OCaml: Package management

opam

opam switches are comparable to python's venvs: https://ocaml.org/docs/opam-switch-introduction

• Show switches available to be installed: opam switch list-available

  • Show pre-releases as well: opam switch list-available --all

• Activate: eval $(opam env)

• Create new switch: opam switch create <switch-name>

  • Make a new switch with a specific compiler version (v5.1.1): opam switch create 5.1.1

• Delete a switch: opam switch remove <switch-name>

  • Default switch is named default ??

• List switches: opam switch

• Go to a switch: opam switch <switch-name>

• List installed packages: opam list or opam list -i

  • List all available packages: opam list -a

• Change switch: opam switch set <switch-name>

• Install a package (to current switch): opam install <package-name>

• Remove a package: opam remove <package-name>

• Update package list: opam update

• Show version of an installed package: opam info <package-name>

—

Many useful packages related to Coq are available only after adding this repo:

opam repo add coq-released https://coq.inria.fr/opam/released

Reference: https://opam.ocaml.org/doc/Usage.html

dune

General

• ocamllex has its own stanza:
  • https://dune.readthedocs.io/en/latest/reference/dune/ocamllex.html
  • https://stackoverflow.com/questions/77159120/how-can-i-add-the-ml-flag-or-any-flag-really-to-ocamllex-in-a-dune-file
• Run an executable:
  • dune exec ./lexer.exe
  • dune adds a .exe extension to the executables that it makes
• name field of executable is the entry point.
  • Could be main for main.ml

Starting off

# Initialize new project
dune init proj <proj-name>

dune build
dune exec

References: https://ocaml.org/docs/up-and-running

Both of the following are equivalent??

dune exec -- <cmd>
dune install; <cmd>

Don't treat a warning as error

(executable
  (name lexer)
  (flags (:standard (-warn-error -32))))

https://dune.readthedocs.io/en/latest/concepts/ocaml-flags.html

Useful packages/tools

• ocamlc: bytecode compiler
• ocamlopt: native code compiler
• merlin: ocaml code completion for text editors
• utop: like an enhanced ocaml REPL
• ocamlfind: ??
• js_ofocaml: make web stuff from ocaml
  • effectively allows running ocaml equivalent code as javascript

Jane Street libraries:

• base: a ocaml stdlib (minimal, lightweight, stable API, no dependencies)
• core: much more than base
• core_kernel: more than base, less than core
• hardcaml: hardware designs with ocaml

Historical:

• oasis: an old build tool that was used before dune came along
• jbuilder: earlier name of dune

Loading base (Jane Street)

base is a package from janestreet.

# #use "topfind";;
# #require "base";;
# open Base;;

base < core_kernel < core

The extra # are needed.