For a course in computational group theory I have to write a report about an implementation in GAP, and this is absolutely impossible without the best possible syntax highlighting, right? So I have entertained myself with implementing a GAP lexer. Its implementation is available at github.com/pbelmans/gap-pygments-lexer.

I have supplied an automatic installer, as the README suggests it boils down to

1. git clone git://github.com/pbelmans/gap-pygments-lexer.git or download and extract the archive GitHub automatically creates at the project’s Downloads page
2. cd gap-pygments-lexer
3. sudo python setup.py install

I would like to thank Wim Thys for providing me with the names of all the built-in classes and functions, using a bit of sed magic.

If you feel inspired, there are several other languages that need an implementation:

• Maple
• Magma (but they are be working on it themselves apparently)
• PARI/GP (this one has the most intriguing syntax of all)

So in text mode you write \v{C}ech, and in case you wish to write down the -th Čech cohomology group of a topological space and the sheaf you use \check{\mathrm{H}}^n(X,\mathcal{F}). Notice the use of \mathrm{H} for the actual (co)homology object, you could/should do this too!

Don’t shoot the nitpicky typesetting aficionado please. And consider using a macro like \newcommand\HH{\mathrm{H}} for easier typing. And of course \newcommand\cHH{\check{\mathrm{H}}}.

Let this fact be known too.

So I have decided to implement a UGent beamer theme myself, adhering to the style guide and following the philosophy set out by Nico. The implementation is available at GitHub, by means of the ugent-beamer project. I have rewritten Nico’s documentation to match my personal view on the subject of beamer themes, the result is available as a separate download. In case you wish to use the theme and you’re not that git-savvy, you can download the archive at the Downloads page. It contains all the necessary files, including the documentation.

The first two slides from the example I have supplied are

Installing beamer themes can be quite a hassle if you’re not acquainted with the inner workings of MiKTeX or TeX Live, but it should be thoroughly explained in the documentation. If anything is not clear or something is wrong, please let me know. As for now, there are still several things I would like to do with the theme in the future, they are listed at the Issues page.

\makeatletter
\newcommand\href@footnote[2]{#2\footnote{\url{#1}}}
\DeclareRobustCommand{\href}{\hyper@normalise\href@footnote}
\makeatother

I’m not claiming any originality here, but you might find it useful.

Anyhow, in case you want to use my material (conceived as 4 weeks of 3 hours classes each), please contact me, but otherwise you’re free to use them for your own benefit. The actual material is available at the ACM Antwerp LaTeX course page (not complete yet), the code necessary to create it is available at github.com/pbelmans/Dutch-LaTeX-course (where else…), using pdflatex --shell-escape slides and building several times should do the trick if you’ve got Pygments with correct Pygments style and the correct beamer theme installed.

I realize this post has little or no value if you don’t speak Dutch, my apologies if this applies to you.

You know variable-sized delimiters: they are either the \left(, \right) combo or variations on \big) making all your delimiters look good in LaTeX. But \uparrow and its related arrows \downarrow, \Downarrow, \Uparrow, \updownarrow and \Updownarrow are variable-sized delimiters too! Which means they can be used to spice up your commutative diagram a little.

Compare

to
.

The difference isn’t shocking but it does like a little nicer. Another useful tricks when typesetting commutative diagrams in an array environment: use \phantom to center your labels next to a vertical arrow. In case you’re wondering what the complete code for this example looks like:

\begin{array}{ccccc}
  & & \mathrm{Nr}(\mathbb{Z}) & & \\
  & & \phantom{\textrm{itp}}\Big\downarrow\textrm{itp} & & \\
  \mathrm{W}(\mathbb{Z}) & \overset{\tau}{\longrightarrow} & \hat{\Omega}(\mathrm{C}_\infty) & \overset{\mathrm{s}_t}{\longrightarrow} & \Lambda(\mathbb{Z}) \\
  \phantom{\Phi}\Big\downarrow\Phi & & \phantom{\hat{\varphi}}\Big\downarrow\hat{\varphi} & & \phantom{\mathrm{L}_{\mathbb{Z}}}\Big\downarrow\mathrm{L}_{\mathbb{Z}} \\
  \prod_{n=1}^{+\infty}\mathbb{Z} & \longleftrightarrow & \mathrm{gh}(\mathrm{C}_\infty)=\mathbb{Z}^{\mathbb{N}^\times} & \longleftrightarrow & t\mathbb{Z}[\![t]\!]
\end{array}

And in case you’re wondering about what the diagram actually means: it is the key diagram in explaining the relations between structures related to the ring of big Witt vectors and is taking from the paper The Burnside ring of the infinite cyclic group and its relations to the necklace algebra, -rings, and the universal ring of Witt vectors.

