pcattori / ocaml-cheatsheet

ocaml cheatsheet

Notes from when I went on Dillon Mulroy's Twitch stream to talk about getting started with OCaml.

learning

The official "Learn OCaml" docs are always improving, but here are some other resources I found invaluable when starting out.

Tools & techniques

👉 Real World OCaml

• Command-line parsing
• Error handling
• Maps and hash tables
• Serialization
• JSON
• Testing

Programming language design & theory

👉 OCaml Programming: Correct + Efficient + Beautiful

• Implementing an interpreter in OCaml
• The Curry-Howard Correspondence

project setup

dune init proj <name>
cd <name>
opam switch create . --deps-only

Minimal dune-project for CLIs:

(lang dune 3.11)

(generate_opam_files true)

(package
 (name <name of your cli>)
 (depends ocaml dune))

git

Initialize a git repo:

git init

Then add a .gitignore:

_build/
_opam/

opam switch

Setup opam to auto-enable the switch when entering the directory:

opam init --enable-shell-hook

Or do this every time:

eval $(opam env)

dev dependencies

opam install ocaml-lsp-server odoc ocamlformat utop

neovim

Do not do the rtp thing that opam suggests. Instead, do this if using lazy.nvim as your package manager:

-- ~/.config/nvim/lua/plugins/ocaml.lua

return {
  {
    "neovim/nvim-lspconfig",
    opts = {
      servers = {
        -- use local lsp installed within project's opam switch
        ocamllsp = { mason = false },
      },
    },
  },
  {
    "nvim-treesitter/nvim-treesitter",
    opts = function(_, opts)
      if type(opts.ensure_installed) == "table" then
        vim.list_extend(opts.ensure_installed, { "ocaml", "ocaml_interface" })
      end
    end,
  },
}