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#+OPTIONS: H:3 num:nil toc:2 \n:nil @:t ::t |:t ^:{} -:t f:t *:t TeX:t LaTeX:t skip:nil d:(HIDE) tags:not-in-toc
#+STARTUP: align fold nodlcheck hidestars oddeven lognotestate hideblocks
#+SEQ_TODO: TODO(t) INPROGRESS(i) WAITING(w@) | DONE(d) CANCELED(c@)
#+TAGS: Write(w) Update(u) Fix(f) Check(c)
#+TITLE: Org-babel
#+AUTHOR: Eric Schulte, Dan Davison
#+EMAIL: schulte.eric at gmail dot com, davison at stats dot ox dot ac dot uk
#+LANGUAGE: en
#+CATEGORY: worg
# #+INFOJS_OPT: view:content
#+begin_html
<div id="subtitle">
<p>executable source code blocks in org-mode</p>
</div>
<div id="logo">
<p>
<img src="images/tower-of-babel.png" alt="images/tower-of-babel.png"/>
<div id="attr">
The Tower of Babel by
<a href="http://commons.wikimedia.org/wiki/Pieter_Brueghel_the_Elder" title="">
<b>Pieter Brueghel the Elder</b>
</a>
</div>
<p>
And the Lord said, Behold, the people is one, and they have all
one language; and this they begin to do; and now nothing will be
restrained from them, which they have imagined to do. Genesis
11:1-9
</p>
</p>
</div>
#+end_html
#+begin_html
<p>
</p>
#+end_html
* Introduction
:PROPERTIES:
:CUSTOM_ID: introduction
:END:
Org-babel is an extension to the very excellent [[http://orgmode.org/][Org-mode]], providing
the ability to execute source code in many different languages
within org-mode documents. The results of code execution --- text,
tables and graphics --- can be integrated into the powerful
publishing facilities of org-mode. Org-mode is an [[http://www.gnu.org/software/emacs/][Emacs]] major mode
for doing almost anything with plain text. If you are not familiar
with Org-mode please take a moment to read [[http://orgmode.org/][the Org-mode homepage]]
before continuing.
Org-babel provides the following modifications to [[http://orgmode.org/manual/Literal-examples.html][the existing
support]] for blocks of source code examples in the org-mode core.
1. Interactive source code execution
2. Arguments to source code blocks
3. Exportation of source code blocks to files (literate programming)
* Getting started
:PROPERTIES:
:CUSTOM_ID: getting-started
:END:
1) Grab the latest code from the git repo at [[http://github.com/eschulte/org-babel/tree/master][github/org-babel]]
#+begin_src sh
git clone git://github.com/eschulte/org-babel.git
#+end_src
2) Add the following lines to your .emacs, replacing the path as
appropriate. A good place to check that things are up and running
would the examples in [[* Basic org-babel functionality][Basic org-babel functionality]].
#+begin_src emacs-lisp
(add-to-list 'load-path "/path/to/org-babel/lisp")
(require 'org-babel-init)
#+end_src
3) Finally, activate the subset of supported Org-babel languages
which you want to be able to execute on your system. As an
example, the following activates python, ruby and R. For a full
list of languages, with notes on their dependencies see the
[[#reference-and-documentation][Reference / Documentation]] section below.
#+begin_src emacs-lisp
(require 'org-babel-python)
(require 'org-babel-ruby)
(require 'org-babel-R)
;;
;; Once you've activated languages, load the library of babel to
;; make pre-built helper functions available in the languages you will be using.
(org-babel-load-library-of-babel)
#+end_src
* Basic org-babel functionality
:PROPERTIES:
:CUSTOM_ID: basic-functionality
:END:
*** Source code blocks
:PROPERTIES:
:CUSTOM_ID: source-code-blocks
:END:
Org-babel is all about *source code blocks* in org mode. These are
blocks of code (in whatever language), that can occur anywhere in
an org-mode file. For example, the following is a source block
containing [[http://www.ruby-lang.org/][ruby]] code:
: #+begin_src ruby
: "This file was last evaluated on #{Date.today}"
: #+end_src
If you are unfamiliar with the notion of a source code block in
org-mode, please have a look at the [[http://orgmode.org/manual/Literal-examples.html][relevant manual section]] before
proceding.