I have found out about XyJax, which allows you to use xypic code in MathJax, but I wasn’t aware at the time of writing the diagram and it’s still an alpha release. Yet, it looks promising and complete obsoletes the reason for this post!

• spelling mistakes
• inconsistencies
• there are still English words in the translated text
• incomplete translations (although the parts that were missing won’t show up in your every day scenario, it’s rather nit-picky)
• boring implementation of ordinal numbers (1e and 19e instead of 1ste and 19de)

As I’ve done before in A correct implementation of the Dutch language in babelbib, I have updated the necessary files. And in my current GitHub mania, I have uploaded this little project to github.com/pbelmans/dutch.lbx.

I have filed a contribution request at biblatex‘s SourceForge project page (GitHub is definitely superior SourceForge by the way) hoping it will be accepted in version 1.7 of biblatex, but in the meanwhile you can use this fix directly if you want. Just place dutch.lbx in $TEXMFHOME/tex/latex/biblatex/lbx/ creating the directories as you go (as discussed in Adding ~/.texmf to TeX Live 2011′s directories, or installing beamer themes). It should automatically supersede the dutch.lbx that’s present in $TEXMF/tex/latex/biblatex/lbx.

Of course, any contributions or remarks are always welcome, but I suspect the majority of my readers don’t speak Dutch.

After a bit of fiddling with memoir.dtx (any .dtx file is the documented source of a LaTeX package or class) I hacked together the desired result. A bit of \makeatletter magic and calling the correct macros did what I wanted.

For future reference, here it is.

If you want to change the marker using \thanksmarkseries{...}, start your titlingpage environment with the following:

\thanksmarkseries{alph}
\makeatletter
\@bsmarkseries
\makeatother

The main part of the solution simply is to mention

\makeatletter
\usethanksrule
\@thanks
\makeatother

at the end of the titlingpage environment. Note that \usethanksrule is not necessary but it feels better to have it.

There is the undocumented \saythanks macro though, but it is buggy: it always uses fnsymbol as its marker for the actual footnote. Behaviour that could be fixed I presume.

What is “installing a package” by the way? It boils down to letting programs like pdflatex know where certain files are situated. Installing is therefore nothing but dumping the necessary files somewhere and let TeX know where it can find them. But TeX doesn’t look everywhere, so we have to choose a place to dump the files and tell TeX they’re there.

As Manuel Pégourié-Gonnard pointed out in the comments, this extensive approach isn’t quite necessary. If you want to add your own files to ~/texmf, just perform Step 7 (after creating the folder as in Step 1, of course). This should do the trick, without further ado.

In case you want the “hidden folder approach” I wrote about, performing Steps 1, 2, the first line of Step 4 and Step 7 should be fine.

A quick yet extensively documented howto:

1. Open a shell and create your (hidden) local texmf folder by invoking mkdir ~/.texmf.
2. Locate texmf.cnf by invoking kpsewhich texmf.cnf. You should end up with a path like /usr/local/texlive/2011/texmf.cnf.
3. Open this file as root in your favorite text editor (in case you don’t yet have a favorite text editor, I suggest vim), i.e. sudoedit /usr/local/texlive/2011/texmf.cnf is a shortcut for this, although no-one says you cannot use sudo gedit e.g. sudo vim /usr/local/texlive/2011/texmf.cnf but you’ll probably want to replace vim by gedit.
4. Add the following two lines anywhere you like in this file (it’s probably rather empty, containing nothing but comments)

   TEXMFHOME = ~/.texmf
   TEXMFDBS = {!!$TEXMFSYSCONFIG,!!$TEXMFSYSVAR,!!$TEXMFMAIN,!!$TEXMFLOCAL,!!$TEXMFHOME,!!$TEXMFDIST}

   In case you’re interested in what’s so special about this $TEXMFDBS variable: unlike the standard configuration, we have added our non-standard hidden local texmf folder by adding $TEXMFHOME, a variable that’s not there by default but that is not necessary so skip this step.

