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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.

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

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.

Debugger

Version 8.15 introduces a visual debugger for L_tac tactics within CoqIDE. It supports setting breakpoints visually and automatically displaying the stopping point in the source code with "continue", "step over" "step in" and "step out" operations. The call stack and variable values for each stack frame are shown in a new panel.

The debugger is based on the non-visual L_tac debugger. We'd like to eventually support other scripting facilities such as Ltac2.

Since the visual debugger is new in 8.15, you may encounter bugs or usability issues. The behavior and user interface will evolve as the debugger is refined. There are notes on bugs and potential enhancements at the end of this page. Feel free to suggest changes and improvements by opening an issue on GitHub, or contact @jfehrle directly through email, Zulip or Discourse.

Breakpoints

This screenshot shows the debugger stopped at a breakpoint in the L_tac tactic my_tac. Breakpoints are shown with a red background and the stopping point is shown with a dark blue background. Set Ltac Debug. enables stopping in the debugger.

You can control the debugger with function and control keys. Some messages are shown in the Messages panel. You can type debugger commands in that panel when it shows the debug prompt.

The script is not editable while Coq is processing tactics or stopped in the debugger. When Coq is stopped in the debugger (e.g., at a breakpoint), the blue segment in the "in progress" slider at the bottom edge of the window will be stopped at the left hand edge of its range.

The function keys are listed, for the moment, with one exception, in the Debug menu:

Toggle breakpoint (F8)

Position the cursor on the first character of the tactic name in an Ltac construct, then press F8. Press again to remove the breakpoint. F8 is accepted only when all of the coqtop sessions are idle (i.e. at the debug prompt or not processing a tactic or command).

Note that sentences containing a single built-in tactic are not Ltac constructs. A breakpoint on intros., for example, is ignored, while breakpoints on either tactic in intros; idtac. work. A breakpoint on, say, my_ltac_tactic. also works.

Breakpoints on Ltac value_tactics, which compute values without changing the proof context, such as eval, are ignored.

You must set at least one breakpoint in order to enter the debugger.

Continue (F9)

Continue processing the proof. If you're not stopped in the debugger, this is equivalent to "Run to end" (Control End).

Step over (Control ↓)

When stopped in the debugger, execute the next tactic without stopping inside it. If the debugger reaches a breakpoint in the tactic, it will stop. This is the same key combination used for "Forward one command"—if you're stopped in the debugger then it does a "Step over" and otherwise it does a "Forward". Combining the two functions makes it easy to step through a script in a natural way when some breakpoints are set.

Step in (F10)

When stopped in the debugger, if next tactic is an L_tac tactic, stop at the first possible point in the tactic. Otherwise acts as a "step over".

Step out (Shift F10)

When stopped in the debugger, continue and then stop at the first possible point after exiting the current L_tac tactic. If the debugger reaches a breakpoint in the tactic, it will stop.

Break (F11)

Stops the debugger at the next possible stopping point, from which you can step or continue. (Not supported in Windows at this time.)

If you step through idtac "A"; idtac "B"; idtac "C"., you'll notice that the steps for my_tac are:

idtac "A"; idtac "B"; idtac "C"

idtac "A"; idtac "B"

idtac "A"

idtac "B"

idtac "C"

which reflects the two-phase execution process for the tactic ; tactic construct.

Also keep in mind that L_tac backtracking may cause the call stack to revert to a previous state. This may cause confusion. Currently there's no special indication that this has happened.

Call Stack and Variables

The bottom panel shows the call stack and the variables defined for the selected stack frame. Stack frames normally show the name of tactic being executed, the line number and the last component of the filename without the .v suffix. The directory part of the module name is shown when the frame is not in the toplevel script file. For example, make_rewriter:387, AllTactics (Rewriter.Rewriter) refers to the file with the module name Rewriter.Rewriter.AllTactics.

Note: A few stack frames aren't yet displayed in this described format (e.g. those starting with ???) and may be extraneous. In some cases, the tactic name is not shown.

Click on a stack frame or press the Up (↑) or Down (↓) keys to select a stack frame. Coq will jump to the associated code and display the variables for that stack frame. You can select text with the mouse and then copy it to the clipboard with Control-C. Control-A selects the entire stack.

The variables panel uses a tree control to show variables defined in the selected stack frame. To see values that don't fit on a single line, click on the triangle. You can select one or more entries from the tree in the usual way by clicking, shift-clicking and control-clicking on an entry. Control-A selects all entries. Control-C copies the selected entries to the clipboard.

Note: Some variable are not displayed in a useful form. For example, the value shown for tac in a script containing let tac = ltac:(auto) appears only as <genarg:tacvalue>. We hope to address this soon.

The DETACH button moves the debugger panel into a separate window, which will make it easier to examine its contents.

Supported use cases

There are two main use cases for the debugger. They're not very compatible. Instead of showing warning messages or forcing the user to explicitly pick one mode or another, for now it's up to the user to know the limitations and work within them.

The single file case is running the debugger on a single primary script without ever stopping in other secondary scripts. In this case, you can edit the primary script while Coq is not running it nor stopped in the debugger. The position of breakpoints will be updated automatically as you edit the file. It's fine to run the debugger in multiple buffers--you will not be confused. The single-file case is preferable when you can use it.

The multi-file case is when a primary script stops in a secondary script. In this case, breakpoints in the secondary script that move due to script editing may no longer match the locations in the compiled secondary script. The debugger won't stop at these breakpoints as you expect. Also, the code highlighted for stack frames in that script may be incorrect. You will need to re-compile the secondary script and then restart the primary script (Restart, Ctrl-HOME) to get back to a consistent state.

For multi-file debugging, we suggest detaching the Messages, Proof Context and Debugger panels so they are in separate windows. To do so, click on the arrow icon next to "Messages", select "Windows / Detach Proof" from the menu and click on "DETACH" in the Debugger panel. Note that the Debugger panel is initially attached to the Script panel of the toplevel script. Also note that, for now, the "in progress" slider is accurate only when the associated toplevel script panel is visible.

If a debugger instance is stopped in a secondary script, the debugger function keys are directed to the debugger instance associated with the primary script. The debugger doesn't attempt to support multiple instances stopped in the same secondary script. If you have a need to do this, run each debugger instance in a separate CoqIDE process/window.

Note that if you set a breakpoint in a script that may be called by multiple debugger instances, you may inadvertently find you've gotten into unsupported territory.