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Coq Integrated Development Environment

The Coq Integrated Development Environment is a graphical tool, to be used as a user-friendly replacement to coqtop. Its main purpose is to allow the user to navigate forward and backward into a Coq file, executing corresponding commands or undoing them respectively.

CoqIDE is run by typing the command coqide on the command line. Without argument, the main screen is displayed with an “unnamed buffer”, and with a filename as argument, another buffer displaying the contents of that file. Additionally, coqide accepts the same options as coqtop, given in The Coq commands, the ones having obviously no meaning for CoqIDE being ignored.

CoqIDE main screen

A sample CoqIDE main screen, while navigating into a file Fermat.v, is shown in the figure CoqIDE main screen. At the top is a menu bar, and a tool bar below it. The large window on the left is displaying the various script buffers. The upper right window is the goal window, where goals to be proven are displayed. The lower right window is the message window, where various messages resulting from commands are displayed. At the bottom is the status bar.

Managing files and buffers, basic editing

In the script window, you may open arbitrarily many buffers to edit. The File menu allows you to open files or create some, save them, print or export them into various formats. Among all these buffers, there is always one which is the current running buffer, whose name is displayed on a background in the processed color (green by default), which is the one where Coq commands are currently executed.

Buffers may be edited as in any text editor, and classical basic editing commands (Copy/Paste, …) are available in the Edit menu. CoqIDE offers only basic editing commands, so if you need more complex editing commands, you may launch your favorite text editor on the current buffer, using the Edit/External Editor menu.

Interactive navigation into Coq scripts

The running buffer is the one where navigation takes place. The toolbar offers five basic commands for this. The first one, represented by a down arrow icon, is for going forward executing one command. If that command is successful, the part of the script that has been executed is displayed on a background with the processed color. If that command fails, the error message is displayed in the message window, and the location of the error is emphasized by an underline in the error foreground color (red by default).

In the figure CoqIDE main screen, the running buffer is Fermat.v, all commands until the Theorem have been already executed, and the user tried to go forward executing Induction n. That command failed because no such tactic exists (names of standard tactics are written in lowercase), and the failing command is underlined.

Notice that the processed part of the running buffer is not editable. If you ever want to modify something you have to go backward using the up arrow tool, or even better, put the cursor where you want to go back and use the goto button. Unlike with coqtop, you should never use Undo to go backward.

There are two additional buttons for navigation within the running buffer. The "down" button with a line goes directly to the end; the "up" button with a line goes back to the beginning. The handling of errors when using the go-to-the-end button depends on whether Coq is running in asynchronous mode or not (see Chapter Asynchronous and Parallel Proof Processing). If it is not running in that mode, execution stops as soon as an error is found. Otherwise, execution continues, and the error is marked with an underline in the error foreground color, with a background in the error background color (pink by default). The same characterization of error-handling applies when running several commands using the "goto" button.

If you ever try to execute a command that runs for a long time and would like to abort it before it terminates, you may use the interrupt button (the white cross on a red circle).

There are other buttons on the CoqIDE toolbar: a button to save the running buffer; a button to close the current buffer (an "X"); buttons to switch among buffers (left and right arrows); an "information" button; and a "gears" button.

The "gears" button submits proof terms to the Coq kernel for type checking. When Coq uses asynchronous processing (see Chapter Asynchronous and Parallel Proof Processing), proofs may have been completed without kernel-checking of generated proof terms. The presence of unchecked proof terms is indicated by Qed statements that have a subdued being-processed color (light blue by default), rather than the processed color, though their preceding proofs have the processed color.

Notice that for all these buttons, except for the "gears" button, their operations are also available in the menu, where their keyboard shortcuts are given.

Commands and templates

The Templates menu allows using shortcuts to insert commands. This is a nice way to proceed if you are not sure of the syntax of the command you want.

Moreover, from this menu you can automatically insert templates of complex commands like Fixpoint that you can conveniently fill afterwards.

Queries

CoqIDE queries

We call query any command that does not change the current state, such as Check, Search, etc. To run such commands interactively, without writing them in scripts, CoqIDE offers a query pane. The query pane can be displayed on demand by using the View menu, or using the shortcut F1. Queries can also be performed by selecting a particular phrase, then choosing an item from the Queries menu. The response then appears in the message window. The image above shows the result after selecting of the phrase Nat.mul in the script window, and choosing Print from the Queries menu.

Compilation

The Compile menu offers direct commands to:

  • compile the current buffer

  • run a compilation using make

  • go to the last compilation error

  • create a Makefile using coq_makefile.

Customizations

You may customize your environment using the menu Edit/Preferences. A new window will be displayed, with several customization sections presented as a notebook.

The first section is for selecting the text font used for scripts, goal and message windows.

The second and third sections are for controlling colors and style of the three main buffers. A predefined Coq highlighting style as well as standard GtkSourceView styles are available. Other styles can be added e.g. in $HOME/.local/share/gtksourceview-3.0/styles/ (see the general documentation about GtkSourceView for the various possibilities). Note that the style of the rest of graphical part of CoqIDE is not under the control of GtkSourceView but of GTK+ and governed by files such as settings.ini and gtk.css in $XDG_CONFIG_HOME/gtk-3.0 or files in $HOME/.themes/NameOfTheme/gtk-3.0, as well as the environment variable GTK_THEME (search on internet for the various possibilities).

