Version 0.7, March 04, 2017

Albert Graef <aggraef@gmail.com>

pure-doc is a simple utility for literate programming and documenting source code written in the Pure programming language. It is designed to be used with the excellent docutils tools and the gentle markup format supported by these, called RST a.k.a. “reStructuredText”, usually pronounced “rest”.

The basic idea is that you just comment your code as usual, but using RST markup instead of plain text. In addition, you can also designate literate programming fragments in your code, which will be translated to RST literal blocks automatically. You then run pure-doc on your source files to extract all marked up comments and the literate code blocks. The resulting RST source can then be processed with the docutils utilities like rst2html.py and rst2latex.py to create the documentation in a variety of formats.


Copyright (c) 2009-2010 by Albert Graef.

pure-doc is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

pure-doc is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>.


Get the latest source from https://bitbucket.org/purelang/pure-lang/downloads/pure-doc-0.7.tar.gz.

Unpack and do the customary make && sudo make install. This only needs flex and a standards-compliant C++ compiler.


First, see the description of the RST format. RST is a very simple markup format, almost like plain text (in fact, you’re looking at RST right now, this document is written in it!). You can learn enough of it to start marking up your source in about five minutes.

Second, you’ll have to mark up your source comments. pure-doc recognizes comments in RST format by looking at the first non-empty line of the comment. A comment (either /* ... */ or a contiguous sequence of // line comments) is assumed to contain RST format if the first non-empty line starts with :, .. or __. Other comments are taken to be plain text and are ignored by pure-doc.


  • pure-doc makes no other assumption about the contents of marked up comments, so you can include whatever you want: titles, section headers, fields, admonitions, plain text, whatever. Just make sure that the comment starts with one of the special tokens listed above. (You can always put just .. at the beginning of the comment to force it to be recognized, this will be treated as a comment by the docutils tools.)
  • Also, pure-doc makes very few assumptions about the source; in fact, any source files with a C/C++-like comment and string syntax should work. So you could also use it to document your C/C++ programs, or even plain text files like this one, as long as they adhere to these standards.
  • Indentation in extracted comments is preserved (assuming tabs = 8 spaces by default, you can change this with the -t option). This is important because indentation conveys document structure in RST.

For instance, here is a sample RST-formatted comment:

/* :Name: ``rand`` - compute random numbers
   :Synopsis: ``rand``
   :Description: Computes a (pseudo) random number. Takes no parameters.
   :Example: Here is how you can call ``rand`` in Pure:

       > extern int rand();
       > rand;

   :See Also: rand(3) */

This will be rendered as follows:


rand - compute random numbers




Computes a (pseudo) random number. Takes no parameters.


Here is how you can call rand in Pure:

> extern int rand();
> rand;
See Also:


Finally, to extract the documentation you run pure-doc on your source files as follows:

pure-doc source-files ...

If no input files are specfied then the source is read from standard input. Otherwise all input files are read and processed in the indicated order. The output is written to stdout, so that you can directly pipe it into one of the docutils programs:

pure-doc source-files ... | rst2html.py

If you prefer to write the output to a file, you can do that as follows:

pure-doc source-files ... > rst-file

pure-doc also understands the following options. These must come before any file arguments.

-h Print a short help message.
-i Automatic index creation (see below).
-s Generate Sphinx-compatible output (see below).
-twidth Set the tab width to the given number of spaces.

There are no other options. By its design pure-doc is just a plain simple “docstring scraping” utility with no formatting knowledge of its own. All actual formatting is handled by the docutils programs which offer plenty of options to change the appearance of the generated output; please refer to the docutils documentation for details.

Note that since Pure 0.46, all Pure documentation is usually formatted using Sphinx, the RST formatter used by the Python project which provides cross-document indexing and referencing, and even more elaborate formatting options and prettier output than docutils. pure-doc versions since 0.6 support this by adding the -s option which makes its output compatible with Sphinx. (At present this option actually has any effect only when combined with the -i index generation option, see Hyperlink Targets and Index Generation below.)

Literate Programming

pure-doc also recognizes literate code delimited by comments which, besides the comment delimiters and whitespace, contain nothing but the special start and end “tags” >>> and <<<. Code between these delimiters (including all comments) is extracted from the source and output as a RST literal code block.

For instance:

/* ..

   pure-doc supports literate programming, too. */

// >>>

// This is a literate comment.
/* .. This too! */

extern int rand();

// <<<

This will be rendered as follows:

pure-doc supports literate programming, too.