Note that above is what the source block looks like in the org-mode
file. We had to take [[http://orgmode.org/manual/Literal-examples.html#Literal-examples][special steps]] to make it look that way in the
HTML output. Normally, when exported to HTML, source blocks are
fontified according to their language, and the begin_src...end_src
mark-up is omitted, like this:
#+begin_src ruby
"This file was last evaluated on #{Date.today}"
#+end_src
From now on, if you are viewing the HTML version, you will see the
HTML output only. However, much of this document consists of
interactive examples, and therefore in order to get a feeling for the
mechanics of Org-babel it might make most sense to grab the plain text
version of this file
#+HTML: <a href="org-babel-worg.org">org-babel-worg.org</a>
and work through it in Emacs. Alternatively the htmlized
version of the plain text of this file at
#+HTML: <a href="org-babel-worg.org.html">org-babel-worg.html</a>
allows the plain text version to be viewed (non-interactively) in a web browser.
*** Source code execution
:PROPERTIES:
:CUSTOM_ID: source-code-execution
:END:
For interpreted languages such as shell, python, R, etc, org-babel
allows source blocks to be executed: the code is passed to the
interpreter and you have control over what is done with the results of
execution. Here are three examples of code blocks in three different
languages, followed by their output. If you are viewing the plain text
version of this document in emacs, place point anywhere inside the
blocks and use =C-c C-c= to run the code[fn:1] (and feel free to alter
it!).
**** Ruby
#+begin_src ruby
"This file was last evaluated on #{Date.today}"
#+end_src
#+resname:
: This file was last evaluated on 2009-08-09
**** [[http://www.r-project.org/][R]]
#+begin_src R :results value
matrix(rnorm(6), nrow=2)
#+end_src
#+resname:
| -0.138279734486552 | -2.2476234005706 | -0.0839549402407832 |
| 0.0730510956002737 | 0.0634015508602321 | 0.174013159381603 |
**** [[http://ditaa.sourceforge.net/][ditaa]]
#+begin_src ditaa :file images/blue.png :cmdline -r
+---------+
| cBLU |
| |
| +----+
| |cPNK|
| | |
+----+----+
#+end_src
#+resname:
[[file:images/blue.png]]
*** Source code block syntax
The basic syntax of source-code blocks in Org-babel is as follows:
: #+srcname: name(arguments)
: #+begin_src language header-arguments
: body
: #+end_src
- name :: This name is associated with the source-code block. This is
similar to the =#+tblname= lines which can be used to name tables
in org-mode files. By referencing the srcname of a source-code
block it is possible to evaluate the block from other places,
files, or from inside tables.
- arguments :: Code blocks can have arguments (see [[#arguments-to-source-code-blocks][below]]) which are
provided using a familiar function-call syntax similar
to (e.g.) python or R.
- language :: The language of the code in the source-code block. Valid
values must be members of `org-babel-interpreters'.
- header-arguments :: Header arguments control many facets of the
evaluation and output of source-code blocks. See the [[* Header Arguments][Header
Arguments]] section for a complete review of available header
arguments.
- body :: The actual source code which will be evaluated. An
important key-binding to become familiar with is =C-c
'=. This calls `org-edit-special' which brings up an edit
buffer containing the code using the emacs major mode
appropriate to the language.
*** What happens to the results?
:PROPERTIES:
:CUSTOM_ID: results
:END:
Org-babel provides two fundamentally different modes for capturing
the results of code evaluation, specified by the =:results= header
argument.
**** =:results value= (functional mode)
This means that the 'result' of code evaluation is defined to be
the *value* of the last statement in the block. Thus with this
setting, one can view the code block as a function with a return
value. And not only can you view it that way, but you can
actually use the return value of one source block as input for
another (see [[meta-programming-language]]). This setting is the
default.
As an example, consider the following block of python code and its
output.
#+begin_src python :results value
import time
print("Hello, today's date is %s" % time.ctime())
print('Two plus two is')
2 + 2
#+end_src
#+resname:
: 4
Notice that in functional mode, the output consists of the value of
the last statement, and nothing else.
