ocaml / README.itz

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This directory contains files to help editing Caml code, running a
Caml toplevel, and running the Caml debugger under the Gnu Emacs editor.


Ian T Zimmerman <> added indentation to caml mode, beefed
up camldebug to work much like gud/gdb.

Xavier Leroy (, Jerome Vouillon (
camldebug.el is derived from FSF code.


    caml.el         A major mode for editing Caml code in Gnu Emacs
    inf-caml.el     To run a Caml toplevel under Emacs, with input and
                    output in an Emacs buffer.
    camldebug.el    To run the Caml debugger under Emacs.


This package will no longer work with Emacs 18.x. Sorry. You really
should consider upgrading to Emacs 19.


Add the following lines to your .emacs file:

(setq auto-mode-alist (cons '("\\.ml[iylp]?" . caml-mode) auto-mode-alist))
(autoload 'caml-mode "caml" "Major mode for editing Caml code." t)
(autoload 'run-caml "inf-caml" "Run an inferior Caml process." t)
(autoload 'camldebug "camldebug" "Run the Caml debugger." t)

The Caml major mode is triggered by visiting a file with extension .ml,
.mli, .mly. .mll or .mlp, or manually by M-x caml-mode. It gives you the
correct syntax table for the Caml language. For a brief description of
the indentation capabilities, see below under NEWS.

The Caml mode also allows you to run batch Caml compilations from
Emacs (using M-x compile) and browse the errors (C-x `). Typing C-x `
sets the point at the beginning of the erroneous program fragment, and
the mark at the end. Under Emacs 19, the program fragment is
temporarily highlighted.

M-x run-caml starts a Caml toplevel with input and output in an Emacs
buffer named *inferior-caml*. This gives you the full power of Emacs
to edit the input to the Caml toplevel. This mode is based on comint
so you get all the usual comint features, including command history.

After M-x run-caml, typing C-c C-e or M-C-x in a buffer in Caml mode
sends the current phrase (containing the point) to the Caml toplevel,
and evaluates it.

M-x camldebug FILE starts the Caml debugger camldebug on the executable
FILE, with input and output in an Emacs buffer named *camldebug-FILE*.
For a brief description of the commands available in this buffer, see
NEWS below.


Ok, so this is the really important part of this file :-) I took the
original package from the contrib subdirectory of the caml-light
distribution, and hacked on it. First, I added real syntax dependent
indentation to caml mode. Like Xavier has said, it was hard (and I
knew it would be), but I refused to believe it was impossible, partly
because I knew of a Standard ML mode with indentation (written by
Matthew Morley).

Indentation works pretty much like in other programming modes. C-j at
the end of a line starts a new line properly indented. M-C-\ indents
the current region (this may take a while :-)). I incorporated a
slightly different TAB function, one that I use in other modes: if TAB
is pressed while the point is not in line indentation, the line is
indented to the column where point is (instead of just inserting a TAB
character - you can always to that with C-q C-i). This way, you can
indent a line any time, regardless of where the point lies, by hitting
TAB twice in succession. If you don't like this behaviour (but you
should), it's quite easy to add to your startup code like this:

(defun caml-old-style-indent ()
        (if (caml-in-indentation)
                (insert "\t")))

(add-hook 'caml-mode-hook
        (function (lambda ()
                (define-key 'caml-mode-map "\t"

You can customize the appearance of your caml code by twiddling the
variables listed at the start of caml.el. Good luck. :-)

Other news in caml mode are the various caml-insert-*-form commands. I
believe they are self-explanatory - just do a C-h m in a caml buffer
to see what you've got.

The ohter major news is that I changed camldebug mode considerably. I
took many clues from the gud "Grand Unified Debugger" mode distributed
with modern versions of Emacs. The main benefit here is that you can
do debugger commands _from your caml source buffer_. Commands with the
C-c prefix in the debugger buffer have counterparts which do the same
thing (well, a similar thing) in the source buffer, with the C-x C-a

I made the existing debugger commands smarter in that they now attempt
to guess the correct parameter to the underlying camldebug command. A
numeric argument will always override that guess. For example, the
guess for C-c C-b (camldebug-break) is to set a breakpoint at the
current event (which was the only behaviour provided with the old
camldebug.el). But C-u 1 C-c C-b will now send "break 1" to the
camldebug process, setting a break at code address 1.

This also allowed me to add many more commands for which the
underlying camldebug commands require a parameter. The best way to
learn about them is to do C-h m in the camldebug buffer, and then C-h
f for the commands you'll see listed.

Finally, I added command completion. To use it, you'll have to apply
the provided patch to the debugger itself
(contrib/debugger/, and recompile it
(you'll get one warning from the compiler; it is safe to ignore
it). Then hitting TAB in the following situation, for example:

(cdb) pri_

will complete the "pri" to "print".


I don't use X and haven't tested this stuff under the X mode of
emacs. It is entirely possible (though not very probable) that I
introduced some undesirable interaction between X (fontification,
highlighting,...) and caml mode. I will welcome reports of such
problems (see REPORTING below), but I won't be able to do much about
them unless you also provide a patch.

I don't know if the informational messages produced by camldebug are
internationalized. If they are, the debugger mode won't work unless
you set the language to English. The mode uses the messages to
synchronize with camldebug, and looks for fixed Emacs regular
expressions that match them. This may be fixed (if necessary) in a
future release.


In the debugger buffer, it's possible to overflow your mental stack by
asking for help on help on help on help on help on help on help on


Xavier Leroy <> for Caml-light. Used together with the
Emacs interface, it is about the most pleasant programming environment
I've known on any platform.

Eric Raymond <> for gud, which camldebug mode apes.

Barry Warsaw <> for elp, without which I wouldn't have
been able to get the indentation code to perform acceptably.

Gareth Rees <> for suggestions how to speed up
Emacs regular expression search, even if I didn't use them in the end.

Bill Dubuque <> for alerting me to the
necessity of guarding against C-g inside Emacs code which modifies
syntax tables.


Bug reports (preferably with patches), suggestions, donations etc. to:

Ian T Zimmerman           +-------------------------------------------+
Box 13445                 I    With so many executioners available,   I
Berkeley CA 94712 USA     I suicide is a really foolish thing to do.  I      +-------------------------------------------+