// This is a literate comment.
/* .. This too! */

extern int rand();

Try it now! You can scrape all the sample “documentation” from this file and format it as html, as follows:

pure-doc README | rst2html.py --no-doc-title --no-doc-info > test.html

Generating and Installing Local Documentation


This section only applies to 3rd party packages with their own bundled documentation which isn’t part of the “official” Pure documentation. In this case it is possible to use docutils or some other RST formatting software to generate additional documentation files for use with the Pure interpreter. Please note that the method sketched out in this section doesn’t provide full integration with the rest of Pure’s documentation, but at least it makes it possible to read the local documentation in the interpreter.

If you’re generating some library documentation for which you have to process a bigger collection of source files, then it is often convenient to have a few Makefile rules to automatize the process. To these ends, simply add rules similar to the following to your Makefile (the following assumes GNU make and that you’re using docutils to format the documentation):

# The sources. Order matters here. The generated documentation will have the
# comments from each source file in the indicated order.
sources = foo.pure bar.pure

# The basename of the documentation files to be generated.
target = foo

.PHONY: html tex pdf

html: $(target).html
tex: $(target).tex
pdf: $(target).pdf

$(target).txt: $(sources)
        pure-doc $(sources) > $@

# This requires that you have docutils installed.

%.html: %.txt
        rst2html.py $< $@

%.tex: %.txt
        rst2latex.py $< $@

# This also requires that you have TeX installed.

%.pdf: %.tex
        pdflatex $<
        rm -f *.aux *.log *.out

        rm -f *.html *.tex *.pdf

You might want to add -i to the pure-doc command line if you want to enable the indexing feature described in the previous section. If you want to use some other RST formatting software, please check the corresponding documentation for information on how to format your documents and adjust the above rules for the html, tex and pdf targets accordingly.

Now you can just type make html to generate the documentation in html format, and make tex or make pdf to generate the other formats. The clean target removes the generated files.

Having generated the documentation files in html format, you can install them in the docs subdirectory of the Pure library directory to make it known to the Pure interpreter, so that you can read your documentation with the help command of the interpreter. (When doing this, name your documentation files in such a manner that you don’t overwrite any of the Pure documentation files there.) The following Makefile rule automatizes this process. Add this to the Makefile in the previous section:

# Try to guess the installation prefix (this needs GNU make):
prefix = $(patsubst %/bin/pure,%,$(shell which pure 2>/dev/null))
ifeq ($(strip $(prefix)),)
# Fall back to /usr/local.
prefix = /usr/local

libdir = $(prefix)/lib
docsdir = $(libdir)/pure/docs

        test -d "$(DESTDIR)$(docsdir)" || mkdir -p "$(DESTDIR)$(docsdir)"
        cp $(target).html "$(DESTDIR)$(docsdir)"

After a make install your documentation should now end up in the appropriate place in the Pure library directory and you can read it in the Pure interpreter using a command like the following:

> help foo#

Note the hash character. This tells the help command that this is an auxiliary documentation file, rather than a search term to be looked up in the Pure documentation. You can also look up a specific section in your manual as follows:

> help foo#section-name

Please also refer to The Pure Manual for more information on how to use the interpreter’s online help.

Formatting Tips

If you’re generating documentation in pdf format using plain docutils, you might have to fiddle with the formatting to get results suitable for publication purposes. Newer versions of the rts2latex.py program provide some options which let you adjust the formatting of various document elements. Here are the options that the author found particularly helpful:

  • The table of contents that RST produces isn’t all that useful in printed documentation, since it lacks page numbers. As a remedy, you can invoke rst2latex with --use-latex-toc to have LaTeX handle the formatting of the table of contents, which looks much nicer.
  • Similarly, --use-latex-docinfo can be used to tell rst2latex that you want the title information (author and date) to be formatted the LaTeX way.
  • If you need specific LaTeX document options, these can be specified with --documentoptions, e.g.: --documentoptions="11pt".
  • For more comprehensive formatting changes which require special LaTeX code and/or packages, you can use the --stylesheet option. E.g., --stylesheet=preamble.tex will cause a preamble.tex file with your own definitions to be included in the preamble of the generated document.
  • To format literal code blocks using an alternative environment instead of the default verbatim environment, use the --literal-block-env option. E.g., --literal-block-env=lstlisting will use the highlighted code environment from the listings package. (Note that in this case you’ll also need a preamble which loads the corresponding package.).

To learn more about this, please consult the rts2latex.py documentation at the docutils website.

In addition, the pure-doc package contains a little GNU awk script called fixdoc, which attempts to improve the LaTeX output produced by older svn versions of rst2latex in various ways. (This isn’t necessary for the latest rst2latex versions, or if you use Sphinx.)