**** =:results output= (scripting mode)
With this setting, org-babel captures all the text output of the
code block and places it in the org buffer. One can think of this
as a 'scripting' mode: the code block contains a series of
commands, and you get the output of all the commands. Unlike in
the 'functional' mode, the code block has no return value. (This
mode will be more familiar to Sweave users).
Now consider the result of evaluating the same source block as
before, but under scripting mode.
#+srcname: name
#+begin_src python :results output
import time
print("Hello, today's date is %s" % time.ctime())
print('Two plus two is')
2 + 2
#+end_src
#+resname: name
: Hello, today's date is Fri Sep 4 19:49:06 2009
: Two plus two is
Again, we got what we asked for: all the text output (stdout) from
python. Since we didn't print the last value (2 + 2), we didn't get it
in our output.
*** Arguments to source code blocks
:PROPERTIES:
:CUSTOM_ID: arguments-to-source-code-blocks
:END:
In addition to evaluation of code blocks, org-babel allows them to
be parameterised (i.e. have arguments). Thus source code blocks
now have the status of *functions*. Arguments to code blocks can
be used in both functional and scripting mode.
**** Simple example of using a source block as a function
First let's look at a very simple example. The following source
block defines an org-babel function that will square its input.
#+srcname: square(x)
#+begin_src python
x*x
#+end_src
In the org-mode file that looks like this:
: #+srcname: square(x)
: #+begin_src python
: x*x
: #+end_src
Now we use the source block:
: #+lob: square(x=6)
(/for information on the/ =lob= /syntax see [[library-of-babel]]/)
#+lob: square(x=6)
#+resname: square(x=6)
: 36
**** A more complex example: using an org-table as input
In this example we're going to define a function to compute a
Fibonacci sequence, and we're going to make it take its input
from a table in the org-mode buffer.
Here are the inputs for fibonacci-seq:
#+tblname: fibonacci-inputs
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| 2 | 4 | 6 | 8 | 10 | 12 | 14 | 16 | 18 | 20 |
in the Org-mode buffer this looks like
: #+tblname: fibonacci-inputs
: | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
: | 2 | 4 | 6 | 8 | 10 | 12 | 14 | 16 | 18 | 20 |
[[http://www.gnu.org/software/emacs/manual/elisp.html][Emacs Lisp]] source code
#+srcname: fibonacci-seq(fib-inputs=fibonacci-inputs)
#+begin_src emacs-lisp
(defun fibonacci (n)
(if (or (= n 0) (= n 1))
n
(+ (fibonacci (- n 1)) (fibonacci (- n 2)))))
(mapcar (lambda (row)
(mapcar #'fibonacci row)) fib-inputs)
#+end_src
in the Org-mode buffer this looks like
: #+srcname: fibonacci-seq(fib-inputs=fibonacci-inputs)
: #+begin_src emacs-lisp
: (defun fibonacci (n)
: (if (or (= n 0) (= n 1))
: n
: (+ (fibonacci (- n 1)) (fibonacci (- n 2)))))
:
: (mapcar (lambda (row)
: (mapcar #'fibonacci row)) fib-inputs)
: #+end_src
Results of Emacs Lisp code evaluation
#+resname:
| 1 | 1 | 2 | 3 | 5 | 8 | 13 | 21 | 34 | 55 |
| 1 | 3 | 8 | 21 | 55 | 144 | 377 | 987 | 2584 | 6765 |
* A meta-programming language for org-mode
:PROPERTIES:
:CUSTOM_ID: meta-programming-language
:END:
Since information can pass freely between source-code blocks and
org-mode tables you can mix and match languages using each language
for those tasks to which it is suited. This makes Org-mode files with
Org-babel into a kind of meta-functional programming language in which
functions from many languages can work together.
As an example, lets take some system diagnostics in the shell, and
then graph them with R.
1. First we create a code block containing shell code creating a list
of the directories in our home directory, together with their
sizes. Org-babel automatically converts the output into an org
table.
