% \iffalse -*- coding: utf-8 ; -*- \fi \iffalse meta-comment
%
% Copyright (C) 2022 by F. Pantigny
% -----------------------------------
%
% This file may be distributed and/or modified under the
% conditions of the LaTeX Project Public License, either version 1.3
% of this license or (at your option) any later version.
% The latest version of this license is in:
%
% http://www.latex-project.org/lppl.txt
%
% and version 1.3 or later is part of all distributions of LaTeX
% version 2005/12/01 or later.
%
% \fi
% \iffalse
\def\myfileversion{0.8}
\def\myfiledate{2022/10/23}
%
%
%<*batchfile> 
\begingroup
\input l3docstrip.tex
\keepsilent
\usedir{tex/latex/cascade}
\preamble

Copyright (C) 2022 by F. Pantigny
-----------------------------------

This file may be distributed and/or modified under the
conditions of the LaTeX Project Public License, either version 1.3
of this license or (at your option) any later version.
The latest version of this license is in:

http://www.latex-project.org/lppl.txt

and version 1.3 or later is part of all distributions of LaTeX
version 2005/12/01 or later.

\endpreamble
\askforoverwritefalse
\endgroup
%</batchfile>
%
%<@@=piton>
%<*driver>
\documentclass{l3doc}
\usepackage{geometry}
\geometry{left=2.8cm,right=2.8cm,top=2.5cm,bottom=2.5cm,papersize={21cm,29.7cm}}
\usepackage{fontspec}
\usepackage[dvipsnames]{xcolor}
\usepackage{caption,tabularx}
\def\emphase{\bgroup\color{RoyalPurple}\let\next=}
\fvset{commandchars=\~\#\@,formatcom=\color{gray}}
\captionsetup{labelfont = bf}
\usepackage{ragged2e}
\usepackage[footnotehyper,escape-inside=$$]{piton} % $$

\def\interitem{\vskip 7mm plus 2 mm minus 3mm}          
\parindent 0pt
\skip\footins = 2\bigskipamount

\PitonOptions{gobble=2}

\EnableCrossrefs

\begin{document}
\DocInput{piton.dtx}
\end{document}
%</driver>

% \fi
% \title{The package \pkg{piton}\thanks{This document corresponds to the
% version~\myfileversion\space of \pkg{piton}, at the date of~\myfiledate.}} 
% \author{F. Pantigny \\ \texttt{fpantigny@wanadoo.fr}}
%
% \maketitle
%
% \begin{abstract}
% The package \pkg{piton} provides tools to typeset Python listings with
% syntactic highlighting by using the Lua library LPEG. It requires LuaLaTeX.
% \end{abstract}
% 
% 
% \section{Presentation}
% 
%
% The package \pkg{piton} uses the Lua library LPEG\footnote{LPEG is a
% pattern-matching library for Lua, written in C, based on \emph{parsing
% expression grammars}: \url{http://www.inf.puc-rio.br/~roberto/lpeg/}} for
% parsing Python listings and typeset them with syntactic highlighting. Since it
% uses Lua code, it works with |lualatex| only (and won't work with the other
% engines: |latex|, |pdflatex| and |xelatex|). It does not use external program
% and the compilation does not require |--shell-escape|. The compilation is very
% fast since all the parsing is done by the library LPEG, written in C.
% 
% \bigskip
% Here is an exemple of code typeset by \pkg{piton}, with the environment |{Piton}|.
%
% \bigskip
%
%    \begin{Piton}
% from math import pi
%
% def arctan(x,n=10):
%     '''Compute the value of arctan(x)
%        n is the number of terms of the sum'''
%     if x < 0:
%         return -arctan(-x) # recursive call
%     elif x > 1: 
%         return pi/2 - arctan(1/x) 
%         ## (we have used that $\arctan(x)+\arctan(1/x)=\frac{\pi}{2}$ for $x>0$)\footnote{This LaTeX escape has been done by beginning the comment by \ttfamily\#\#.}
%     else: 
%         s = 0
%         for k in range(n):
%             s += (-1)**k/(2*k+1)*x**(2*k+1)
%         return s 
%    \end{Piton}
% 
%
% \bigskip
% 
% The package \pkg{piton} is entirely contained in the file
% |piton.sty|. This file may be put in the current directory or in a
% |texmf| tree. However, the best is to install \pkg{piton} with a TeX
% distribution such as MiKTeX, TeX Live or MacTeX.
% 
% 
% \section{Use of the package}
%
% The package \pkg{piton} should be loaded with the classical command
% |\usepackage|: |\usepackage{piton}|.
%
% \smallskip
% Nevertheless, we have two remarks:
% \begin{itemize}
% \item the package \pkg{piton} uses the package \pkg{xcolor} (but \pkg{piton}
% does \emph{not} load \pkg{xcolor}: if \pkg{xcolor} is not loaded before the
% |\begin{document}|, a fatal error will be raised).
