Editing GAP files and running GAP in Emacs buffers
==================================================
(Written 20 Feb 1993)
The files "gap-mode.el" and "gap-process.el" provide modes for both editing
GAP programs in Emacs and running a GAP session within an Emacs buffer.
Brief installation instructions are given at the end of this document.
Editing GAP files in Emacs
--------------------------
Opening any file ending in ".g" or ".gap" should automatically put you into
gap-mode, the major mode for editing of GAP code. This mode may also be
invoked in any buffer at any time by typing M-x gap-mode.
Once in gap-mode there are some notable changes in the behaviour of Emacs.
Whenever you press return for a new line Emacs will reindent the current
line and auto-indent the new line (this behaviour can be deactivated). At
any time, the TAB key will reindent the current line, `M-q' will reindent
each line in the current region, and `M-C-q' will reindent each line in the
whole buffer.
Gap-mode will add indentation for if..then structures, function definitions
and all looping structures,
for N in [1..10] do
Print ( N );
if N > 5 then
Print ( N^2 );
fi;
od; ,
as well as indenting continued statements (those that cross a line break)
in a number of different ways. For example, it will attempt to match up
each line of a matrix,
x := [ [ 1, 2, 3 ],
[ 4, 5, 6 ],
[ 7, 8, 9 ] ];
and the arguments of a function call,
Print ( a, b, c
d, e, f ); .
There are quite a number of variables that control how gap-mode indentation
behaves. Consult the help for gap-mode by typing `C-h m' for a list of the
variables (and the features of gap-mode in general), and then `C-h v <var>'
for a description of what the variable <var> controls.
Running GAP in an Emacs buffer
------------------------------
Type `M-x gap' to run a GAP process with input and output through an Emacs
buffer. Any text typed at the end of the *gap* buffer will be sent to GAP
when the RETURN key is pressed, and GAP's output will be appended to the
end of the buffer. The mode is based on comint-mode.
Moving back through previous commands is slightly different. Use `M-p' and
`M-n' for previous and next input. The command `M-l' will find the last
input that matches what has already been typed. There are some other
features that are inherited (as these are) by using comint-mode as a base
(see the documentation for gap-process-mode by typing `C-h m' in the *gap*
buffer, and also the help for comint-mode: `C-h f comint-mode').
TAB will complete as usual, except that if there is no unique (partial)
completion then the list of completions will be given immediately in a
separate *Completions* buffer. Similarly the help function `?', which will
ask for a topic (defaulting to the current identifier), will give its
results in a *Help* buffer instead of the *gap* buffer.
In fact, if a GAP process is running in the *gap* buffer and NOT BUSY with
a calculation, then completion and help are also available in the gap
editing mode (gap-mode) by typing `M-TAB' and `M-?' respectively.
When starting up the GAP process, giving a prefix argument to the command
(eg by typing `C-u M-x gap') will cause the contents of the current buffer
to be given to GAP as initial input, and GAP will behave exactly as if you
had typed all the current buffer contents into the new *gap* buffer.
Installation
============
Put the file "gap-mode.el" into a directory in your Emacs lisp load path.
If you wish to run GAP within an Emacs buffer, also put "gap-process.el"
and "comint.el" at the same place. Add the following lines to your ".emacs"
startup file.
----------CUT-HERE----------
;; gap mode
(autoload 'gap-mode "gap-mode" "Gap editing mode" t)
(setq auto-mode-alist (append (list '("\\.g$" . gap-mode)
'("\\.gap$" . gap-mode))
auto-mode-alist))
(autoload 'gap "gap-process" "Run GAP in emacs buffer" t)
(setq gap-executable "/usr/algebra/bin/gap")
(setq gap-start-options (list "-l" "/usr/algebra/gap3.1/lib"
"-m" "2m"))
----------CUT-HERE----------
Change the path to your GAP executable and library appropriately. That
should complete installation!
======================================================================
Michael Smith
Mathematics Research Section
Australian National University.
