swankr: SWANK (and SLIME) for R

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

Emacs configuration

Installing SLIME

SLIME is required separately from swankr. To install slime, perhaps the simplest is to pull the git sources into a user-specific site directory, and arrange for that to be on the emacs load-path; something like the following:

mkdir -p ~/.emacs.d/site-lisp
cd ~/.emacs.d/site-lisp
git clone https://github.com/slime/slime.git

Following that, I have in my ~/.emacs (you will need to adjust paths to executables and source files):

;;; ~/.emacs.d/
(let ((default-directory (concat user-emacs-directory (convert-standard-filename "site-lisp/"))))
  (normal-top-level-add-subdirs-to-load-path))

;;; SLIME
(require 'slime)
(setq slime-net-coding-system 'utf-8-unix)
(slime-setup '(slime-asdf slime-repl slime-scratch slime-presentations slime-media))
(setq slime-lisp-implementations
      '((sbcl ("sbcl" "--dynamic-space-size" "2048" "--load" "/home/csr21/src/lisp/quicklisp/setup.lisp"))
        (git-sbcl ("sh" "/home/csr21/src/lisp/sbcl/run-sbcl.sh" "--dynamic-space-size" "2048"))
        (R ("R" "--no-save" "--max-vsize=4096M" "--interactive")
           :init (lambda (port-filename coding-system) 
                   (load "/home/csr21/src/R/swankr/swankr")
                   (format
                    "source('/home/csr21/src/R/swankr/swank.R', keep.source=TRUE, chdir=TRUE)\nstartSwank('%s')\n" port-filename)))))
(global-set-key (kbd "s-s") 'slime-selector)

Additional refinements

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.

(add-hook 'ess-mode-hook
  (lambda () 
    (setq defun-prompt-regexp "^\\(\\(\\sw\\|\\s_\\)+\\|\\s\"\\S\"+\\s\"\\)\\s-*\\(=\\|<-\\)\\s-*function\\s-*(.*)\\s-*")))

Fontification of quoted function names is suboptimal by default in ESS; the following form in ~/.emacs fixes that for ESS 5.11.

(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)))

Running

After performing the installation steps above, M-- M-x slime RET R RET should start swank. You will be prompted to accept a version mismatch – simply accept – then the SLIME REPL should start up, giving a prompt. Enjoy!

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/users/crhodes/swankr.git; a web view of the development history is available through gitweb. You can also view the current lists of BUGS.org and TODO.org items.

Acknowledgments

Thanks to my colleagues at Goldsmiths, University of London, for suggesting that I investigate R for numerical and graphical investigations, and to my colleagues at Teclo Networks AG for giving me motivation to get around to it. Initial development was done at the International Symposium on Music Information Retrieval, which I attended (indirectly) thanks to the EPSRC-funded OMRAS2 research project and the 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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