Company-coq

A collection of extensions for Proof General's Coq mode.

See screenshots below, or jump right to setup instructions and try the tutorial with M-x company-coq-tutorial after setting up!

Setup

MELPA

Both proof-general and company-coq are on MELPA, a repository of Emacs packages. Skip this step if you already use MELPA. Otherwise, add the following to your .emacs and restart Emacs:

(require 'package)
(add-to-list 'package-archives '("melpa" . "https://melpa.org/packages/") t)
(package-initialize)

Proof General and Company-Coq

Install and byte-compile Proof General, Company-Coq, and its dependencies by typing successively:

• M-x package-refresh-contents RET
• M-x package-install RET proof-general RET
• M-x package-install RET company-coq RET

(some dependencies will produce a few warnings; that's OK).

To enable company-coq automatically, add the following to your .emacs:

;; Load company-coq when opening Coq files
(add-hook 'coq-mode-hook #'company-coq-mode)

Then restart and launch the tutorial with M-x company-coq-tutorial!

Screenshots

Prettification of operators, types, and subscripts

Auto-completion

Snippets and smart commands

Outlines, code folding, and jumping to definition

Help with errors

Misc. extensions of Proof General

Citing

Use M-x company-coq-cite to insert the BibTeX entries for Coq, Proof General, and company-coq in the current buffer.

@InProceedings{CompanyCoq2016,
  Title     = {Company-Coq: Taking Proof General one step closer to a real IDE},
  Author    = {Pit-Claudel, Clément and Courtieu, Pierre},
  Booktitle = {CoqPL'16: The Second International Workshop on Coq for PL},
  Year      = {2016},
  Month     = jan,
  Doi       = {10.5281/zenodo.44331},
  Url       = {http://hdl.handle.net/1721.1/101149}
}

Quick start guide

You can check out the interactive tutorial by pressing M-x company-coq-tutorial RET. See also the screenshots above!

company-coq should be pretty transparent. Completion windows will pop up when company-coq has suggestions to make. By default, this would be when you start writing a tactic name or a command. You can also launch manual completion by using C-RET (or whatever was originally assigned to proof-script-complete in Coq mode).

Once auto-completion has started, the following key bindings are available:

• RET selects a completion
• C-g interrupts completion.
• C-h and <f1> display documentation for the currently highlighted keyword, identifier, or tactic.
• C-M-v scrolls down in the documentation window.
• C-w opens source view when available (alternatively, pressing M-. browses to the definition of the identifier at point).

Selecting a completion often inserts a snippet with holes at the current point (company-coq uses yasnippet as the snippet backend). You can move between holes by using <tab> and S-<tab>.

Loading company-coq also binds the following keys:

• M-RET inserts a new match case (| _ => _).
• M-S-RET inserts a new match goal rule (| [ H: _ |- _ ] => _).
• C-c C-a C-x extracts the current goal into a separate lemma.
• C-down-mouse-1 (i.e. C-click) shows an inline quick help box for the identifier under point. The box disappears when the mouse is released. Pressing the <menu> key or M-F12 also works.
• M-. jumps to the source of the identifier at point, when available.
• C-c C-d opens the documentation of the identifier at point (for theorems and definitions; for tactics, use C-h during completion).
• C-c C-, opens an outline of the code in a separate buffer (using occur).
• C-c C-/ folds the current definition, or all definitions in the file if repeated.
• C-c C-\ unfolds the current definition, or all definitions in the file if repeated.
• S-TAB folds or unfolds the current bullet or curly-brace-delimited block. With C-u, S-TAB folds all bullets and braces in the current buffer.
• C-c C-& looks up (grep) the current word in files in the current directory's subtree.
• C-c C-a C-e tries to match the last output to a documented error message, and displays the relevant section of the manual if it finds one.
• C-c C-a C-d parses the last unification error, and shows a diff of the two types that can't unify. If there is no such error, C-c C-a C-d shows a diff comparing the last goal to the previous one.

