Seed7-mode - Emacs support for the Seed7 Programming Language

This is a work-in-progress version of seed7-mode 🚧 . A lot of features are implemented but there's still some areas that need improvements or fixes. Please create a bug report for any problem you detect.

Currently Implemented Features

Display seed-mode version information

The seed7-mode-version command, bound to C-c v in seed7-mode buffers, display the version UTC time stamp of the file in the message area, at bottom of the screen. Use this to verify the version of the seed7-mode.el code you are using.

Please include this information in bug reports.

Customize seed7-mode

Several features of the seed7-mode are customizable. Use the seed7-mode-customize command, bound to C-c C to quickly open the seed7-mode customization buffer.

The command is also accessible from the top menu as can be see here. Once issued it opens the seed7-mode customization buffer.

Use the customization buffer to view or change one or several customizable user-option variables.

Since these control the behaviour of the seed7-mode the changes will only apply to buffers that are then opened in seed7-mode. If you already have a buffer using the mode, change to fundamental-mode and then back to seed7-mode for the changes to take effect..

Syntax highlighting with user-customizable faces.

Font lock syntax highlighting for Seed7 supports different faces for different Seed7 syntactic elements, including various faces for different types of numbers and warning font to identify some syntactic errors in the code, but not all.

See the following example screenshots:

Screenshot	Description
Terminal-mode Emacs	Shows the default highlighting of Seed7 code on Emacs running in a macOS Terminal.
Graphical Emacs	Shows the default highlighting of Seed7 code on a basic GUI Emacs running in a macOS with the default scheme.

Emacs outline minor mode support

The seed7-mode supports the Emacs outline minor mode: collapse and expansion of blocks, where heading is the first line of a declaration block. This allows navigation and code manipulation by headings (blocks).

Screenshot	Description
bas.sd7 outline all collapsed	The prg/bas.sd7 file shown with outline-minor-mode active after executing outline-hide-sublevels
bas.sd7 outline with 2 expanded	The same prg/bas.sd7 file shown with outline-minor-mode active after expanding 2 outlines with outline-show-entry at lines 154 and 369.

Emacs top-level menu support

Provides a Seed7 top level menu entry which provides access to the commands. Here's some examples:

Screenshot	Description
Terminal menu 1	Using the top menu to access Seed7 code browsing inside a terminal Emacs.
Terminal menu 2	The selecting the Seed7 item as a second step in the menu using a terminal Emacs.
GUI Emacs menu	Using macOS GUI Emacs with iMenu to list the functions is the Seed7 file. Unlike Windows and most Linux desktops, the Emacs menu shows up inside the macOS top screen menu by default but it's also possible to make it show inside the Emacs frame as the next screen captures show.
Navigation to structure menu	The menu can be opened inside the frame explicitly with the menu-bar-open command. Here it is showing the navigation listing the structures declared inside prg/bas.sd7
Comments menu	The comments-specific commands.
Template insertion menu	The template insertion commands. These can be expanded easily with <TAB> as described in the Code Template Insertion section.

Support for imenu mode and Speedbar

• Support Emacs imenu mode and Emacs Speedbar for:
  • Seed7 procedures,
  • Seed7 functions,
  • Seed7 interfaces,
  • Seed7 structures,
  • Seed7 enums.

See the following example screenshots:

Screenshot	Description
Terminal Emacs Speedbar	Using Emacs Speedbar to navigate the Seed7/pgm directory, listing function, procedures, structures, etc...
GUI Emacs Speedbar	Using macOS GUI Emacs with Speedbar in a separate GUI frame showing beside the local instance of the PEL Speedbar PDF.
GUI Emacs menu	Using macOS GUI Emacs with iMenu to list the functions is the Seed7 file. Unlike Windows and most Linux desktops, the Emacs menu shows up inside the macOS top screen menu.
Terminal menu 1	Using the top menu to access Seed7 code browsing inside a terminal Emacs.
Terminal menu 2	The selecting the Seed7 item as a second step in the menu using a terminal Emacs.
Terminal Ivy prompt	Instead of using the menu, using a prompt with completion driven by ivy to search and select Seed7 element. Shown inside a terminal Emacs.

