SML mode is a major mode for Emacs for editing Standard ML. It has some novel bugs, and some nice features:
|automatically determines if it is used in a case or fun construct, and indents the next line as appropriate, inserting
=>or the name of the function.
Contributions to the package are welcome. I have limited time to work on this project, but I will gladly add any code that you contribute to me to this package.
Although the history of sml-mode is obscure, it seems that the following persons have made contributions to sml-mode:
With luck your system administrator will have installed SML mode somewhere convenient, so it will just magically all work—you can skip the rest of this getting started section. Otherwise you will need to tell Emacs where to find all the SML mode .el files, and when to use them. The where is addressed by locating the Lisp code on your Emacs Lisp load path—you may have to create a directory for this, say /home/mjm/elisp, and then insert the following lines in your /home/mjm/.emacs file:
(add-to-list 'load-path "/home/mjm/elisp") (autoload 'sml-mode "sml-mode" "Major mode for editing SML." t) (autoload 'run-sml "sml-proc" "Run an inferior SML process." t)
The first line adjusts Emacs' internal search path so it can locate the Lisp source you have copied to that directory; the second and third lines tell Emacs to load the code automatically when it is needed. You can then switch any Emacs buffer into SML mode by entering the command
It is usually more convenient to have Emacs automatically place the buffer in SML mode whenever you visit a file containing ML programs. The simplest way of achieving this is to put something like
(add-to-list 'auto-mode-alist '("\\.\\(sml\\|sig\\)\\'" . sml-mode))
also in your .emacs file. Subsequently (after a restart), any files with these extensions will be placed in SML mode buffers when you visit them.
You may want to pre-compile the sml-*.el files (M-x byte-compile-file) for greater speed—byte compiled code loads and runs somewhat faster.
You're reading it. Apart from the on-line info tree (C-h i is the
Emacs key to enter the
info system—you should follow the brief
tutorial if this is unfamiliar), there are further details on specific
commands in their documentation strings. Only the most useful
SML mode commands are documented in the info tree: to find out more
use Emacs' help facilities.
Briefly, to get help on a specific function use C-h f and enter
the command name. All (almost all, then) SML mode commands begin
sml-, so if you type this and press <TAB> (for
completion) you will get a list of all commands. Another way is to use
C-h a and enter the string
sml. This is command apropos; it
will list all commands with that sub-string in their names, and any key
binding they may have in the current buffer. Command apropos gives a
one-line synopsis of what each command does.
Some commands are also variables—such things are allowed in Lisp, if not in ML! See Command Index, for a list of (info) documented functions. See Variable Index, for a list of user settable variables to control the behaviour of SML mode.
Before accessing this information on-line from within Emacs you may have
to set the variable
sml-mode-info. Put in your .emacs file
(setq sml-mode-info "/home/mjm/info/sml-mode.info")
When different from the default this variable should be a string giving the absolute name of the .info file. Then C-c C-i in SML mode (i.e., the command M-x sml-mode-info) will bring up the manual. This help is also accessible from the menu. (Resetting this variable will not be necessary if your site administrator has been kind enough to install SML mode and its attendant documentation in the Emacs hierarchy.)
Now SML mode provides just a few additional editing commands. Most of the work has gone into implementing the indentation algorithm which, if you think about it, has to be complicated for a language like ML. See Indentation Defaults, for details on how to control some of the behaviour of the indentation algorithm. Principal goodies are the `electric pipe' feature, and the ability to insert common SML forms (macros or templates).
This switches a buffer into SML mode. This is a major mode in Emacs. To get out of SML mode the buffer's major mode must be set to something else, like text-mode. See Getting Started, for details on how to set this up automatically when visiting an SML file.
Emacs is all hooks of course. A hook is a variable: if the variable is non-nil it binds a list of Emacs Lisp functions to be run in some order (usually left to right). You can customise SML mode with these hooks:
This is run every time a new SML mode buffer is created (or if you type M-x sml-mode). This is one place to put your preferred key bindings. See Configuration, for some examples.
ML is a complicated language to parse, let alone compile. The indentation algorithm is a little wooden (for some tastes), and the best advice is not to fight it! There are several variables that can be adjusted to control the indentation algorithm (see Customising SML Mode, below).