Tips

• Most completion engines support fuzzy matching: you can type Require Import C.N..Ab.ZPa and press RET to insert Coq.Numbers.Integer.Abstract.ZParity, and typing setrewin is enough to insert setoid_rewrite term in ident. You can (and must) omit spaces: SLD will insert Set Ltac Debug (of course SetLtDeb will also work), and ULD will insert Unset Ltac Debug.
• Using M-S-RET to insert new cases in a match goal saves a lot of time (and finger contortions). For the match itself, use mgw (for match goal with).
• The point-and-click feature (quick help) also works in non-graphic mode, if you enable xterm-mouse-mode.
• company-coq improves on some of Proof General's features. Try C-c C-a RET nat RET.
• Try right-clicking on a [Require Import] statement.
• Use a__b to display ab.

company-coq is implemented as a collection of small modules implementing independent features; check out M-x customize-variable RET company-coq-disabled-features RET and M-x customize-group RET company-coq RET for more info!

Troubleshooting

Empty squares in place of math operators, or incorrect line spacing

If you see blank squares appear where there should be math symbols (forall, exists, etc.), or if some lines suddenly become very tall, you may be missing a proper math font. See Installing a math font, or insert the following snippet in your .emacs to disable symbols beautification:

;; Disable symbol prettification
(setq company-coq-disabled-features '(prettify-symbols))

On the other hand, if you like the prettification feature a lot, you can enable it in the terminal:

(setq company-coq-features/prettify-symbols-in-terminals t)

Technical note: Proof General also offers a Unicode keywords facility. company-coq's implementation is based on the prettify-symbols-mode facility found in Emacs 24.4+, yielding a more compact (and faster?) implementation.

Advanced topics

Installing a math font

For prettification to work properly, you'll need a font with proper symbol support. Symbola (up to version 10.23), FreeMono, XITS Math, Segoe UI Symbol, Latin Modern, and Cambria Math will all work. If Emacs doesn't fallback properly, you can use the following snippet (change XITS Math and DejaVu sans Mono to the Unicode font you just downloaded and to your usual monospace font, respectively):

(set-fontset-font t 'unicode (font-spec :name "XITS Math") nil 'prepend)
(set-fontset-font t 'greek (font-spec :name "DejaVu sans Mono") nil 'prepend)

Or, in Emacs < 25:

(dolist (ft (fontset-list))
  (set-fontset-font ft 'unicode (font-spec :name "YOUR-USUAL-FONT"))
  (set-fontset-font ft 'unicode (font-spec :name "XITS Math") nil 'append))

Fixing math indentation

Using a variable-width font for symbols will break indentation. See this other project of mine to download a monospace-friendly symbols font. You'll want to replace the snippet above by following (adjusting Latin Modern Math and DejaVu sans Mono as appropriate):

(set-fontset-font t 'unicode (font-spec :name "Latin Modern Math Monospacified for DejaVu sans Mono") nil 'prepend)

Or, in Emacs < 25:

(dolist (ft (fontset-list))
  (set-fontset-font ft 'unicode (font-spec :name "YOUR-USUAL-FONT"))
  (set-fontset-font ft 'unicode (font-spec :name "Latin Modern Math Monospacified for YOUR-USUAL-FONT") nil 'append))

Folding all goals when a file is opened

Adding the following header to a Coq file will make company-coq hide the bodies of all bullets when the file is opened. You can also customize the company-coq-initial-state variable to apply the setting globally.

(* -*- company-coq-initial-fold-state: bullets; -*- *)

Showing alerts for long-running proofs

If possible, company-coq will use the alert library to display notifications when long-running proofs complete. alert is only needed on Windows and OSX; on Linux systems with DBus this should work out of the box. You can try it out by running the snippet below and opening another application while the proof runs; after 10 seconds company-coq will show a notification.