5. Run updmap, this will update your configuration files. You’ll get a lot of output, hopefully no errors.
6. Run texhash. Its output will look like this

   texhash: Updating /home/.../.texmf/ls-R... 
   texhash: /usr/local/texlive/2011/texmf: directory not writable. Skipping...
   texhash: /usr/local/texlive/2011/texmf-config: directory not writable. Skipping...
   texhash: /usr/local/texlive/2011/texmf-dist: directory not writable. Skipping...
   texhash: /usr/local/texlive/2011/../texmf-local: directory not writable. Skipping...
   texhash: /usr/local/texlive/2011/texmf-var: directory not writable. Skipping...
   texhash: Done.

   As we didn’t run texhash with root privileges, most directories are skipped. Yet the first directory where the dots are replaced by your username looks promising.

7. Mimic the structure of /usr/local/texlive/2011/texmf/, i.e. in my case that means I have to add the beamer theme in the folder ~/.texmf/tex/latex/beamer/themes/theme/ (or possibly some variation on this, but I decided to do it the strict way).

The benefits of this approach are immediately obvious: we can write in our ~/.texmf folder as we like and run texhash without root privileges. And it’s hidden from our view if we don’t bother about hidden files! So we’ve fixed twoone issues:

• TeX Live 2011 defines $TEXMFHOME as ~/texmf but we want it to be invisible so we’ve overridden the value with ~/.texmf.
• TeX Live 2011 ignores $TEXMFHOME for its filename database. Hence your files would never have been found.

What remains is an explanation on how to configure TeX Live 2011 to look in a hidden folder, instead of its default visible folder. The rest can safely be ignored.

Pygments in combination with the minted package is a very powerful syntax highlighter for LaTeX, with the possibility to use colored, bold and italic text. Unfortunately, the Computer Modern Typewriter font includes no bold shapes. Latin Modern does, but the difference is almost unnoticeable. Therefore I prefer Beramono, which in addition is a nice combination with Bitstream Charter. So far my personal taste.

While using this font setup for highlighting Cython code, I discovered a bug in the LatexFormatter of Pygments. When highlighting the following (rather useless) Cython function, the output (with the default Pygments style) is:

cpdef int add(int a, int b):
    return a + b

Actually, this fragment was highlighted with the HTMLFormatter. The LatexFormatter on the other hand outputs something like this:

cpdef int add(int a, int b):
    return a + b

when converted to HTML, obviously. The actual LaTeX code would be

\documentclass{minimal}
\usepackage{fancyvrb}
\usepackage{color}
\usepackage[T1]{fontenc}
\usepackage[scaled]{beramono}

\makeatletter
\def\PY@reset{\let\PY@it=\relax \let\PY@bf=\relax%
    \let\PY@ul=\relax \let\PY@tc=\relax%
    \let\PY@bc=\relax \let\PY@ff=\relax}
\def\PY@tok#1{\csname PY@tok@#1\endcsname}
\def\PY@toks#1+{\ifx\relax#1\empty\else%
    \PY@tok{#1}\expandafter\PY@toks\fi}
\def\PY@do#1{\PY@bc{\PY@tc{\PY@ul{%
    \PY@it{\PY@bf{\PY@ff{#1}}}}}}}
\def\PY#1#2{\PY@reset\PY@toks#1+\relax+\PY@do{#2}}

\def\PY@tok@nf{\def\PY@tc##1{\textcolor[rgb]{0.00,0.00,1.00}{##1}}}
\def\PY@tok@o{\def\PY@tc##1{\textcolor[rgb]{0.40,0.40,0.40}{##1}}}
\def\PY@tok@kt{\def\PY@tc##1{\textcolor[rgb]{0.69,0.00,0.25}{##1}}}
\def\PY@tok@k{\let\PY@bf=\textbf\def\PY@tc##1{\textcolor[rgb]{0.00,0.50,0.00}{##1}}}
\makeatother

\begin{document}

\begin{Verbatim}[commandchars=\\\{\}]
\PY{k}{cpdef} \PY{k+kt}{int} \PY{n+nf}{add}\PY{p}{(}\PY{k+kt}{int} \PY{n}{a}\PY{p}{,} \PY{k+kt}{int} \PY{n}{b}\PY{p}{)}\PY{p}{:}
    \PY{k}{return} \PY{n}{a} \PY{o}{+} \PY{n}{b}
\end{Verbatim}

\end{document}

resulting in this pdf output. As the output differs in the handling of the type keywords a question arises: which Formatter is correct?