Further indentation commands that Emacs provides (generically, for all modes) that you may like to recall:
On <LFD> by default. Insert a newline, then indent according to the major mode. See Indentation for Programs, for details.
On C-x <TAB> by default. Moves all lines in the region right by its argument (left, for negative arguments). See Indentation.
On M-; by default. Indent this line's comment to comment column, or insert an empty comment. See Comment Commands.
On M-<LFD> by default. Break line at point and indent, continuing comment if within one. See Multi-Line Comments.
As with other language modes, M-; gives you a comment at the end
of the current line. The column where the comment starts is determined
by the variable
comment-column—default is 40, but it can be
set-comment-column (on C-x ; by default).
Electric keys are generally pretty irritating, so those provided by SML mode are fairly muted. The only truly electric key is ;, and this has to be enabled to take effect.
Key: M-| When the point is in a `case' statement this opens a new line, indents and inserts
| =>leaving point just before the double arrow; if the enclosing construct is a `fun' declaration, the newline is indented and the function name copied at the appropriate column. Generally, try it whenever a
|is wanted—you'll like it!
If this variable is
sml-electric-semijust inserts a semi-colon, otherwise it inserts a semi-colon and a newline, and indents the newline for SML.
Key: C-c <RET> Interactive short-cut to insert common ML forms (a.k.a. macros, or templates). Recognised forms are `let', `local', `case', `abstype', `datatype', `signature', `structure', and `functor'. Except for `let' and `local', these will prompt for appropriate parameters like functor name and signature, etc.. This command prompts in the mini-buffer, with completion.
By default C-c <RET> will insert at point, with the indentation of the current column; if you give a prefix argument (i.e., C-u C-c <RET>) the command will insert a newline first, indent, and then insert the template.
sml-insert-form is also extensible: see Configuration for
Several variables try to control the indentation algorithm and other features of SML mode. Most of them are still in flux so they are not described here yet. If the default values are not acceptable you can set these variables permanently in your .emacs file. See Configuration, for details and examples.
The most useful feature of SML mode is that it provides a convenient interface to the compiler. How serious users of ML put up with a teletype interface to the compiler is beyond me... but perhaps there are other interfaces to compilers that require one to part with serious money. Such remarks can quickly become dated—in this case, let's hope so!
Anyway, SML mode provides an interaction mode,
inferior-sml-mode, where the compiler runs in a separate buffer
in a window or frame of its own. You can use this buffer just like a
terminal, but it's usually more convenient to mark some text in the
SML mode buffer and have Emacs communicate with the sub-process. The
features discussed below are syntax-independent, so they should work
with a wide range of ML-like tools and compilers. See Process Defaults, for some hints.
inferior-sml-mode is a specialisation of the comint
package that comes with Emacs and XEmacs.
Start your favourite ML compiler with the command
This creates a process interaction buffer that inherits some key bindings from SML mode and from comint (see Shell Mode). Starting the ML compiler adds some functions to SML mode buffers so that program text can be communicated between editor and compiler (see ML Interaction).
The name of the ML compiler is the first thing you should know how to specify:
The program to run as ML. You might need to specify the full path name of the program.
Useful for Poly/ML users who may supply a database file, or others who have wrappers for setting various options around the command to run the compiler. Moscow ML people might set this to
"-P full", etc..
sml-program-name is a string holding the name
of the program as you would type it at the shell. You
can always choose a program different to the default by invoking
C-u M-x run-sml
With the prefix argument Emacs will prompt for the command name and any command line arguments to pass to the compiler. Thereafter Emacs will use this new name as the default, but for a permanent change you should set this in your .emacs with, e.g.:
(setq sml-program-name "nj-sml")
Launches ML as an inferior process in another buffer; if an ML process already exists, just switch to the process buffer. A prefix argument allows you to edit the command line to specify the program, and any command line options.
M-x run-sml runs
inferior-sml-mode-hookhooks in that order, but after the compiler is started. Use
inferior-sml-mode-hookto set any
comintbuffer-local configurations for SML mode you like.
Key: C-c C-s Switch from the SML buffer to the interaction buffer. By default point will be placed at the end of the process buffer, but a prefix argument will leave point wherever it was before. If you try C-c C-s before an ML process has been started, you'll just get an error message to the effect that there's no current process buffer.