% \item the package \pkg{piton} must be used with LuaLaTeX exclusively: if
% another LaTeX engine (|latex|, |pdflatex|, |xelatex|,\dots ) is used, a
% fatal error will be raised.
% \end{itemize}
% 
% \medskip
% The package \pkg{piton} provides three tools to typeset Python code: the
% command |\piton|, the environment |{Piton}| and the command |\PitonInputFile|.
%
% \begin{itemize}
% \item The command |\piton| should be used to typeset small pieces of code
% inside a paragraph. \emph{Caution}: That fonction takes in its argument
% \emph{verbatim}. Therefore, it cannot be used in the argument of another
% command (however, it can be used within an environment).
% \item The environment |{Piton}| should be used to typeset multi-lines code.
% For sake of customization, it's possible to define new environments similar to
% the environment |{Piton}| with the command |\NewPitonEnvironment|:
% cf.~\ref{NewPitonEnvironment} p.~\pageref{NewPitonEnvironment}.
% \item The command |\PitonInputFile| is used to insert and typeset a whole
% external file.
% \end{itemize}
%
% \bigskip
% It's possible to compose comments in LaTeX by beginning them with |##| (it's a
% ``LaTeX escape''). The characters |##| themselves won't be printed and the
% spaces after |##| are removed. These comments will be called ``LaTeX
% comments'' in this document.
% 
% \section{Customization}
%
% \subsection{The command \textbackslash PitonOptions}
%
% The command |\PitonOptions| takes in as argument a comma-separated list of
% \textsl{key=value} pairs. The scope of the settings done by that command is
% the current TeX group.\footnote{We remind that an LaTeX environment is, in
% particular, a TeX group.}
%
% \begin{itemize}
% \item The key |gobble| takes in as value a positive integer~$n$: the first $n$
% characters are discarded (before the process of highlightning of the code) for
% each line of the environment |{Piton}|.
%
% \item Then the key |auto-gobble| is in force, the extension \pkg{piton} computes
% the minimal value $n$ of the number of consecutives space beginning each (non
% empty) line of the environment |{Piton}| and applies |gobble| with that value
% of~$n$.
%
% \item When the key |env-gobble| is in force, \pkg{piton} applies |gobble| with
% a value of $n$ equal to the number of spaces before |\end{Piton}| on the last
% line (if that line contains only spaces). The name of that key comes from
% \emph{environment gobble}: the effect of gobble is set by the position of the
% commands |\begin{Piton}| and |\end{Piton}| which delimit the current environment.
%
% \item With the key |line-numbers|, the \emph{non empty} lines are numbered in
% the environments |{Piton}| and in the listings resulting from the use of
% |\PitonInputFile|.
% 
% \item With the key |all-line-numbers|, \emph{all} the lines are numbered,
% including the empty ones.
%
% \item By default, the counter of lines is set to zero at the beginning of each
% environment |{Piton}| or use of |\PitonInputFile|. With the key |resume|, that
% reinitialisation is not done.
%
% \item The key |splittable| allows pages breaks within the environments
% |{Piton}| and the listings produced by 
% |\PitonInputFile|. 
%
% \item The key |background-color| sets the background color of the environments
% |{Piton}| and the listings produced by |\PitonInputFile| (that background has
% a width of |\linewidth|). Even with a background color, the pages breaks are
% allowed, as soon as the key |splittable| is in force.\footnote{The
% environments \texttt{\{Piton\}} are breakable, even within a breakable
% environment of \pkg{tcolorbox}. Remind that an environment of \pkg{tcolorbox}
% included in another environment of \pkg{tcolorbox} is \emph{not} breakable,
% even when both environments use the key |breakable| of \pkg{tcolorbox}.}
%
% \item \colorbox{yellow!50}{\textbf{New 0.8}}\enskip The key |left-margin|
% corresponds to a margin on the left. That key may be useful in conjonction
% with the key |line-numbers| or the key |line-all-numbers| if one does not want
% the numbers in an overlapping position on the left.
% \end{itemize}
%
% \bigskip
%
% \begingroup
% \fvset{commandchars=\~\&\@,formatcom=\small\color{gray}}
% \begin{Verbatim}
% ~emphase&\PitonOptions{line-numbers,auto-gobble,background-color = gray!15}@
% \begin{Piton}
%     from math import pi
%
%     def arctan(x,n=10):
%         '''Compute the value of arctan(x)
%            n is the number of terms of the sum'''
%         if x < 0:
%             return -arctan(-x) # recursive call
%         elif x > 1: 
%             return pi/2 - arctan(1/x) 
%             ## (we have used that $\arctan(x)+\arctan(1/x)=\frac{\pi}{2}$ pour $x>0$)
%         else 
%             s = 0
%             for k in range(n):
%                 s += (-1)**k/(2*k+1)*x**(2*k+1)
%             return s 
% \end{Piton}
% \end{Verbatim}
% \endgroup
%
% \begingroup
% \PitonOptions{line-numbers,background-color = gray!15}
%    \begin{Piton}
% from math import pi
%
% def arctan(x,n=10):
%     '''Compute the value of arctan(x)
%        n is the number of terms of the sum'''
%     if x < 0:
%         return -arctan(-x) # recursive call
%     elif x > 1: 
%         return pi/2 - arctan(1/x) 
%         ## (we have used that $\arctan(x)+\arctan(1/x)=\frac{\pi}{2}$ for $x>0$)
%     else 
%         s = 0
%         for k in range(n):
%             s += (-1)**k/(2*k+1)*x**(2*k+1)
%         return s 
%    \end{Piton}
% \endgroup
% 
% \subsection{The key escape-inside}
%
% The key |escape-inside| must be used when loading the package \pkg{piton}
% (that is to say in the instruction |\usepackage|). For technical reasons, it
% can't be used in the command |\PitonOptions|. That option takes in as value
% two characters which will be used to delimit pieces of code which will
% thrown directly to LaTeX (and composed by LaTeX).