Let’s take a look at the style definition in pygments/styles/default.py:

Keyword:      "bold #008000",
Keyword.Type: "nobold #B00040",

Because int is a Keyword.Type, it should not be bold. Simplified, the macro \PY{k+kt}{int} executes \PY@tok@k and \PY@tok@kt before printing \PY@bf{int}. \PY@tok@k sets \PY@bf=\textbf, and \PY@tok@kt does nothing with \PY@bf, so the result is \textbf{int}.

It looks like the LatexFormatter tries to implement inheritance and fails. Funny thing is, inheritance doesn’t need to be implemented, because another part of Pygments already takes care of it. We can replace \PY{k+kt}{int} by \PY{kt}{int}. This can be done in pygments/formatter/latex.py, by replacing

styles = []
while ttype is not Token:
    try:
        styles.append(t2n[ttype])
    except KeyError:
        # not in current style
        styles.append(_get_ttype_name(ttype))
    ttype = ttype.parent
styleval = '+'.join(reversed(styles))

with

try:
    styleval = t2n[ttype]
except KeyError:
    # not in current style
    styleval = _get_ttype_name(ttype)

Additionally, some macro definitions in the preamble can be simplified. This will not change anything visually, but it removes unused features. This can be done by replacing

STYLE_TEMPLATE = r'''
\makeatletter
\def\%(cp)s@reset{\let\%(cp)s@it=\relax \let\%(cp)s@bf=\relax%%
    \let\%(cp)s@ul=\relax \let\%(cp)s@tc=\relax%%
    \let\%(cp)s@bc=\relax \let\%(cp)s@ff=\relax}
\def\%(cp)s@tok#1{\csname %(cp)s@tok@#1\endcsname}
\def\%(cp)s@toks#1+{\ifx\relax#1\empty\else%%
    \%(cp)s@tok{#1}\expandafter\%(cp)s@toks\fi}
\def\%(cp)s@do#1{\%(cp)s@bc{\%(cp)s@tc{\%(cp)s@ul{%%
    \%(cp)s@it{\%(cp)s@bf{\%(cp)s@ff{#1}}}}}}}
\def\%(cp)s#1#2{\%(cp)s@reset\%(cp)s@toks#1+\relax+\%(cp)s@do{#2}}

with

STYLE_TEMPLATE = r'''
\makeatletter
\def\%(cp)s@reset{\let\%(cp)s@it=\relax \let\%(cp)s@bf=\relax%%
    \let\%(cp)s@ul=\relax \let\%(cp)s@tc=\relax%%
    \let\%(cp)s@bc=\relax \let\%(cp)s@ff=\relax}
\def\%(cp)s@tok#1{\csname %(cp)s@tok@#1\endcsname}
\def\%(cp)s@do#1{\%(cp)s@bc{\%(cp)s@tc{\%(cp)s@ul{%%
    \%(cp)s@it{\%(cp)s@bf{\%(cp)s@ff{#1}}}}}}}
\def\%(cp)s#1#2{\%(cp)s@reset\%(cp)s@tok{#1}\%(cp)s@do{#2}}

Now we’ve arrived at the correct version of the backend, but there are still some issues with the CythonLexer. In most cases this will suffice (unless other lexers contain bugs as well), yet for completeness’ sake, I give my version of the CythonLexer. It can be found at 314eter / pygments-CythonLexer.

The result: after all the described modifications, we should arrive at this highlighted piece of code.

As a matter of fact, this issue with the LaTeXFormatter is known to Pygments (by means of this bug report), but they’ve put the issue on hold. If you encounter it, this workaround could be the solution.

And this kids is why you should never dig into TeX, it’s addictive :).