# Listings: consistently colouring numbers

I have been using this solution found here at LaTeX Stack Exchange for colouring numbers in my code excerpts:

\documentclass{article}
\usepackage{listings}
\usepackage{xcolor}

\makeatletter

%%% Copied from https://tex.stackexchange.com/a/500690/23765
% Some conditional tests
\def\@genericif#1{#1\expandafter\@firstoftwo\else\expandafter\@secondoftwo\fi}
\def\@ifdigit#1{\@genericif{\ifnum1<1\noexpand#1\relax}}
\def\@ifempty#1{\@genericif{\if\relax\detokenize{#1}\relax}}

% The main parsing macros
\def\parse@num#1{%
\@ifempty{#1}%
{\parse@num@false}%
{\@genericif{\parsesign}%
{\parse@num@sign#1{}\@end}%
{\parse@num@dig#1{}\@end}%
}%
}
% Parse sign
\def\parse@num@sign#1#2\@end{%
\@genericif{\ifx\parse@num@minus#1}%
{\@ifempty{#2}{\parse@num@false}{\parse@num@dig#2\@end}}%
{\@genericif{\ifx\parse@num@plus#1}%
{\@ifempty{#2}{\parse@num@false}{\parse@num@dig#2\@end}}%
{\parse@num@dig#1#2\@end}%
}%
}
% Parse first digit
\def\parse@num@dig#1#2\@end{%
\@ifdigit{#1}%
{\@ifempty{#2}{\parse@num@true}{\parse@num@digs#2\@end}}%
{\parse@num@false}%
}
% Parse optional following digits
\def\parse@num@digs#1#2\@end{%
\@ifdigit{#1}{%
\@ifempty{#2}%
{\parse@num@true}%
{\parse@num@digs#2\@end}%
}{%
\@genericif{\parsefloat}{%
\@genericif{\ifx\parse@num@point#1}%
{\@ifempty{#2}{\parse@num@false}{\parse@num@decs#2\@end}}%
{\parse@num@false}%
}{\parse@num@false}%
}%
}
% Parse decimal places
\def\parse@num@decs#1#2\@end{%
\@ifdigit{#1}{%
\@ifempty{#2}%
{\parse@num@true}%
{\parse@num@decs#2\@end}%
}{\parse@num@false}%
}

% User interface
\newcommand\ifnumber[4][]{%
\begingroup
\let\parsesign=\iftrue
\let\parsefloat=\iftrue
\let\parse@num@minus=-%
\let\parse@num@plus=+%
\let\parse@num@point=.%
#1%
\def\parse@num@true{\endgroup#3}%
\def\parse@num@false{\endgroup#4}%
\parse@num{#2}%
}

%%% Additions to the listings package
\lst@Key{parsenumbers}{false}[t]{\lstKV@SetIf{#1}\lst@ifparsenumbers}

\lst@ifparsenumbers
% Only if mode changes are not prohibited
\lst@ifmode\else
\expandafter\@hook@ifnumber\the\lst@token\@end
{}%
\fi
\fi
}
\def\@hook@ifnumber#1#2\@end{%
\@genericif{\ifx\lst@nolig#1}%
{\@hook@ifnumber@{#2}}%
{\@hook@ifnumber@{#1#2}}%
}
\def\@hook@ifnumber@{%
\ifnumber[\expandafter\let\expandafter\parse@num@minus\csname lst@um-\endcsname]%
}

\makeatother

%%% Example document
\lstset{
basicstyle = \ttfamily,
identifierstyle = \color{blue},
keywordstyle = \color{green!80!black},
keywords = {foo},
moredelim = [il][]{**},
moredelim = [l][\color{gray}]{/},
morestring = [d][\color{gray}]{"},
morestring = *[d][\color{gray}\itshape]{!},
morestring = **[d][\color{gray}\itshape]{?},
% Apply new number coloring routine
parsenumbers = true,
}


It works fairly well but unfortunately it also does have some issues. Appending this above my minimal example below...:

\begin{document}

\section{Python}

\begin{lstlisting}
def foobar(self):
var = 123 + 456
var_2 = 4.56
var3 = 789
for _ in range(3):
print(test)
if var_2 > 1.23:
print(1024)
elif (var3 <= 1000 and var_2 is None):
print(0)
\end{lstlisting}

\section{Processing}

\begin{lstlisting}
void setup() {
size(300, 300);
background(0, 200, 0);
}

void draw() {
drawFlower(150, 150, 100);
for (int i = 0; i < 80; i = i+5) {
line(30, i, 80, i);
}
x = x + 0.1;
y = 0.1 + y;
if (x > 1.23) {
x = 0;
y = 0 ;
}
}
\end{lstlisting}

\end{document}


...results in:

The results are not bad, and it's particularly good that that solution handles numbers in variable names regardless if they are followed by an underline or not (e.g. var_2 and var3). But the example above also show a couple of problems which I have not been able to fix:

• It's possible to see that numbers preceded by a ( or immediately followed by ) are not coloured, e.g. range(3), size(300, 300)
• numbers touching signs such as commas, colons, or semicolons are not coloured either; e.g. the middle number in background(0, 200, 0);, or the numbers in x = x + 0.1; or if var_2 > 1.23:
• on the other hand, having spaces around them result in proper highlight, e.g. y = 0 ; (with space before semicolon) or the number 1000 in elif (var3 <= 1000 and var_2 is None):

Would anyone be able to help me tweak this snippet so that the numbers are consistently highlighted in these situations while still not being highlighted in variable and function names?