Indentation Control / Automatic Indentation

Code indentation is done automatically when the <tab> key is pressed from anywhere on the line, except when used to expand a callable parameter in most cases. Automatic code indentation is also done when the <return> key is pressed.

The auto-fill mode is supported.

The following customizable user-option variables control Seed7 code indentation.

.	Variable	Purpose
.	seed7-auto-indent	Control whether auto-indentation of Seed7 code is active. It is on by default. To disable auto-indentation, set seed7-auto-indent to nil, then disable (by activating fundamental-mode) and re-enable seed7-mode.
.	seed7-indent-width	Number of columns used for each indentation level of Seed7 code. Defaults to 2.
.	indent-tabs-mode	Control whether Emacs inserts ASCII hard TAB characters when indenting. If set to nil Emacs will only use ASCII SPACE characters. If active (set to T or any non-nil value) Emacs will insert ASCII hard TAB character to fill indentation according to the number of columns of indentation required and the number of columns used to render a hard tab (as specified by tab-width). For Seed7 code, the convention is to avoid hard TAB characters in the code, therefore the indent-tab-mode should be turned off to prevent seed7-mode auto-indentation to insert hard TAB characters. Use the untabify command to replace all hard TAB characters in the buffer by the equivalent number of SPACE characters.
.	tab-width	Controls the the column width of a hard TAB on display.

Notes:

• One aspect of the auto indentation logic is that it checks (and extracts) the name of procedure and functions and the return type of the function. The auto-indentation will only work properly once these are identified. This acts as a reminder to fill in the missing parts.
• 🚧 As this code is still under early development please report any problem you may encounter.

Code Template Insertion

Seed7 code templates are inserted at point when the <tab> key is pressed after one of the supported code identifier keywords under specific constraints:

• When point is following one of the keywords from the first group and that is the only word on the current line, or
• when point is following one of the keywords of the second group and is located just before a ) character (with or without a space between point and the closing parenthesis. The second group holds keywords for argument declarations.

After successfully expanding the Seed7 code template, point is located at the first location that must be filled. This location, and the following locations that must be filled, are internally identified by Emacs tempo markers. You can use the tempo-forward-mark and tempo-backward-mark to move point to these markers. The seed7-mode keyboard map binds the <backtab> key to the tempo-forward-mark command. So after expanding a code template, fill the first field and then press <backtab> to move point to the next field.

As mentioned above there are two groups of keywords, listed in the following tables.

First Group -- Statements:

Expand the following keywords when point is located just after any of these keywords, with the keyword being the only word on the current line.

Keyword	Expansion
inc	include statement
const	constant declaration
var	variable declaration
.
proc	procedure declaration
func	function declaration
funcs	short function declaration
.
enum	enum type declaration
struct	struct type declaration
.
case	case statement
if	if statement
ife	if statement with an else clause
ifei	if statement with an elsif clause
ifeie	if statement with an elsif and an else clause
repeat	repeat - until statement
while	while statement
for	for statement
foru	for-until statement
fors	for-step statement
fore	for-each statement
foreu	for-each statement combined with an until condition
forek	for-each-key statement
foreku	for-each-key statement combined with an until condition
fork	for-key statement
forku	for-key statement combined with an until condition
.
bl	Exception handler block
gl	global - end global block.

Second Group -- Argument Declarations

Expand the following keywords with <tab> when point is located just after any of these keywords and before the closing parenthesis of a parameter list.

Keyword	Expansion
in	Declaration of an in-parameter.
inout	Declaration of an inout-parameter.
invar	Declaration of an in-var-parameter.
callbn	Declaration of a call-by-name parameter.
ref	Declaration of a reference-parameter.
val	Declaration of a value-parameter.

Seed7 Specific Abbreviations

Ref:	Abbrevs @ Emacs Manual
Ref:	Abbrev Concepts
Ref:	Examining and Editing Abbrevs

By default, the seed7-support-abbrev-mode user-option is on (non-nil). This makes seed7-mode support Seed7-specific abbreviations that can be automatically expanded when the abbrev-mode is active.

You can expand a set of Seed7 keywords by typing their (system) abbreviation followed by a word-separating character such as <space>, <RET>` or ``; and others. All Seed7 abbreviations are short mnemonic character sequences that start with ;.