%
% \medskip
% In the following example, we assume that the extension \pkg{piton} has been
% loaded by the following instruction.
%
% \begin{Verbatim}
% \usepackage[~emphase#escape-inside=$$@]{piton}
% \end{Verbatim}
%
% \medskip
% In the following code, which is a recursive programmation of the mathematical
% factorial, we decide to highlight in yellow the instruction which contains the
% recursive call. 
% \begin{Verbatim}
% \begin{Piton}
% def fact(n):
%     if n==0:
%         return 1
%     else:
%         ~emphase#$\colorbox{yellow!50}{$@return n*fact(n-1)~emphase#$}$@
% \end{Piton}
% \end{Verbatim}
%
%    \begin{Piton}
% def fact(n):
%     if n==0:
%         return 1
%     else:
%         $\colorbox{yellow!50}{$return n*fact(n-1)$}$
%    \end{Piton}
%         
% \bigskip
%
% \emph{Caution} : The escape to LaTeX allowed by the characters of
% |escape-inside| is not active in the strings nor in the Python comments
% (however, it's possible to have a whole Python comment composed in LaTeX by
% beginning it with |##|; such comments are merely called ``LaTeX comments'' in
% this document). 
%
%
% \subsection{The styles}
%
% \label{styles}
%
% The package \pkg{piton} provides the command |\SetPitonStyle| to customize the
% different styles used to format the syntactic elements of the Python listings.
% The customizations done by that command are limited to the current TeX
% group.\footnote{We remind that an LaTeX environment is, in particuilar, a TeX group.}
%
% \bigskip
% The command |\SetPitonStyle| takes in as argument a comma-separated list of
% \textsl{key=value} pairs. The keys are names of styles and the value are LaTeX
% formatting instructions.
%
% \bigskip
% These LaTeX instructions must be formatting instructions such as
% |\color{...}|, |\bfseries|, |\slshape|, etc. (the commands of this kind are
% sometimes called \emph{semi-global} commands). It's also possible to put,
% \emph{at the end of the list of instructions}, a LaTeX command taking exactly
% one argument.
% 
% \bigskip
% Here an example which changes the style used to highlight, in the definition
% of a Python function, the name of the function which is defined.
%
% \begin{verbatim}
% \SetPitonStyle 
%   { Name.Function = \bfseries \setlength{\fboxsep}{1pt}\colorbox{yellow!50} }
% \end{verbatim}
%
% In that example, |\colorbox{yellow!50}| must be considered as the name of a
% LaTeX command which takes in exactly one argument, since, usually, it is used
% with the syntax |\colorbox{yellow!50}{...}|.
%
% \medskip
% \begingroup
% \SetPitonStyle 
%   { Name.Function = \bfseries \setlength{\fboxsep}{1pt}\colorbox{yellow!50} }
% With that setting, we will have : \piton{def cube(x) : return x * x * x }
% \endgroup
% 
% \bigskip
% The different styles are described in the table \ref{Semantic}. The initial
% settings done by \pkg{piton} in |piton.sty| are inspired by the style
% \pkg{manni} de Pygments.\footnote{See: \url{https://pygments.org/styles/}.