#+srcname: directories
#+begin_src bash :results replace
cd ~ && du -sc * |grep -v total
#+end_src
#+resname: directories
| 72 | "Desktop" |
| 12156104 | "Documents" |
| 3482440 | "Downloads" |
| 2901720 | "Library" |
| 57344 | "Movies" |
| 16548024 | "Music" |
| 120 | "News" |
| 7649472 | "Pictures" |
| 0 | "Public" |
| 152224 | "Sites" |
| 8 | "System" |
| 56 | "bin" |
| 3821872 | "mail" |
| 10605392 | "src" |
| 1264 | "tools" |
2. Now we use a single line of R code to plot the data as a
pie-chart. Note the way that this source block uses the =srcname=
of the previous source block to obtain the data.
#+srcname: directory-pie-chart(dirs = directories)
#+begin_src R :session R-pie-example
pie(dirs[,1], labels = dirs[,2])
#+end_src
[[file:images/dirs.png]]
* Multilingual spreadsheet plugins for org-mode
:PROPERTIES:
:CUSTOM_ID: spreadsheet
:END:
*NOTE*: Maybe in-addition-to/in-stead-of this example we should do a
more traditional "spreadsheet" example with R [Eric]
Not only can Org-babel pass entire tables of data to source code
blocks (see [[arguments-to-source-code-blocks]]), Org-babel can also be
used to call source code blocks from *within* tables using the
Org-mode's [[http://orgmode.org/manual/The-spreadsheet.html#The-spreadsheet][existing spreadsheet functionality]].
In fact the functional test suite for Org-babel is implemented as a
large Org-mode table. To run the entire test suite you simple
evaluate the table =C-u C-c C-c=, and all of the tests are run
updating the table with pass/fail statistics.
Here's a sample of our test suite.
#+TBLNAME: org-babel-tests
| functionality | block | arg | expected | results | pass |
|------------------+--------------+-----+-------------+-------------+------|
| basic evaluation | | | | | pass |
|------------------+--------------+-----+-------------+-------------+------|
| emacs lisp | basic-elisp | 2 | 4 | 4 | pass |
| shell | basic-shell | | 6 | 6 | pass |
| ruby | basic-ruby | | org-babel | org-babel | pass |
| python | basic-python | | hello world | hello world | pass |
| R | basic-R | | 13 | 13 | pass |
#+TBLFM: $5='(if (= (length $3) 1) (progn (message (format "running %S" '(sbe $2 (n $3)))) (sbe $2 (n $3))) (sbe $2))::$6='(if (string= $4 $5) "pass" (format "expected %S but was %S" $4 $5))
#+TBLFM: $5=""::$6=""
*** code blocks for tests
#+srcname: basic-elisp(n=7)
#+begin_src emacs-lisp
(* 2 n)
#+end_src
#+srcname: basic-shell
#+begin_src sh :results silent
expr 1 + 5
#+end_src
#+srcname: date-simple
#+begin_src sh :results silent
date
#+end_src
#+srcname: basic-ruby
#+begin_src ruby :results silent
"org-babel"
#+end_src
#+srcname: basic-python
#+begin_src python :results silent
'hello world'
#+end_src
#+srcname: basic-R
#+begin_src R :results silent
b <- 9
b + 4
#+end_src
* The Library of Babel
:PROPERTIES:
:CUSTOM_ID: library-of-babel
:END:
#+begin_html
<div id="logo">
<p>
<img src="images/library-of-babel-clayette.png" />
<div id="attr">
The Library of Babel, by Pierre Clayette
<p>
<a href="http://downlode.org/Etext/library_of_babel.html">Full text of the Borges short story</a>
</p>
</div>
</p>
</div>
#+end_html
As we saw above with the [[*Simple%20example%20of%20using%20a%20source%20block%20as%20a%20function][=square=]] example, once a source block
function has been defined it can be called using the following short =lob= notation:
: #+lob: square(x=6)
But what about those source code blocks which are so useful you want
to have them available in every org-mode buffer?