Edit: in a nutshell, I would like numbers to be highlighted if:

• they come after any of the following characters:  , ., (, {,[, :
• they come before any of the following characters:  , ., ), }, ], :, ;
• but definitely not include _ in either group as that might break the variable naming convention in many snippets of code (even though Python does accept _ in numbers to aid the visual identification of groups of 10^3, as in x = 1_000_000.

Currently, the code above only correctly identifies   and . from all the characters mentioned in the bullet points above.

Edit: unfortunately minted is not an option for me, it does not play along well with my dissertation file.

Consider using minted and customize the stylesheets.

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{minted}

\usemintedstyle{colorful}

\begin{document}

\begin{minted}{python}
def foobar(self):
var = 123 + 456
var_2 = 4.56
var3 = 789
for _ in range(3):
print(test)
if var_2 > 1.23:
print(1024)
elif (var3 <= 1000 and var_2 is None):
print(0)
\end{minted}

\begin{minted}{c}
void setup() {
size(300, 300);
background(0, 200, 0);
}

void draw() {
drawFlower(150, 150, 100);
for (int i = 0; i < 80; i = i+5) {
line(30, i, 80, i);
}
x = x + 0.1;
y = 0.1 + y;
if (x > 1.23) {
x = 0;
y = 0 ;
}
}
\end{minted}

\end{document}

• Thank you for you reply, I really appreciate it. Unfortunately I have a quite complex file for my dissertation with tons of customisations and I was not able to get minted to play along nicely with it. My own listings is already very customised for all the code I use, so ideally I was looking for a solution that simply involved tweaking that snippet I posted. It comes very close to getting the job done, so I was hoping someone with sufficient knowledge of LaTeX customisation could perhaps give me a hand tweaking it. – gilbertohasnofb Nov 7 '20 at 20:41
• In this case, you can maybe tweak the outputs manually with escapeinside, where you can set the colors with \color command. As for minted, its backend is pygments, which is also highly customizable. – Alan Xiang Nov 7 '20 at 21:02
• That is definitely an option, albeit my last one as I have a ton of code in my Appendix, and their files are automatically generated by a Makefile during the LaTeX build. In that case I would probably just not use number colouring at all. I am still hoping someone can spot how to adapt the code above to include not only periods in its rules, but also the other glyphs I mentioned. – gilbertohasnofb Nov 9 '20 at 17:54

If I understood the question you want to color all digits unless they are in keywords or identifiers. You could do this by using as base font a font which has colored digits, and a different font for the keywords. With lualatex this here is possible:

\documentclass{article}
\usepackage{listings,xcolor}
\usepackage{fontspec}

\directlua{
{
["FF00FF"] = {"one","two","three","four","five","six","seven","eight","nine","zero"},
})}

\newfontfamily\colordigits{Latin Modern Mono}[RawFeature={color=colordigits}]

\lstset{
basicstyle = \colordigits,
identifierstyle = \ttfamily\color{blue},
keywordstyle = \ttfamily\color{green!80!black},
keywords = {foo},
moredelim = [il][]{**},
moredelim = [l][\color{gray}]{/},
morestring = [d][\color{gray}]{"},
morestring = *[d][\color{gray}\itshape]{!},
morestring = **[d][\color{gray}\itshape]{?},
}
%
\begin{document}

\begin{lstlisting}
def foobar(self):
var = 123 + 456
var_2 = 4.56
var3 = 789
for _ in range(3):
print(test)
if var_2 > 1.23:
print(1024)
elif (var3 <= 1000 and var_2 is None):
print(0)
\end{lstlisting}

\section{Processing}

\begin{lstlisting}
void setup() {
size(300, 300);
background(0, 200, 0);
}

void draw() {
drawFlower(150, 150, 100);
for (int i = 0; i < 80; i = i+5) {
line(30, i, 80, i);
}
x = x + 0.1;
y = 0.1 + y;
if (x > 1.23) {
x = 0;
y = 0 ;
}
}
\end{lstlisting}

\end{document}


• This is such a clever solution! Do you know if it would be possible to accomplish something similar with PdfLaTeX, i.e. overwrite the colour of some characters on a custom font? I'm at a quite late stage with my dissertation and I would prefer to keep using the same engine. – gilbertohasnofb Nov 14 '20 at 17:01
• I don't know, perhaps it would possible to add color specials with a virtual font, but trying this out and setting it then up would probably cost more time than converting your dissertation to lualatex. – Ulrike Fischer Nov 14 '20 at 17:12
• Thank you so much once again. Unfortunately I am running into errors when trying to compile your example above. It seems that the version of LuaTeX available through texlive in my system (Mint 18.3) might be too old for this command. I read that there's a PPA with a slightly newer version of texlive, but there is danger of packages being broken, which would not be fun at this stage. I appreciate your help nevertheless. – gilbertohasnofb Nov 14 '20 at 18:03

For completeness, a non-Lua solution using interchartoks in xetex fails at the last moment because lstlistings inserts glue between tokens. Glue is seen as an interword-boundary marker by interchartoks.