Goal True.
  Fail timeout 10 repeat pose 1.

Registering your own symbols and math operators

For a single file

Add the following header to a Coq file, save, and run M-x revert-buffer to prettify squiggly arrows.

(* -*- company-coq-local-symbols: (("<~>" . ?↭) ("~>" . ?↝) ("<~" . ?↜)); -*- *)

Alternatively, you can use a special comment at the end of the file:

(* Local Variables: *)
(* company-coq-local-symbols: (("<~>" . ?↭) ("~>" . ?↝) ("<~" . ?↜)) *)
(* End: *)

Tip: you can use M-x add-file-local-variable to add this sort of variables.

For a single project

Create a .dir-locals.el file at the root of your project, and add following contents to it:

;;; Directory Local Variables
;;; For more information see (info "(emacs) Directory Variables")

((coq-mode
  (company-coq-dir-local-symbols
   (("<~>" . ?↭) ("~>" . ?↝) ("<~" . ?↜)))))

Tip: you can use M-x add-dir-local-variable to add this sort of variables.

For all Coq files

Adjust and use the following snippet to register your own prettifications for all Coq files. This must run before (company-coq-mode), so it must be added after the company-coq setup code above.

(add-hook 'coq-mode-hook
          (lambda ()
            (setq-local prettify-symbols-alist
                        '((":=" . ?≜) ("Proof." . ?∵) ("Qed." . ?■)
                          ("Defined." . ?□) ("Time" . ?⏱) ("Admitted." . ?😱)))))

Greek symbols can be obtained using the following mappings:

'(("Alpha" . ?Α) ("Beta" . ?Β) ("Gamma" . ?Γ)
  ("Delta" . ?Δ) ("Epsilon" . ?Ε) ("Zeta" . ?Ζ)
  ("Eta" . ?Η) ("Theta" . ?Θ) ("Iota" . ?Ι)
  ("Kappa" . ?Κ) ("Lambda" . ?Λ) ("Mu" . ?Μ)
  ("Nu" . ?Ν) ("Xi" . ?Ξ) ("Omicron" . ?Ο)
  ("Pi" . ?Π) ("Rho" . ?Ρ) ("Sigma" . ?Σ)
  ("Tau" . ?Τ) ("Upsilon" . ?Υ) ("Phi" . ?Φ)
  ("Chi" . ?Χ) ("Psi" . ?Ψ) ("Omega" . ?Ω)
  ("alpha" . ?α) ("beta" . ?β) ("gamma" . ?γ)
  ("delta" . ?δ) ("epsilon" . ?ε) ("zeta" . ?ζ)
  ("eta" . ?η) ("theta" . ?θ) ("iota" . ?ι)
  ("kappa" . ?κ) ("lambda" . ?λ) ("mu" . ?μ)
  ("nu" . ?ν) ("xi" . ?ξ) ("omicron" . ?ο)
  ("pi" . ?π) ("rho" . ?ρ) ("sigma" . ?σ)
  ("tau" . ?τ) ("upsilon" . ?υ) ("phi" . ?φ)
  ("chi" . ?χ) ("psi" . ?ψ) ("omega" . ?ω))

in which case you may want to use a custom font for Greek characters:

(dolist (ft (fontset-list))
  (set-fontset-font ft 'greek (font-spec :name "DejaVu Sans Mono")))

Tip: to add multi-character substitutions, you may want to consult issue #201.

Autocompleting symbols and tactics defined externally

The procedure above will give you auto-completion and documentation for tactics, commands, and theorems that you define locally, but not for theorem names and symbols defined in the libraries you load. To get the latter, add the following to your .emacs, before (company-coq-mode):

(setq company-coq-live-on-the-edge t)

Installing from source

Use Cask.

Special thanks

Many thanks to Pierre Courtieu for his work on Proof General, and to Jonathan Leivent and Jason Gross for their tireless bug reports and suggestions!