Dynamically enable or disable the abbrev-mode with the M-x abbrev-mode command. List the abbreviations with M-x list-abbrevs. You can create other abbreviations and edit them with M-x edit-abbrevs. You cannot change the pre-defined Seed7 system abbreviations via the abbrev commands. However you can change all Seed7 system abbreviations since the list is customizable and defined by the seed7-abbreviations customizable user-option. Of course you can also create your own abbreviations via the abbrev mode commands to complement what is provided by seed7-mode.

While abbrev-mode is active, you can explicitly prevent expansion of the keyword type C-q after the keyword before any white-space or punctuation character.

If you do not want to use Seed7-specific abbreviations, you can change the customization of this user-variable with M-x customize-option RET seed7-support-abbrev-mode turning it off, changing the mode to another major mode (such as fundamental-mode) and re-enabling the seed7-mode. If you Apply and Save the customization, the setting will persist across Emacs sessions.

The list of default supported abbreviations is controlled by the seed7-abbreviations customizable user-option. You can modify the keyword or the expansion of any entry and add or delete entries these via customization. The new values are activated the next time a buffer starts the seed7-mode.

The default abbreviations are shown inside the 8 following tables:

• pragmas
• in-statement keywords
• in-middle statement keywords
• block clause keywords
• predefined types
• predefined constants
• predefined variables
• errinfo values

pragmas

Abbreviation	Expansion
;de	decls
;in	info
;li	library
;msg	message
;na	names
;syn	syntax
;sys	system
;tr	trace

in-statement keywords

Meant to follow the is keyword (but not imposed):

Abbreviation	Expansion
;fo	forward
;n	new
;u	sub

Others:

Abbreviation	Expansion
;no	noop
;ra	raise
;rt	return

in-middle statement keywords

Abbreviation	Expansion
;dt	downto
;exc	exception
;lo	local
;pa	param
;rg	range
;rs	result
;st	step

block clause keywords

Abbreviation	Expansion
;ct	catch
;e	else
;ei	elsif
;o	otherwise
;w	when

predefined types

Abbreviation	Expansion
;a	array
;bi	bigInteger
;br	bigRational
;b3	bin32
;b6	bin64
;bt	bitset
;bo	boolean
;bs	bstring
;ca	category
;c	char
;cf	clib_file
;co	color
;cx	complex
;db	database
;du	duration
;en	enum
;ex	expr
;fi	file
;fs	fileSys
;fl	float
;h	hash
;i	integer
;ob	object
;pro	process
;pr	program
;rat	rational
;rf	reference
;rfl	ref_list
;s	set
;sq	sqlStatement
;sti	string
;stu	struct
;tx	text
;ti	time
;ty	type
;v	void
;pw	PRIMITIVE_WINDOW

predefined constants

Abbreviation	Expansion
;em	empty
;f	FALSE
;inf	Infinity
;t	TRUE

predefined variables

Abbreviation	Expansion
;ck	CONSOLE_KEYBOARD
;gk	GRAPH_KEYBOARD
;kb	KEYBOARD
;sc	STD_CONSOLE
;se	STD_ERR
;si	STD_IN
;sn	STD_NULL
;so	STD_OUT

errinfo values

Abbreviation	Expansion
;ok	OKAY_NO_ERROR
;ae	ACTION_ERROR
;ce	COPY_ERROR
;cre	CREATE_ERROR
;dbe	DATABASE_ERROR
;dse	DESTROY_ERROR
;fe	FILE_ERROR
;ge	GRAPHIC_ERROR
;ie	INDEX_ERROR
;ine	IN_ERROR
;me	MEMORY_ERROR
;ne	NUMERIC_ERROR
;oe	OVERFLOW_ERROR
;re	RANGE_ERROR

Code Navigation Commands

Some of the commands have a built-in key binding in the seed7-key-map but not all of them. The PEL Seed7 support provides more key bindings using function keys.