When started, the ML compiler's default working directory is the current buffer's default directory. This command allows the working directory to be changed, if the compiler can do this. The variable
sml-cd-commandspecifies the compiler command to invoke (see Process Defaults).
Several commands are defined for sending program fragments to the running compiler. Each of the following commands takes a prefix argument that will switch the input focus to the process buffer afterwards (leaving point at the end of the buffer):
Key: C-c C-l Send a `use file' command to the current ML process. The variable
sml-use-commandis used to define the correct template for the command to invoke (see Process Defaults). The default file is the file associated with the current buffer, or the last file loaded if you are in the interaction buffer.
SML mode provides one customisable function for locating the source
position of errors reported by the compiler. This should work whether
use "puzzle.sml"; into the interaction buffer, or use
one of the mechanisms provided for sending programs directly to the
compiler—see ML Interaction.
Key: C-x` Jump to the source location of the next error reported by the compiler. All the usual error-navigation commands are available, see see Compilation Mode.
The process interaction code is independent of the compiler used, deliberately, so SML mode will work with a variety of ML compilers and ML-based tools. There are therefore a number of variables that may need to be set correctly before SML mode can speak to the compiler. Things are by default set up for Standard ML of New Jersey, but switching to a new system is quite easy.
Use file command template. Emacs will replace the
%swith a file name. Note that Emacs requires double quote characters inside strings to be quoted with a backslash.
Compiler command to change the working directory. Not all ML systems support this feature (well, Edinburgh (core) ML didn't), but they should.
Matches the ML compiler's prompt: comint uses this for various purposes.
To customise error reportage for different ML compilers you need to set
two further variables before
next-error can be useful:
Alist that specifies how to match errors in compiler output. Each elt has the form (REGEXP FILE-IDX LINE-IDX [COLUMN-IDX FILE-FORMAT...]) If REGEXP matches, the FILE-IDX'th subexpression gives the file name, and the LINE-IDX'th subexpression gives the line number. If COLUMN-IDX is given, the COLUMN-IDX'th subexpression gives the column number on that line. If any FILE-FORMAT is given, each is a format string to produce a file name to try; %s in the string is replaced by the text matching the FILE-IDX'th subexpression.
This (sort of pedagogic) section gives more information on how to configure SML mode: menus, key bindings, hooks and highlighting are discussed, along with a few other random topics.
One way to set SML mode variables (see Indentation Defaults), and other defaults, is through the
sml-mode-hook in your .emacs. A simple example:
(defun my-sml-mode-hook () "Local defaults for SML mode" (setq sml-indent-level 2) ; conserve on horizontal space (setq words-include-escape t) ; \ loses word break status (setq indent-tabs-mode nil)) ; never ever indent with tabs (add-hook 'sml-mode-hook 'my-sml-mode-hook)
The body of
my-sml-mode-hook is a sequence of assignments. In this
case it is not really necessary to set
sml-indent-level in a hook
because this variable is global (most SML mode variables are). With
(setq sml-indent-level 2)
anywhere in your .emacs file. The variable
automatically made local to the current buffer whenever it is set
explicitly, so it must be set in a hook if you always want
SML mode to behave like this.
Another hook is
inferior-sml-mode-hook. This can be used to
control the behaviour of the interaction buffer through various
variables meaningful to comint-based packages:
(defun my-inf-sml-mode-hook () "Local defaults for inferior SML mode" (add-hook 'comint-output-filter-functions 'comint-truncate-buffer) (setq comint-scroll-show-maximum-output t) (setq comint-input-autoexpand nil)) (add-hook 'inferior-sml-mode-hook 'my-inf-sml-mode-hook)
Again, the body is a sequence of assignments. Unless you run several ML
compilers simultaneously under one Emacs, this hook will normally only
get run once. You might want to look up the documentation (C-h v
and C-h f) for these buffer-local
Customisation (in Emacs) usually entails putting favourite commands on
easily remembered keys. Two `keymaps' are defined in SML mode: one
is effective in program text buffers (
sml-mode-map) and the other
is effective in interaction buffers (
The initial design ensures that (many of) the default key bindings from
the former keymap will also be available in the latter (e.g.,
Type C-h m in an SML mode buffer to find the default key bindings (and similarly in an ML interaction buffer), and use the hooks provided to install your preferred key bindings. Given that the keymaps are global (variables):
(defun my-sml-mode-hook () "Global defaults for SML mode" (define-key sml-mode-map "\C-cd" 'sml-cd)) (add-hook 'sml-mode-hook 'my-sml-mode-hook)
This has the effect of binding
sml-cd to the key C-c d.