In addition to the current buffer, Org-babel searches for
pre-defined source block functions in the Library of Babel. This is
a user-extensible collection of ready-made source-code blocks for
handling common tasks. One use for the LoB (not yet done!) will be
to provide a choice of data graphing procedures for data held in
org-mode tables, using languages such as R, gnuplot, asymptote,
etc. If you implement something that might be of use to other org
users, please consider adding it to the LoB; similarly, feel free to
request help solving a problem using external code via org-babel --
there's always a chance that other org users will be able to
contribute some helpful code. Org-mode demonstrates that an enormous
amount can be achieved using plain text and emacs lisp; the LoB is
intended to fill in the gaps.
Org-babel comes pre-populated with the source-code blocks located in
the [[file:library-of-babel.org][library-of-babel.org]] file. It is possible to add source-code
blocks from any org-mode file to the library by calling
#+srcname: add-file-to-lob
#+begin_src emacs-lisp
(org-babel-lob-ingest "path/to/file.org")
#+end_src
Note that it is also possible to pass table values or the output of
a source-code block to lob functions, and it is possible to
reference lob functions in source block arguments.
* Reproducible Research
:PROPERTIES:
:CUSTOM_ID: reproducable-research
:END:
#+begin_quote
An article about computational science in a scientific publication is
not the scholarship itself, it is merely advertising of the
scholarship. The actual scholarship is the complete software
development environment and the complete set of instructions which
generated the figures.
-- D. Donoho
#+end_quote
[[http://reproducibleresearch.net/index.php/Main_Page][Reproducible Research]] (RR) is the practice of distributing along with
an article of research all data, code, and tools required to reproduce
the results discussed in the paper. As such the paper becomes not
only a document describing the research but a complete laboratory in
which the research can be reproduced and extended.
Org-mode already has exceptional support for [[http://orgmode.org/manual/Exporting.html#Exporting][exporting to html and
LaTeX]]. Org-babel makes Org-mode a tool for RR by *activating* the
data and source code embedded into Org-mode documents making the
entire document executable. This makes it not only possible, but
natural to distribute research in a format that encourages readers to
recreate your results, and perform their own analysis.
One notable existing RR tool is [[http://en.wikipedia.org/wiki/Sweave][Sweave]] which provides for the
embedding of [[http://www.r-project.org/][R]] code into LaTeX documents. While Sweave is a mature
and very useful tool, we believe that Org-babel has several
advantages:
- It supports multiple languages (we're not aware of other RR tools that do this)
- The [[http://orgmode.org/manual/Exporting.html#Exporting][export process]] is flexible and powerful, including HTML as a target in addition to LaTeX
- The document can make native use of all the features of Org-mode,
such as those for [[http://orgmode.org/manual/Agenda-Views.html#Agenda-Views][project planning]] and [[http://orgmode.org/manual/TODO-Items.html#TODO-Items][task management]]
* Literate programming
:PROPERTIES:
:CUSTOM_ID: literate-programming
:END:
#+begin_quote
Let us change our traditional attitude to the construction of
programs: Instead of imagining that our main task is to instruct a
/computer/ what to do, let us concentrate rather on explaining to
/human beings/ what we want a computer to do.
The practitioner of literate programming can be regarded as an
essayist, whose main concern is with exposition and excellence of
style. Such an author, with thesaurus in hand, chooses the names of
variables carefully and explains what each variable means. He or she
strives for a program that is comprehensible because its concepts have
been introduced in an order that is best for human understanding,
using a mixture of formal and informal methods that reinforce each
other.
-- Donald Knuth
#+end_quote
Org-babel supports [[http://en.wikipedia.org/wiki/Literate_programming][Literate Programming]] (LP) by allowing the act of
programming to take place inside of Org-mode documents. The Org-mode
file can then be exported (*woven* in LP speak) to html or LaTeX for
consumption by a human, and the embedded source code can be extracted
(*tangled* in LP speak) into structured source code files for
consumption by a computer.
To support these operations Org-babel relies on Org-mode's [[http://orgmode.org/manual/Exporting.html#Exporting][existing
exporting functionality]] for *weaving* of documentation, and on the
=org-babel-tangle= function which makes use of [[http://www.cs.tufts.edu/~nr/noweb/][Noweb]] [[reference-expansion][reference syntax]]
for *tangling* of code files.