% Remark that, by default, Pygments provides for its style \pkg{manni} a colored
% background whose color is the HTML color \texttt{\#F0F3F3}.}
%
%
%
% \begin{table}[b]
% \centering
% \caption{Usage of the different styles}
% \label{Semantic}
% \begin{tabular}{@{}>{\ttfamily}l>{\RaggedRight\arraybackslash}p{9cm}@{}}
% \toprule
% \normalfont Style  & Usage \\
% \midrule
% Number & the numbers \\
% String.Short & the short strings (between \texttt{'} or \verb|"|) \\
% String.Long & the long strings (between \texttt{'''} or \verb|"""|) except the
% documentation strings \\ 
% String & that keys sets both |String.Short| and |String.Long| \\
% String.Doc & the documentation strings \\
% String.Interpol & the syntactic elements of the fields of the f-strings (that
% is to say the characters \texttt{\{}, \texttt{\}} and \texttt{:}) \\
% Operator & the following operators : \texttt{!= == << >> - \~{} + / * \% = < > \& .} \verb+|+ \verb|@|\\
% Operator.Word & the following operators : \texttt{in}, \texttt{is},
% \texttt{and}, \texttt{or} and \texttt{not} \\ 
% Name.Builtin & the predefined functions of Python \\
% Name.Function & the name of the functions defined by the user, at the point of
% their definition (that is to say after the keyword |def|) \\
% Name.Decorator & the decorators (instructions beginning by \verb|@| in the classes) \\
% Name.Namespace & the name of the modules (= external libraries) \\
% Name.Class & the name of the classes at the point of their definition \\
% Exception & the names of the exceptions (eg: \texttt{SyntaxError}) \\
% Comment & the comments beginning with \verb|#| \\
% Comment.LaTeX & the comments beginning by \verb|##| which are composed in LaTeX by
% \pkg{piton} (and called merely ``LaTeX comments'' in this document) \\
% Keyword.Constant & |True|, |False| and |None| \\
% Keyword & the following keywords :
%           \ttfamily assert, break, case, continue, del,
%           elif, else, except, exec, finally, for, from, 
%           global, if, import, lambda, non local,
%           pass, raise, return, try, while,
%           with, yield, yield from.\\
% \bottomrule 
% \end{tabular}
% \end{table}
%
%
%
% 
% \subsection{Creation of new environments}
%
% \label{NewPitonEnvironment}
% 
% Since the environment |{Piton}| has to catch its body in a special way (more
% or less as verbatim text), it's not possible to construct new environments
% directly over the environment |{Piton}| with the classical commands
% |\newenvironment| or |\NewDocumentEnvironment|.
%
% That's why \pkg{piton} provides a command |\NewPitonEnvironment|. That
% command takes in three mandatory arguments. 

% That command has the same syntax as the classical environment
% |\NewDocumentEnvironment|.
% 
% \bigskip
% With the following instruction, a new environment |{Python}| will be
% constructed with the same behaviour as |{Piton}|:
%
% {\color{gray}\verb|\NewPitonEnvironment{Python}{}{}{}|}
%
% \bigskip
% If one wishes an environment |{Python}| with takes in as optional argument
% (between square brackets) the keys of the command |\PitonOptions|, it's
% possible to program as follows:
%
% {\color{gray}\verb|\NewPitonEnvironment{Python}{O{}}{\PitonOptions{#1}}{}|}
% 
% \bigskip
% If one wishes to format Python code in a box of \pkg{tcolorbox}, it's possible
% to define an environment |{Python}| with the following code: 
%
%\begin{verbatim}
% \NewPitonEnvironment{Python}{}
%   {\begin{tcolorbox}}
%   {\end{tcolorbox}}
% \end{verbatim}
%
%
% \section{Advanced features}
%
% \subsection{Footnotes in the environments of piton}
% 
% \label{footnote}
% If you want to put footnotes in an environment |{Piton}| or
% (or, more unlikely, in a listing produced by |\PitonInputFile|), you can use a
% pair |\footnotemark|--|\footnotetext|. 
%
% \smallskip
% It's also possible to extract the footnotes with the help of the package
% \pkg{footnote} or the package \pkg{footnotehyper}.
%
% \smallskip
% If \pkg{piton} is loaded with the option |footnote| (with
% |\usepackage[footnote]{piton}| or with |\PassOptionsToPackage|), the
% package \pkg{footnote} is loaded (if it is not yet loaded) and it is used to
% extract the footnotes.
%
% \smallskip
% If \pkg{piton} is loaded with the option |footnotehyper|, the package
% \pkg{footnotehyper} is loaded (if it is not yet loaded) ant it is used to
% extract footnotes.
%
% \smallskip
% Caution: The packages \pkg{footnote} and \pkg{footnotehyper} are incompatible.
% The package \pkg{footnotehyper} is the successor of the package \pkg{footnote}
% and should be used preferently. The package \pkg{footnote} has some drawbacks,
% in particular: it must be loaded after the package \pkg{xcolor} and it is not
% perfectly compatible with \pkg{hyperref}.
%
% \medskip
% In this document, the package \pkg{piton} has been loaded with the option
% |footnotehyper|: see the first page of this document for an example of a
% footnote in an environment |{Piton}|.
%
%
% \section{Examples}
%
%
% \subsection{Line numbering}
%
% By default, the numbers of the lines are composed by \pkg{piton} in an
% overlapping position on the left (by using internally the command |\llap| of LaTeX).
%
% In order to avoid that overlapping, it's necessary to reserve a place for the
% number of the lines with the key |left-margin|.