So not an answer (without a package re-write (using zero-width joiners?), even if the pdflatex scenario were surmountable.

To illustrate the transitions between token classes:

red is word-boundary to digit transition.

MWE

\documentclass{article}
\XeTeXinterchartokenstate=1
\usepackage{listings,xcolor}
\usepackage{fontspec}

\newXeTeXintercharclass\LetterClass

%from:
%https://tex.stackexchange.com/questions/411846/xelatex-minion-pro-and-italian-apostrophe-kerning/411850#411850
\makeatletter
\@tempcnta=\A
\loop\unless\ifnum\@tempcnta>\Z
\XeTeXcharclass \@tempcnta \LetterClass
\repeat
\@tempcnta=\a
\loop\unless\ifnum\@tempcnta>\z
\XeTeXcharclass \@tempcnta \LetterClass
\repeat
\XeTeXcharclass \_ \LetterClass

\makeatother

% char class for digits
\newXeTeXintercharclass \mydigitsclass
\XeTeXcharclass \0 \mydigitsclass
\XeTeXcharclass \1 \mydigitsclass
\XeTeXcharclass \2 \mydigitsclass
\XeTeXcharclass \3 \mydigitsclass
\XeTeXcharclass \4 \mydigitsclass
\XeTeXcharclass \5 \mydigitsclass
\XeTeXcharclass \6 \mydigitsclass
\XeTeXcharclass \7 \mydigitsclass
\XeTeXcharclass \8 \mydigitsclass
\XeTeXcharclass \9 \mydigitsclass

% def interchartokes

\XeTeXinterchartoks \LetterClass \mydigitsclass = {\begingroup\huge}
\XeTeXinterchartoks \mydigitsclass \LetterClass  = {\endgroup}

\XeTeXinterchartoks 0 \mydigitsclass = {\begingroup\color{green}}
\XeTeXinterchartoks \mydigitsclass 0  = {\endgroup}
\XeTeXinterchartoks 4095 \mydigitsclass = {\begingroup\color{red}}
\XeTeXinterchartoks \mydigitsclass 4095  = {\endgroup}

\lstset{
%    basicstyle = \colordigits,
identifierstyle = \ttfamily\color{blue},
keywordstyle = \ttfamily\color{green!80!black},
keywords = {foo},
moredelim = [il][]{**},
moredelim = [l][\color{gray}]{/},
morestring = [d][\color{gray}]{"},
morestring = *[d][\color{gray}\itshape]{!},
morestring = **[d][\color{gray}\itshape]{?},
}

\begin{document}
\XeTeXinterchartokenstate=0
\section{Test}
\XeTeXinterchartokenstate=1
abc 012 345 678 9 xyz

[The lstlisting environment adds "\textbackslash glue 0 plus 1fil minus 1fil" betweeen every token]

%https://tex.stackexchange.com/questions/281566/xetex-special-xetexcharclass-needed-for-null-glues/321664#321664
\XeTeXinterchartokenstate=0
\subsection{Inline}
\XeTeXinterchartokenstate=1
def foobar(self):
var = 123 + 456
var\_2 = 4.56
var3 = 789
for \_ in range(3):
print(test)
if var\_2 > 1.23:
print(1024)

\XeTeXinterchartokenstate=0
\subsection{Verbatim}
\XeTeXinterchartokenstate=1
\begin{verbatim}
def foobar(self):
var = 123 + 456
var_2 = 4.56
var3 = 789
for _ in range(3):
print(test)
if var_2 > 1.23:
print(1024)
\end{verbatim}

\XeTeXinterchartokenstate=0
\subsection{Listing}
\XeTeXinterchartokenstate=1
\begin{lstlisting}
def foobar(self):
var = 123 + 456
var_2 = 4.56
var3 = 789
for _ in range(3):
print(test)
if var_2 > 1.23:
print(1024)
elif (var3 <= 1000 and var_2 is None):
print(0)
\end{lstlisting}

\XeTeXinterchartokenstate=0
\section{Processing}
\XeTeXinterchartokenstate=1

\begin{lstlisting}
void setup() {
size(300, 300);
background(0, 200, 0);
}

void draw() {
drawFlower(150, 150, 100);
for (int i = 0; i < 80; i = i+5) {
line(30, i, 80, i);
}
x = x + 0.1;
y = 0.1 + y;
if (x > 1.23) {
x = 0;
y = 0 ;
}
}
\end{lstlisting}

\end{document}
`