The [[literate-programming-example][following example]] demonstrates the process of *tangling* in
Org-babel.
*** Simple Literate Programming Example (Noweb syntax)
:PROPERTIES:
:CUSTOM_ID: literate-programming-example
:END:
Tangling functionality is controlled by the =tangle= family of
[[header-arguments]]. These arguments can be used to turn tangling on or
off (the default) on the source code block, or the outline heading
level.
The following demonstrates the combination of three source code blocks
into a single source code file using =org-babel-tangle=.
The following two blocks will not be tangled by default since they
have no =tangle= header arguments.
#+srcname: hello-world-prefix
#+begin_src sh :exports none
echo "/-----------------------------------------------------------\\"
#+end_src
: #+srcname: hello-world-prefix
: #+begin_src sh :exports none
: echo "/-----------------------------------------------------------\\"
: #+end_src
#+srcname: hello-world-postfix
#+begin_src sh :exports none
echo "\-----------------------------------------------------------/"
#+end_src
: #+srcname: hello-world-postfix
: #+begin_src sh :exports none
: echo "\-----------------------------------------------------------/"
: #+end_src
The third block does have a =tangle= header argument indicating the
name of the file to which it should be written. It also has [[http://www.cs.tufts.edu/~nr/noweb/][Noweb]]
style references to the two previous source code blocks which will be
expanded during tangling to include them in the output file as well.
#+srcname: hello-world
#+begin_src sh :tangle hello :exports none
# <<hello-world-prefix>>
echo "| hello world |"
# <<hello-world-postfix>>
#+end_src
: #+srcname: hello-world
: #+begin_src sh :tangle hello :exports none
: # <<hello-world-prefix>>
: echo "| hello world |"
: # <<hello-world-postfix>>
: #+end_src
Calling =org-babel-tangle= will result in the following being written
to the =hello.sh= file.
#+srcname: hello-world-output
#+begin_src sh
#!/usr/bin/env sh
# generated by org-babel-tangle
# [[file:~/src/org-babel/org-babel-worg.org::#literate-programming-example][block-16]]
# <<hello-world-prefix>>
echo "/-----------------------------------------------------------\\"
echo "| hello world |"
# <<hello-world-postfix>>
echo "\-----------------------------------------------------------/"
# block-16 ends here
#+end_src
*** Emacs Initialization with Org-babel
Org-babel has special support for embedding your emacs initialization
into Org-mode files. The =org-babel-load-file= function can be used
to load the emacs lisp embedded in a literate Org-mode file in the
same way that you might load a regular elisp file.
This allows you to have all the niceness of Org-mode (folding, tags,
notes, html export, etc...) available in your emacs initialization.
To try this out either see the simple [[literate-emacs-init][Literate Emacs Initialization]]
example directly below, or check out the Org-babel Literate
Programming version of Phil Hagelberg's excellent [[http://github.com/technomancy/emacs-starter-kit/tree/master][emacs-starter-kit]]
available at [[http://github.com/eschulte/emacs-starter-kit/tree/master][Org-babel-emacs-starter-kit]].
***** Literate Emacs Initialization
:PROPERTIES:
:CUSTOM_ID: literate-emacs-init
:END:
For a simple example of usage follow these 4 steps.
1) create a directory named =.emacs.d= in the base of your home
directory.
#+begin_src sh
mkdir ~/.emacs.d
#+end_src
2) checkout the latest versions of Org-mode and Org-babel into the src
subdirectory of this new directory
#+begin_src sh
cd ~/.emacs.d
mkdir src
cd src
git clone git://repo.or.cz/org-mode.git
git clone git://github.com/eschulte/org-babel.git
#+end_src
3) place the following in a file called =init.el= in your emacs
initialization directory (=~/.emacs.d=).
#+srcname: emacs-init
#+begin_src emacs-lisp
;;; init.el --- Where all the magic begins
;;
;; This file loads both
;; - Org-mode : http://orgmode.org/ and
;; - Org-babel: http://eschulte.github.com/org-babel/
;;
;; It then loads the rest of our Emacs initialization from Emacs lisp
;; embedded in literate Org-mode files.