.	Function	Key Binding	Description
.	seed7-beg-of-defun	C-M-a	Move point backward to beginning of function or procedure. With optional repeat argument.
.	seed7-end-of-defun	C-M-e	Move point backward to beginning of function or procedure. With optional repeat argument.
.	seed7-beg-of-next-defun	C-c C-n	Move point forward to beginning of next function or procedure. With optional repeat argument.
.	seed7-to-block-forward	C-c C-e	Move point forward to the end line of the matching statement: array declaration (from begin to end) block, case statement: Move from case to end case but also across the when sections. enum block any of the for statements: for for-each for-each-key for-key for-step for-until if statement: Move from if to end if, but also when at else or elsif move to the next portion. repeat - until statement struct or while statement. If none is found move to the end of the function or procedure.
.	seed7-to-block-backward	C-c C-a	Move point backward to the beginning line of the matching block or statement (listed above).

Code Navigation Through xref

The seed7-mode supports Emacs xref framework and implement an xref-backend for Seed7 code using the supplied s7xref.sd7 Seed7 program.

The seed7-xref user option, which defaults to s7xref identifies the program that should be used to parse the visited Seed7 file and extract information about all identifiers and operators used by the Seed7n program or library file. See the seed7-xref docstring for more information.

Once this is properly setup, you can use the following xref commands to navigate in Seed7 code.

.	Function	Key Binding	Description
.	xref-find-definitions	M-.	Find the definition of the identifier at point. Move point to it if there is only one candidate. If there are several candidates, display the list with the currently active xref front-end. You can then select the appropriate candidate to jump to its code.
.	xref-go-back	M-,	Go back to the previous position in xref history.

The current implementation does not yet display the signature of the identified candidates. This will be done soon.

There are other xref framework commands. They are not yet implemented to support Seed7. This will also be done.

Code Marking Commands

.	Function	Key Binding	Description
.	seed7-mark-defun	C-M-h	Mark the current function or procedure. With point between two; mark the next one.

Compilation Command

.	Function	Key Binding	Description
.	seed7-compile		Static check Seed7 file visited in current buffer. With optional argument compile it. All resulting warning or errors are shown in a compile-mode buffer.

• The static checking and compilation commands are identified in customizable user options.
• The static checking defaults to s7check and the compilation to s7c.
• To perform static checking of Seed7 files, compile the s7check.sd7 part of seed7 program examples and use the generated executable.

Comment Management Commands

.	Function	Key Binding	Description
.	seed7-toggle-comment-style	C-c ;	Toggle between comments to line-end and block comments. Use comment-dwim and comment-block to create or remove comments of selected style. The default style is selected by seed7-uses-block-comment (off by default), and the comment-style customizable user-options.

Compatibility

The seed7-mode is compatible with:

• Emacs comment-dwim command. The recommended key binding for it is M-;
• Emacs which-function-mode, when active shows the name of the current Seed7 function or procedure in the mode line. It also works with Seed7 actions and forward declarations.
• The iedit package that allows selecting variables inside a specific block, function or procedure.
• The expand-region package to quickly select the current word, block, function/procedure.
• Drew Adam's hide-comnt package which provides the hide/show-comments-toggle command to hide or show all comments.
• The smart-dash-mode is quite useful for typing those pesky underscore characters. With this minor mode active just type a dash (easier type than underscore on most keyboards) and it will insert a underscore inside words or symbols and a dash otherwise.

More commands will be implemented.

How To Install seed7-mode with plain vanilla Emacs

Preliminary notes to new Emacs users

Reference:	The Emacs Initialization File

Emacs can and will use a user initialization file, init.el if it finds one.

• Emacs looks for the init.el file inside the directory identified by the user-emacs-directory variable, one of many variable controls Emacs behaviour.
  • Emacs looks for the following files, in the following order by default:
    • ~/.emacs
    • ~/.emacs.el
    • ~/.emacs.d/init.el
    • ~.config/emacs/init.el
• Once started the name of the Emacs init file is stored inside the value of the user-init-file variable.
• It also stores the name of the Emacs directory inside the user-emacs-directory variable.

Inside Emacs you can see the current value of the above variables by typing the C-h o followed by the name of the variable. For example:

• Type C-h o user-emacs-directory RET; that will open a buffer describing the purpose of this variable and show it's current value. It also has a link to the Emacs Lisp code that defines it (which is part of Emacs and you should not modify).
• Type C-h o user-init-file to show the value of this variable.

