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OCaml Emacs mode

The files in this archive define a caml-mode for Emacs, for editing OCaml programs, as well as an inferior-caml-mode, to run a toplevel.

Caml-mode supports indentation, compilation and error retrieving, sending phrases to the toplevel. Moreover support for hilit, font-lock and imenu was added.

This package is based on the original caml-mode for caml-light by Xavier Leroy, extended with indentation by Ian Zimmerman. For details see README.itz, which is the README from Ian Zimmerman's package.



The easiest way of installing this package is through NonGNU ELPA or MELPA (set it up). Just run M-x package-list-packages.


Alternatively, you can use OPAM and install caml-mode and user-setup:

opam install caml-mode user-setup

Manual instllation

To use this package, just put the .el files in your Emacs load path, and add the following lines in your Init File.

(add-to-list 'auto-mode-alist '("\\.ml[iylp]?$" . caml-mode))
(autoload 'caml-mode "caml" "Major mode for editing OCaml code." t)
(autoload 'run-caml "inf-caml" "Run an inferior OCaml process." t)
(autoload 'camldebug "camldebug" "Run ocamldebug on program." t)
(add-to-list 'interpreter-mode-alist '("ocamlrun" . caml-mode))
(add-to-list 'interpreter-mode-alist '("ocaml" . caml-mode))

or put the .el files in, eg. /usr/share/emacs/site-lisp/caml-mode/ and add the following line in addtion to the four lines above:

(add-to-list 'load-path "/usr/share/emacs/site-lisp/caml-mode")

To install the mode itself, edit the Makefile and do

% make install

To install ocamltags, do

% make install-ocamltags

To use highlighting capabilities, add one of the following two lines to your Init File. The second one works better on recent versions of Emacs.

(if window-system (require 'caml-hilit))
(if window-system (require 'caml-font))

caml.el and inf-caml.el can be used collectively, but it might be a good idea to copy caml-hilit.el or caml-font.el to you own directory, and edit it to your taste and colors.

Main key bindings

TAB indent current line
M-C-q indent phrase
M-C-h mark phrase
C-c C-a switch between interface and implementation
C-c C-c compile (usually make)
C-x` goto next error (also mouse button 2 in the compilation log)

Once you have started caml by M-x run-caml:

M-C-x send phrase to inferior caml process
C-c C-r send region to inferior caml process
C-c C-s show inferior caml process
C-c` goto error in expression sent by M-C-x

For other bindings, see C-h b.

Some remarks about the style supported

Since OCaml's syntax is very liberal (more than 100 shift-reduce conflicts with yacc), automatic indentation is far from easy. Moreover, you expect the indentation to be not purely syntactic, but also semantic: reflecting the meaning of your program.

This mode tries to be intelligent. For instance some operators are indented differently in the middle and at the end of a line (thanks to Ian Zimmerman). Also, we do not indent after if .. then .. else, when else is on the same line, to reflect that this idiom is equivalent to a return instruction in a more imperative language, or after the in of let .. in, since you may see that as an assignment.

However, you may want to use a different indentation style. This is made partly possible by a number of variables at the beginning of caml.el. Try to set them. However this only changes the size of indentations, not really the look of your program. This is enough to disable the two idioms above, but to do anything more you will have to edit the code... Enjoy!

This mode does not force you to put ;; in your program. This means that we had to use a heuristic to decide where a phrase starts and stops, to speed up the code. A phrase starts when any of the keywords let, type, class, module, functor, exception, val, external, appears at the beginning of a line. Using the first column for such keywords in other cases may confuse the phrase selection function.