;; Load up Org Mode and Org Babel for elisp embedded in Org Mode files
(setq dotfiles-dir (file-name-directory (or (buffer-file-name) load-file-name)))
(add-to-list 'load-path (expand-file-name
"lisp" (expand-file-name
"org" (expand-file-name
"src" dotfiles-dir))))
(add-to-list 'load-path (expand-file-name
"lisp" (expand-file-name
"org-babel" (expand-file-name
"src" dotfiles-dir))))
(require 'org-babel-init)
;; load up all literate org-mode files in this directory
(mapc #'org-babel-load-file (directory-files dotfiles-dir t "\\.org$"))
;;; init.el ends here
#+end_src
4) Implement all of your emacs customizations inside of elisp
source-code blocks located in Org-mode files in this directory.
They will be loaded by emacs on startup.
* Reference / Documentation
:PROPERTIES:
:CUSTOM_ID: reference-and-documentation
:END:
*** Languages
The following can be added to your .emacs and used to activate
languages. It includes a brief list of the requirements for each
language. *Note*: this also serves as the list of languages
currently supported by Org-babel.
#+begin_src emacs-lisp
;; Uncomment each of the following require lines if you want org-babel
;; to support that language. Each language has a comment explaining
;; it's dependencies. See the related files in lisp/langs for more
;; detailed explanations of requirements.
;; (require 'org-babel-R) ;; R and ess-mode
;; (require 'org-babel-asymptote) ;; asymptote
;; (require 'org-babel-css) ;; none
;; (require 'org-babel-ditaa) ;; ditaa
;; (require 'org-babel-dot) ;; dot
;; (require 'org-babel-gnuplot) ;; gnuplot, and gnuplot-mode
;; (require 'org-babel-haskell) ;; haskell, haskell-mode, inf-haskell
;; (require 'org-babel-ocaml) ;; ocaml, and tuareg-mode
;; (require 'org-babel-python) ;; python, and python-mode
;; (require 'org-babel-ruby) ;; ruby, irb, ruby-mode, and inf-ruby
;; (require 'org-babel-sass) ;; sass, sass-mode
;; (require 'org-babel-sql) ;; none
#+end_src
*** Header Arguments
:PROPERTIES:
:CUSTOM_ID: header-arguments
:END:
- results :: results arguments specify what should be done with the
output of source-code blocks
- The following options are mutually exclusive, and specify how the
results should be collected from the source-code block
- value ::
- output ::
- The following options are mutually exclusive and specify what type
of results the code block will return
- vector :: specifies that the results should be interpreted as a
multidimensional vector (even if the vector is
trivial), and will be inserted into the org-mode file
as a table
- scalar :: specifies that the results should be interpreted as a
scalar value, and will be inserted into the org-mode
file as quoted text
- file :: specifies that the results should be interpreted as the
path to a file, and will be inserted into the org-mode
file as a link
- The following options specify how the results should be inserted
into the org-mode file
- replace :: the current results replace any previously inserted
results from the code block
- silent :: rather than being inserted into the org-mode file the
results are echoed into the message bar
- exports :: exports arguments specify what should be included in html
or latex exports of the org-mode file
- code :: the body of code is included into the exported file
- results :: the results of evaluating the code is included in the
exported file
- both :: both the code and results are included in the exported
file
- none :: nothing is included in the exported file
- tangle :: tangle arguments specify whether or not the source-code
block should be included in tangled extraction of
source-code files
- yes :: the source-code block is exported to a source-code file
named after the basename (name w/o extension) of the
org-mode file
- no :: (default) the source-code block is not exported to a
source-code file
- other :: any other string passed to the =tangle= header argument
is interpreted as a file basename to which the block will
be exported
*** Noweb reference syntax
The [[http://www.cs.tufts.edu/~nr/noweb/][Noweb]] Literate Programming system allows named blocks of code to
be referenced by using a =<<code-block-name>>= syntax. When a
document is tangled these references are replaced with the named code.
An example is provided in the [[literate-programming-example]] in this
document.
* Footnotes
[fn:1] Calling =C-c C-o= on a source-code block will open the
block's results in a separate buffer.
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