The fourth section is for customizing the editor. It includes in particular the ability to activate an Emacs mode named micro-Proof-General (use the Help menu to know more about the available bindings).

The next section is devoted to file management: you may configure automatic saving of files, by periodically saving the contents into files named #f# for each opened file f. You may also activate the revert feature: in case a opened file is modified on the disk by a third party, CoqIDE may read it again for you. Note that in the case you edited that same file, you will be prompted to choose to either discard your changes or not. The File charset encoding choice is described below in Character encoding for saved files.

The Externals section allows customizing the external commands for compilation, printing, web browsing. In the browser command, you may use %s to denote the URL to open, for example: firefox -remote "OpenURL(%s)".

Notice that these settings are saved in the file coqiderc in the coq subdirectory of the user configuration directory which is the value of $XDG_CONFIG_HOME if this environment variable is set and which otherwise is $HOME/.config/.

A GTK+ accelerator keymap is saved under the name coqide.keys in the same coq subdirectory of the user configuration directory. It is not recommended to edit this file manually: to modify a given menu shortcut, go to the corresponding menu item without releasing the mouse button, press the key you want for the new shortcut, and release the mouse button afterwards. If your system does not allow it, you may still edit this configuration file by hand, but this is more involved.

Using Unicode symbols

CoqIDE is based on GTK+ and inherits from it support for Unicode in its text windows. Consequently a large set of symbols is available for notations. Furthermore, CoqIDE conveniently provides a simple way to input Unicode characters.

Displaying Unicode symbols

You just need to define suitable notations as described in the chapter Syntax extensions and notation scopes. For example, to use the mathematical symbols ∀ and ∃, you may define:

Notation "∀ x .. y , P" := (forall x, .. (forall y, P) ..)   (at level 200, x binder, y binder, right associativity)   : type_scope.
Notation "∃ x .. y , P" := (exists x, .. (exists y, P) ..)   (at level 200, x binder, y binder, right associativity)   : type_scope.

There exists a small set of such notations already defined, in the file utf8.v of Coq library, so you may enable them just by Require Import Unicode.Utf8 inside CoqIDE, or equivalently, by starting CoqIDE with coqide -l utf8.

However, there are some issues when using such Unicode symbols: you of course need to use a character font which supports them. In the Fonts section of the preferences, the Preview line displays some Unicode symbols, so you could figure out if the selected font is OK. Related to this, one thing you may need to do is choosing whether GTK+ should use antialiased fonts or not, by setting the environment variable GDK_USE_XFT to 1 or 0 respectively.

Bindings for input of Unicode symbols

CoqIDE supports a builtin mechanism to input non-ASCII symbols. For example, to input π, it suffices to type \pi then press the combination of key Shift+Space (default key binding). Often, it suffices to type a prefix of the latex token, e.g. typing \p then Shift+Space suffices to insert a π.

For several symbols, ASCII art is also recognized, e.g. \-> for a right arrow, or \>= for a greater than or equal sign.

A larger number of latex tokens are supported by default. The full list is available here: https://github.com/coq/coq/blob/master/ide/coqide/default_bindings_src.ml

Custom bindings may be added, as explained further on.

The mechanism is active by default, but can be turned off in the Editor section of the preferences.

Note

It remains possible to input non-ASCII symbols using system-wide approaches independent of CoqIDE.

Adding custom bindings

To extend the default set of bindings, create a file named coqide.bindings and place it in the same folder as coqide.keys. This would be the folder $XDG_CONFIG_HOME/coq, defaulting to ~/.config/coq if XDG_CONFIG_HOME is unset. The file coqide.bindings should contain one binding per line, in the form \key value, followed by an optional priority integer. (The key and value should not contain any space character.)

Example

Here is an example configuration file:

\par ||
\pi π 1
\le ≤ 1
\lambda λ 2
\lambdas λs

Above, the priority number 1 on \pi indicates that the prefix \p should resolve to \pi, and not to something else (e.g. \par). Similarly, the above settings ensure than \l resolves to \le, and that \la resolves to \lambda.

It can be useful to work with per-project binding files. For this purpose CoqIDE accepts a command line argument of the form -unicode-bindings file1,file2,...,fileN. Each of the file tokens provided may consists of one of:

  • a path to a custom bindings file,

  • the token default, which resolves to the default bindings file,

  • the token local, which resolves to the coqide.bindings file stored in the user configuration directory.

Warning

If a filename other than the first one includes a "~" to refer to the home directory, it won't be expanded properly. To work around that issue, one should not use comas but instead repeat the flag, in the form: -unicode-bindings file1 .. -unicode-bindings fileN.

Note

If two bindings for a same token both have the same priority value (or both have no priority value set), then the binding considered is the one from the file that comes first on the command line.

Character encoding for saved files

In the Files section of the preferences, the encoding option is related to the way files are saved.

If you have no need to exchange files with non-UTF-8 aware applications, it is better to choose the UTF-8 encoding, since it guarantees that your files will be read again without problems. (This is because when CoqIDE reads a file, it tries to automatically detect its character encoding.)

If you choose something else than UTF-8, then missing characters will be written encoded by x{....} or x{........} where each dot is an hexadecimal digit: the number between braces is the hexadecimal Unicode index for the missing character.