%
%
%
% \begingroup
% \fvset{commandchars=\~\&\@,formatcom=\small\color{gray}}
% \begin{Verbatim}
% ~emphase&\PitonOptions{background-color=gray!10, left-margin = 5mm, line-numbers}@
% \begin{Piton}
% def arctan(x,n=10):
%     if x < 0:
%         return -arctan(-x)        ## (appel récursif)
%     elif x > 1: 
%         return pi/2 - arctan(1/x) ## (autre appel récursif) 
%     else: 
%         return sum( (-1)**k/(2*k+1)*x**(2*k+1) for k in range(n) ) 
% \end{Piton}
% \end{Verbatim}
% \endgroup
%
%
%
% \begingroup
% \PitonOptions{background-color=gray!10,left-margin = 5mm, line-numbers}
% \begin{Piton}
% def arctan(x,n=10):
%     if x < 0:
%         return -arctan(-x)        ## (appel récursif)
%     elif x > 1: 
%         return pi/2 - arctan(1/x) ## (autre appel récursif) 
%     else: 
%         return sum( (-1)**k/(2*k+1)*x**(2*k+1) for k in range(n) ) 
% \end{Piton}
% \endgroup
%
%
%
%
% \subsection{Formatting of the LaTeX comments}
%
% It's possible to modify the style |Comment.LaTeX| (with |\SetPitonStyle|) in
% order to display the LaTeX comments (which begin with |##|) aligned on the
% right margin.
%
%
% \begingroup
% \fvset{commandchars=\~\&\@,formatcom=\small\color{gray}}
% \begin{Verbatim}
% \PitonOptions{background-color=gray!10}
% ~emphase&\SetPitonStyle{Comment.LaTeX = \hfill \normalfont\color{gray}}@
% \begin{Piton}
% def arctan(x,n=10):
%     if x < 0:
%         return -arctan(-x)        ## appel récursif
%     elif x > 1: 
%         return pi/2 - arctan(1/x) ## autre appel récursif 
%     else: 
%         return sum( (-1)**k/(2*k+1)*x**(2*k+1) for k in range(n) ) 
% \end{Piton}
% \end{Verbatim}
% \endgroup
%
% \begingroup
% \PitonOptions{background-color=gray!10}
% \SetPitonStyle{Comment.LaTeX = \hfill \normalfont\color{gray}}
% \begin{Piton}
% def arctan(x,n=10):
%     if x < 0:
%         return -arctan(-x)        ## appel récursif
%     elif x > 1: 
%         return pi/2 - arctan(1/x) ## autre appel récursif 
%     else: 
%         return sum( (-1)**k/(2*k+1)*x**(2*k+1) for k in range(n) ) 
% \end{Piton}
% \endgroup
%
%
% \vspace{1cm}
% It's also possible to display these LaTeX comments in a kind of second column
% by limiting the width of the Python code by an environment |{minipage}| of LaTeX.
%
%
% \begingroup
% \fvset{commandchars=\~\&\@,formatcom=\small\color{gray}}
% \begin{Verbatim}
% \PitonOptions{background-color=gray!10}
% ~emphase&\NewDocumentCommand{\MyLaTeXCommand}{m}{\hfill \normalfont\itshape\rlap{\quad #1}}@
% ~emphase&\SetPitonStyle{Comment.LaTeX = \MyLaTeXCommand}@
% ~emphase&\begin{minipage}{12cm}@
% \begin{Piton}
% def arctan(x,n=10):
%     if x < 0:
%         return -arctan(-x)       ## appel récursif
%     elif x > 1: 
%         return pi/2 - arctan(1/x) ## autre appel récursif 
%     else: 
%         s = 0
%         for k in range(n):
%              s += (-1)**k/(2*k+1)*x**(2*k+1)
%         return s 
% \end{Piton}
% ~emphase&\end{minipage}@
% \end{Verbatim}
% \endgroup
%
%
%
% \begingroup
% \PitonOptions{background-color=gray!10}
% \NewDocumentCommand{\MyLaTeXCommand}{m}{\hfill \normalfont\itshape\rlap{\quad #1}}
% \SetPitonStyle{Comment.LaTeX = \MyLaTeXCommand}
% \begin{minipage}{12cm}
% \begin{Piton}
% def arctan(x,n=10):
%     if x < 0:
%         return -arctan(-x)       ## appel récursif
%     elif x > 1: 
%         return pi/2 - arctan(1/x) ## autre appel récursif 
%     else: 
%         s = 0
%         for k in range(n):
%              s += (-1)**k/(2*k+1)*x**(2*k+1)
%         return s 
% \end{Piton}
% \end{minipage}
% \endgroup
%
%
%
% \subsection{Notes in the listings}
%
% In order to be able to extract the notes (which are typeset with the command
% |\footnote|, the extension \pkg{piton} must be loaded with the key |footnote|
% or the key |footenotehyper| as explained in the section \ref{footnote}
% p.~\pageref{footnote}. In this document, the extension \pkg{piton} has been
% loaded with the key |footnotehyper|.
%
% Of course, in an environment |{Piton}|, a command |\footnote| may appear only
% within a LaTeX comment (which begins with |##|). It's possible to have comments
% which contain only that command |\footnote|. That's the case in the following example.