If you want the same behaviour from C-c d in the ML buffer:
(defun my-inf-sml-mode-hook () "Global defaults for inferior SML mode" (define-key inferior-sml-mode-map "\C-cd" 'sml-cd) ;; NB. for SML/NJ '96 (setq sml-cd-command "OS.FileSys.chDir \"%s\"")) (add-hook 'inferior-sml-mode-hook 'my-inf-sml-mode-hook)
There is nothing to stop you rebuilding the entire keymap for
SML mode and the ML interaction buffer in your .emacs of
course: SML mode won't define
inferior-sml-mode-map if you have already done so.
Highlighting is very handy for picking out keywords in the program text, spotting misspelled kewyords, and, if you have Emacs' ps-print package installed (you usually do these days), obtaining pretty, even colourful code listings—quite properly for your colourful ML programs.
The indentation scheme (strangely enough) also relies on the highlighting code to properly handle nested comments, which is yet another reason to turn on highlighting. To turn on highlighting, use either of:
M-x font-lock-mode (add-hook 'sml-mode-hook 'turn-on-font-lock) (global-font-lock-mode 1)
The first will turn it on in the current buffer. The second will turn it on in all sml-mode buffers. The last will turn it on everywhere. This is valid for Emacs but maybe not for XEmacs. Check font-lock documentation if you encounter problems.
You can indeed.
sml-insert-formis extensible so all you need to do is create the macros yourself. Define a keybord macro (C-x ( <something> C-x )) and give it a suitable name:
sml-addto-forms-alistprompts for a name, say
NAME, and binds the macro
sml-form-NAME. Thereafter C-c <RET> NAME will insert the macro at point, and C-u C-c <RET> NAME will insert the macro after a
newline-and-indent. If you want to keep your macros from one editing session to the next, go to your .emacs file and call
insert-kbd-macro; you'll need to add
(defun my-sml-mode-hook () "Global defaults for SML mode" ;; whatever else you do (add-to-list 'sml-forms-alist '("NAME" . FUNCTION)))
If you want to create templates like `case' that prompt for parameters
you'll have to do some Lisp programming. The
skeleton package is
a good stating point. Better yet, you can reuse the wrappers used by
sml-mode itself in your sml-mode-hook:
(add-hook 'sml-mode-hook (lambda () (sml-def-skeleton "case" "Case expr: " str " of" \n _ " => ")))
This will redefine `case' in order to leave the `of' on the first line.
See the documentation of
skeleton-insert to get a better
understanding of how this works.
Ah, yes, of course, but this manual will not tell you how.
Sure, just rename the `*sml*' buffer and then use
Not much really. Just add the right regular expressions to
sml-error-regexp-alistand that should be all.
inferior-sml-mode: Interaction Mode
next-error: Tracking Errors
run-sml: Running ML
sml-cd: Running ML
sml-electric-pipe: Magic Insertion
sml-electric-semi: Magic Insertion
sml-electric-space: Magic Insertion
sml-indent-level: SML Mode Defaults
sml-insert-form: Magic Insertion
sml-load-file: ML Interaction
sml-mode-info: Getting Help
sml-send-buffer: ML Interaction
sml-send-region: ML Interaction
sml-send-region-and-go: ML Interaction
switch-to-sml: Running ML
inferior-sml-mode-hook: Running ML
sml-cd-command: Process Defaults
sml-default-arg: Running ML
sml-electric-semi-mode: Magic Insertion
sml-error-regexp-alist: Process Defaults
sml-indent-level: SML Mode Defaults
sml-mode-info: Getting Help
sml-program-name: Running ML
sml-prompt-regexp: Process Defaults
sml-use-command: Process Defaults