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#+TITLE: swankr: SWANK (and SLIME) for R
#+AUTHOR: Christophe Rhodes
#+EMAIL: csr21@cantab.net
* Introduction
This is swankr, an implementation of the swank[fn:1] protocol for
R[fn:2]. While the coverage of swank protocol functions is
currently limited, enough is implemented for swankr to be useful: at
the very minimum, it can be used to develop and extend itself.
** Relationship with ESS
Emacs Speaks Statistics[fn:3] provides an interaction mode for R
(among other statistical software packages), including an interface
to R's toplevel, and keybindings to send input to R, to look up
documentation, and so on. Where it differs most noticeably from
swankr is in the level of integration of various facilities with
emacs: ESS uses the browser() debugger, whereas swankr provides its
own debugger, sldb; swankr provides a custom REPL with hooks for
common commands; and so on. On the other hand, ESS is mature,
feature-rich software, while swankr is only a little more advanced
than a proof-of-concept. For Lisp programmers, perhaps the most
useful analogy is to say that swankr intends to be to ESS what
SLIME is to ILISP. At present, ESS mode remains active in R source
buffers, providing font-locking functionality among other things.
* Installation
** Running
To begin using swankr:
1. start R;
2. load the swank.R file:
#+BEGIN_SRC R
source("swank.R")
#+END_SRC
3. at the R prompt, run
#+BEGIN_SRC R
swank();
#+END_SRC
4. within emacs, load and initialize slime;
#+BEGIN_SRC emacs-lisp
(require 'slime)
(slime-setup '(slime-repl))
#+END_SRC
5. run =M-x slime-connect=, accepting the default host and port,
and acknowledging the protocol version mismatch.
At this point, an R REPL should appear.
** Emacs customization
At a minimum, slime needs to be set up to function. I've
used the following forms in my =~/.emacs=
#+BEGIN_SRC emacs-lisp
(require 'slime)
(slime-setup '(slime-repl slime-scratch slime-media))
#+END_SRC
The =slime-media= contrib is new and (at present) R-specific,
allowing for image results to be embedded in the REPL.
In addition, for keybindings like =C-c C-c= to work properly, emacs
needs to be told how to guess where a function definition begins.
This can be achieved with /e.g./
#+BEGIN_SRC emacs-lisp
(add-hook 'ess-mode-hook
(lambda ()
(setq defun-prompt-regexp "^\\(\\(\\sw\\|\\s_\\)+\\|\\s\"\\S\"+\\s\"\\)\\s-*\\(=\\|<-\\)\\s-*function\\s-*(.*)\\s-*")))
#+END_SRC
Fontification of quoted function names is suboptimal by default in
ESS; the following form in =~/.emacs= fixes that for ESS 5.11.
#+BEGIN_SRC emacs-lisp
(eval-after-load "ess-common"
(setq ess-R-mode-font-lock-keywords
(append
(list '("\\(\\sw\\|\\s_\\)+\\s-*\\(=\\|<-\\)\\s-*function"
1 font-lock-function-name-face t)
'("\\s\"\\(\\S\"+\\)\\s\"\\s-*\\(=\\|<-\\)\\s-*function"
1 font-lock-function-name-face t))
ess-R-mode-font-lock-keywords)))
#+END_SRC
* Development
swankr's primary development repository is a git repository,
accessible through
<http://common-lisp.net/r/users/crhodes/swankr.git> and
git://common-lisp.net/crhodes/swankr/swankr.git; a web view of the
development history is [[http://common-lisp.net/gitweb?p=users/crhodes/swankr.git][available through gitweb]]. You can also view
the current lists of [[file:BUGS.org]] and [[file:TODO.org]] items.
* Acknowledgments
Thanks to my colleagues at [[http://www.gold.ac.uk/][Goldsmiths, University of London]], for
suggesting that I investigate R for numerical and graphical
investigations, and to my colleagues at [[http://www.teclo.net/][Teclo Networks AG]] for giving
me motivation to get around to it. Initial development was done at
the [[http://ismir2010.ismir.net/][International Symposium on Music Information Retrieval]], which I
attended (indirectly) thanks to the EPSRC-funded [[http://www.omras2.org/][OMRAS2]] research
project and the [[http://www.londoninternational.ac.uk][University of London External System]]; Helmut Eller's
partial implementation of swank for Ruby was an excellent blueprint
to get development started.
* Footnotes
[fn:1] part of SLIME, the Superior Lisp Interaction Mode for Emacs:
<http://common-lisp.net/project/slime/>.
[fn:2] a free software environment for statistical computing and
graphics: <http://www.r-project.org/>.
[fn:3] also known as ESS, an emacs mode for interacting with a number
of statistical software packages, including R:
<http://ess.r-project.org/>.
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