%
%
%
% \begingroup
% \fvset{commandchars=\~\&\@,formatcom=\small\color{gray}}
% \begin{Verbatim}
% \PitonOptions{background-color=gray!10}
% \begin{Piton}
% def arctan(x,n=10):
%     if x < 0:
%         return -arctan(-x)~emphase&##\footnote{First recursive call.}]@
%     elif x > 1: 
%         return pi/2 - arctan(1/x)~emphase&##\footnote{Second recursive call.}@
%     else: 
%         return sum( (-1)**k/(2*k+1)*x**(2*k+1) for k in range(n) ) 
% \end{Piton}
% \end{Verbatim}
% \endgroup
%
% \begingroup
% \PitonOptions{background-color=gray!10}
% \begin{Piton}
% def arctan(x,n=10):
%     if x < 0:
%         return -arctan(-x)##\footnote{First recursive call.}
%     elif x > 1: 
%         return pi/2 - arctan(1/x)##\footnote{Second recursive call.}
%     else: 
%         return sum( (-1)**k/(2*k+1)*x**(2*k+1) for k in range(n) ) 
% \end{Piton}
% \endgroup
%
%
% \vspace{1cm}
%
% If an environment |{Piton}| is used in an environment |{minipage}| of LaTeX,
% the notes are composed, of course, at the foot of the environment
% |{minipage}|. Recall that such |{minipage}| can't be broken by a page break.

%
% \begingroup
% \fvset{commandchars=\~\&\@,formatcom=\small\color{gray}}
% \begin{Verbatim}
% \PitonOptions{background-color=gray!10}
% \emphase\begin{minipage}{\linewidth}
% \begin{Piton}
% def arctan(x,n=10):
%     if x < 0:
%         return -arctan(-x)~emphase&##\footnote{First recursive call.}@
%     elif x > 1: 
%         return pi/2 - arctan(1/x)~emphase&##\footnote{Second recursive call.}@
%     else: 
%         return sum( (-1)**k/(2*k+1)*x**(2*k+1) for k in range(n) ) 
% \end{Piton}
% \end{minipage}
% \end{Verbatim}
% \endgroup
%
% \begingroup
% \PitonOptions{background-color=gray!10}
% \begin{minipage}{\linewidth}
% \begin{Piton}
% def arctan(x,n=10):
%     if x < 0:
%         return -arctan(-x)##\footnote{First recursive call.}
%     elif x > 1: 
%         return pi/2 - arctan(1/x)##\footnote{Second recursive call.}
%     else: 
%         return sum( (-1)**k/(2*k+1)*x**(2*k+1) for k in range(n) ) 
% \end{Piton}
% \end{minipage}
% \endgroup
%
%
% \vspace{1cm}
% If one embed an environment |{Piton}| in an environment |{minipage}|
% (typically in order to limit the width of a colored background), it's
% necessary to embed the whole environment |{minipage}| in an environment
% |{savenotes}| (of \pkg{footnote} or \pkg{footnotehyper}) in order to have the
% footnotes composed at the bottom of the page. 
%
% \begingroup
% \fvset{commandchars=\~\&\@,formatcom=\small\color{gray}}
% \begin{Verbatim}
% \PitonOptions{background-color=gray!10}
% ~emphase&\begin{savenotes}@
% \begin{minipage}{13cm}
% \begin{Piton}
% def arctan(x,n=10):
%     if x < 0:
%         return -arctan(-x)~emphase&##\footnote{First recursive call.}@
%     elif x > 1: 
%         return pi/2 - arctan(1/x)~emphase&##\footnote{Second recursive call.}@
%     else: 
%         return sum( (-1)**k/(2*k+1)*x**(2*k+1) for k in range(n) ) 
% \end{Piton}
% \end{minipage}
% ~emphase&\end{savenotes}@
% \end{Verbatim}
% \endgroup
%
%
%
% \begin{savenotes}
% \PitonOptions{background-color=gray!10}
% \begin{minipage}{13cm}
% \begin{Piton}
% def arctan(x,n=10):
%     if x < 0:
%         return -arctan(-x)##\footnote{First recursive call.}
%     elif x > 1: 
%         return pi/2 - arctan(1/x)##\footnote{Second recursive call.}
%     else: 
%         return sum( (-1)**k/(2*k+1)*x**(2*k+1) for k in range(n) ) 
% \end{Piton}
% \end{minipage}
% \end{savenotes}
%
%
% \subsection{An example of tuning of the styles}
%
% The graphical styles have been presented in the section \ref{styles},
% p.~\pageref{styles}.
%
% \smallskip
% We present now an example of tuning of these styles adapted to the documents
% in black and white. We use the font \emph{DejaVu Sans Mono}\footnote{See:
% \url{https://dejavu-fonts.github.io}} specified by the command |\setmonofont| of 
% \pkg{fontspec}. 
