, it's better than a regex, because it knows about scoping).

Auto rebuild

The Makefile contains a target make watch that will loop forever, watching for changes in .ml files to recompile. It looks like this (careful, use tabs, as always with Makefiles):


    while find src/ -print0 | \
     xargs -0 inotifywait -e delete_self -e modify ;\
    do \
      echo "============ at `date` ==========" ; \
      make ; \


Well, that's it. I also use some other things, including of course Opam and opam.vim.

I will post something about the internals of Nunchaku some day, it has a cool 5-arguments GADT ;-)