The user-emacs-directory identifies the directory where Emacs looks for the init.el file. In Unix-like OS installations it is often set to "~/.emacs.d/". Under Windows it will be located somewhere else.

Changing from ~/.emacs to ~/.emacs.d/init.el

If you have used Emacs default you may be using the ~/.emacs file for your Emacs init file.

• Using a complete directory to hold your Emacs initialization file and other Emacs related files, like the downloaded packages, your spelling dictionaries, your persistent customization, etc...
• To get Emacs use the ~/.emacs.d/init.el file instead:
  • Create the ~/.emacs.d directory,
  • Move your ~/.emacs or ~/.emacs.el file to ~/.emacs.d/init.el.
  • When you restart Emacs, check the value of user-emacs-directory and user-init-file; they should reflect the new location.

Install seed7-mode for plain-vanilla Emacs

Make sure your Emacs initialization file is stored inside the ~/.emacs.d directory and is ~/.emacs.d/init.el. If this is not the case read the previous section. Once this is done proceed with the following:

• 1: Create the utils sub-directory to store stand-alone utilities Emacs lisp files like seed7-mode.el. That directory should be located inside the directory identified by Emacs user-emacs-directory:

  • Under Unix-like OS, for example, you would normally create the ~/.emacs.d/utils directory.

• 2: Create the init.el file if it does not exists:

  • Emacs user-emacs-directory identifies the directory where the init.el file should be located.
    • Under Unix-like OS, the file is normally ~/.emacs.d/init.el
  • Create the file if it does not already exist.

• 3: Update init.el: write code to find files in utils and auto-load seed7-mode

  • Inside your init.el file, write the following code:

  ;;; -*-lexical-binding: t; -*-
  
  (push (expand-file-name "utils" user-emacs-directory) load-path)
  (autoload 'seed7-mode "seed7-mode" nil :interactive)
  (add-to-list 'auto-mode-alist '("\\.s\\(d7\\|7i\\)\\'" . seed7-mode))

  • The first line activates lexical-binding. It must be the very first line of the file.
  • The other lines can be anywhere, but must be executed (in case you have some conditional logic).

• 4: Download seed7_mode.el file and copy it in the utils directory

  • The utils directory is the one you created above.

• 5: Byte compile seed7-mode.el

  • Open Emacs and edit (visit) the seed7-mode.el file located in your utils directory.
  • Byte compile it by typing the following command: M-x emacs-lisp-byte-compile-and-load

  Byte compiling is not absolutely necessary but it will verify that everything is ok inside the file and will also speed up Emacs startup. Just remember to byte-compile that file every time you modify it, otherwise Emacs will complain that it's using a byte-compile file that is older than the source file.

How To update seed7-mode in plain Emacs

To update to a later revision,

• Erase the seed7-mode.el and seed7-mode.elc files from the utils directory where you stored them.
• Download the new revision in the same directory.
• Byte-compile the new file as described in the previous section.

How to install and use seed7-mode with PEL

You can also use my PEL Emacs project which deals with all installation and control details of several packages including this seed7-mode.

• First install PEL as described in the PEL manual
• To activate the installation and activation of the seed7-mode package you must set the PEL user-option for Seed7: pel-use-seed7 to the value t (which is one of the possible true values in Emacs Lisp).
  • Once PEL is installed, use the C-h o pel-use-seed7 RET key sequence to open the customization buffer to set this user option. Then close Emacs and restart it. PEL will download and install the file in your ~/.emacs.d/utils directory.
  • Open a Seed7 file, PEL provides extra command key bindings for Seed7 under the F12 key prefix.
    • See the PEL Seed7 PDF for more information about PEL Seed7 Support.
    • The PEL Index PDF has links to several other PDF files on various Emacs-specific topics.

How to Update Seed7-Mode with PEL

With PEL, updating is a little simpler: just delete your ~/.emacs.d/utils/seed7-mode.* files and restart Emacs; it will download the new version and byte-compile it.

Future

Once this code is stable I will add the logic to make it a proper Emacs package and probably will include it under MELPA. But the code is far from being ready for that.

Any help, questions, suggestions are welcome!