%
%
% \begin{Verbatim}
% \setmonofont[Scale=0.85]{DejaVu Sans Mono}
%
% \SetPitonStyle
%   {
%     Number = ,
%     String = \itshape , 
%     String.Doc = \color{gray} \slshape ,
%     Operator = , 
%     Operator.Word = \bfseries ,
%     Name.Builtin = ,
%     Name.Function = \bfseries \colorbox{gray!20} ,
%     Comment = \color{gray} ,
%     Comment.LaTeX = \color{gray},
%     Keyword = \bfseries ,
%     Name.Namespace = ,
%     Name.Class = , 
%     Name.Type = ,
%     InitialValues = \color{gray}
%   }
% \end{Verbatim}
%
%
% \begingroup
%
% \setmonofont[Scale=0.85]{DejaVu Sans Mono}
%
% \PitonOptions{splittable}
%
% \SetPitonStyle
%   {
%     Number = ,
%     String = \itshape , 
%     String.Doc = \color{gray} \slshape ,
%     Operator = , 
%     Operator.Word = \bfseries ,
%     Name.Builtin = ,
%     Name.Function = \bfseries \colorbox{gray!20} ,
%     Comment = \color{gray} ,
%     Comment.LaTeX = \color{gray} ,
%     Keyword = \bfseries ,
%     Name.Namespace = ,
%     Name.Class = , 
%     Name.Type = ,
%     InitialValues = \color{gray}
%   }
%
%
% \bigskip
%
% \begin{Piton}
% from math import pi
%
% def arctan(x,n=10):
%     '''Compute the value of arctan(x)
%        n is the number of terms if the sum'''
%     if x < 0:
%         return -arctan(-x) # appel récursif
%     elif x > 1: 
%         return pi/2 - arctan(1/x) 
%         ## (we have used that $\arctan(x)+\arctan(1/x)=\pi/2$ for $x>0$)
%     else: 
%         s = 0
%         for k in range(n):
%             s += (-1)**k/(2*k+1)*x**(2*k+1)
%         return s 
% \end{Piton}
%
% \endgroup
% 
%
% \bigskip
% The previous example has been composed while the key |splittable| (of
% |\PitonOptions|) is in force. That's why a page break may have occurred.
% \clearpage
%
% \section{Implementation}
%
%     \begin{macrocode}
\NeedsTeXFormat{LaTeX2e}
\RequirePackage{l3keys2e}
\ProvidesExplPackage
  {piton}
  {\myfiledate}
  {\myfileversion}
  {Highlight Python codes with LPEG on LuaLaTeX}
%    \end{macrocode}
%
% \bigskip
%    \begin{macrocode}
\msg_new:nnn { piton } { LuaLaTeX~mandatory }
  { The~package~'piton'~must~be~used~with~LuaLaTeX.\\ It~won't~be~loaded. }
\sys_if_engine_luatex:F { \msg_critical:nn { piton } { LuaLaTeX~mandatory } }
%    \end{macrocode}
% 
% \bigskip
%    \begin{macrocode}
\RequirePackage { luatexbase } 
%    \end{macrocode}
%
% \bigskip
% The boolean |\c_@@_footnotehyper_bool| will indicate if the option
% |footnotehyper| is used.
%    \begin{macrocode}
\bool_new:N \c_@@_footnotehyper_bool
%    \end{macrocode}
%
% \medskip
% The boolean |\c_@@_footnote_bool| will indicate if the option |footnote| is
% used, but quicky, it will also be set to |true| if the option |footnotehyper|
% is used.
%    \begin{macrocode}
\bool_new:N \c_@@_footnote_bool
%    \end{macrocode}
% 
% \bigskip
% We define a set of keys for the options at load-time.
%    \begin{macrocode}
\keys_define:nn { piton / package }
  { 
    footnote .bool_set:N = \c_@@_footnote_bool ,
    footnotehyper .bool_set:N = \c_@@_footnotehyper_bool ,
    escape-inside .tl_set:N = \c_@@_escape_inside_tl ,
    escape-inside .initial:n = , 
    unknown .code:n = \msg_error:nn { piton } { unknown~key~for~package }
  }
%    \end{macrocode}
%
%    \begin{macrocode}
\msg_new:nnn { piton } { unknown~key~for~package }
  {
    Unknown~key.\\
    You~have~used~the~key~'\l_keys_key_str'~but~the~only~keys~available~here~
    are~'escape-inside',~'footnote'~and~'footnotehyper'.~Other~keys~are~
    available~in~\token_to_str:N \PitonOptions.\\
    That~key~will~be~ignored.
  }
%    \end{macrocode}
% 
% \bigskip
% We process the options provided by the user at load-time.
%    \begin{macrocode}
\ProcessKeysOptions { piton / package }
%    \end{macrocode}
%
% \bigskip
%    \begin{macrocode}
\begingroup
\cs_new_protected:Npn \@@_set_escape_char:nn #1 #2 
  {
    \lua_now:n { begin_escape = "#1" }
    \lua_now:n { end_escape = "#2" }
  }
\cs_generate_variant:Nn \@@_set_escape_char:nn { x x }
\@@_set_escape_char:xx 
  { \tl_head:V \c_@@_escape_inside_tl }
  { \tl_tail:V \c_@@_escape_inside_tl }
\endgroup
%    \end{macrocode}
% 
% 
% \bigskip
%    \begin{macrocode}
\hook_gput_code:nnn { begindocument } { . }
  {
    \@ifpackageloaded { xcolor }
      { }
      { \msg_fatal:nn { piton } { xcolor~not~loaded } }
  }
%    \end{macrocode}
%
%    \begin{macrocode}     
\msg_new:nnn { piton } { xcolor~not~loaded }
  {
    xcolor~not~loaded \\
    The~package~'xcolor'~is~required~by~'piton'.\\
    This~error~is~fatal.
  }
%    \end{macrocode}
% 
%
%    \begin{macrocode}
\msg_new:nnn { piton } { footnote~with~footnotehyper~package }
  { 
    Footnote~forbidden.\\
    You~can't~use~the~option~'footnote'~because~the~package~
    footnotehyper~has~already~been~loaded.~
    If~you~want,~you~can~use~the~option~'footnotehyper'~and~the~footnotes~  
    within~the~environments~of~piton~will~be~extracted~with~the~tools~
    of~the~package~footnotehyper.\\
    If~you~go~on,~the~package~footnote~won't~be~loaded.
  }
%    \end{macrocode}
%
%    \begin{macrocode}
\msg_new:nnn { piton } { footnotehyper~with~footnote~package }
  { 
    You~can't~use~the~option~'footnotehyper'~because~the~package~
    footnote~has~already~been~loaded.~
    If~you~want,~you~can~use~the~option~'footnote'~and~the~footnotes~  
    within~the~environments~of~piton~will~be~extracted~with~the~tools~
    of~the~package~footnote.\\ 
    If~you~go~on,~the~package~footnotehyper~won't~be~loaded.
  }
%    \end{macrocode}
%
% \medskip
%    \begin{macrocode}
\bool_if:NT \c_@@_footnote_bool 
  { 
%    \end{macrocode}
% The class \cls{beamer} has its own system to extract footnotes and that's why
% we have nothing to do if \cls{beamer} is used. 
%    \begin{macrocode}
    \@ifclassloaded { beamer }
      { \bool_set_false:N \c_@@_footnote_bool }
      { 
        \@ifpackageloaded { footnotehyper }
          { \@@_error:n { footnote~with~footnotehyper~package } }
          { \usepackage { footnote } }
      }
  }
%    \end{macrocode}
%
%    \begin{macrocode}
\bool_if:NT \c_@@_footnotehyper_bool 
  { 
%    \end{macrocode}
% The class \cls{beamer} has its own system to extract footnotes and that's why
% we have nothing to do if \cls{beamer} is used. 
%    \begin{macrocode}
    \@ifclassloaded { beamer }
      { \bool_set_false:N \c_@@_footnote_bool }
      { 
        \@ifpackageloaded { footnote }
          { \@@_error:n { footnotehyper~with~footnote~package } }
          { \usepackage { footnotehyper } }
        \bool_set_true:N \c_@@_footnote_bool 
      }
  }
%    \end{macrocode}
% The flag |\c_@@_footnote_bool| is raised and so, we will only have to test
% |\c_@@_footnote_bool| in order to know if we have to insert an environment
% |{savenotes}|.
% 
% \medskip
% \subsection{Parameters}
%
% The following token list will contains the (potential) informations to write
% on the |aux| (to be used in the next compilation).
%    \begin{macrocode}
\tl_new:N \g_@@_aux_tl
%    \end{macrocode}
% 
% \medskip
% The following flag corresponds to the key |splittable| of |\PitonOptions|.
%    \begin{macrocode}
\bool_new:N \l_@@_splittable_bool
%    \end{macrocode}
%
% \medskip
% The following string corresponds to the key |background-color| of |\PitonOptions|.
%    \begin{macrocode}
\str_new:N \l_@@_background_color_str
%    \end{macrocode}
%
% \medskip
% We will compute the maximal width of the lines of an environment |{Piton}| in
% |\l_@@_width_dim|.
%    \begin{macrocode}
\dim_new:N \l_@@_width_dim 
%    \end{macrocode}
% The value of that dimension as written on the |aux| file will be stored in 
% |\l_@@_width_on_aux_dim|.
%    \begin{macrocode}
\dim_new:N \l_@@_width_on_aux_dim 
%    \end{macrocode}
%
% \medskip
% We will count the environments |{Piton}| (and, in fact, also the commands
% |\PitonInputFile|, despite the name |\g_@@_env_int|).
%    \begin{macrocode}
\int_new:N \g_@@_env_int 
%    \end{macrocode}
% 
% \medskip
% The following boolean corresponds to the key |slim| of |\PitonOptions|.
%    \begin{macrocode}
\bool_new:N \l_@@_slim_bool
%    \end{macrocode}
%
% \medskip
% The following dimension corresponds to the key |left-margin| of |\PitonOptions|.
%    \begin{macrocode}
\dim_new:N \l_@@_left_margin_dim
%    \end{macrocode}
% 
% \subsection{The gobbling mechanism}
%
% \medskip
% The following integer is the number of characters to gobble on the left side
% of the Python listings. Of course, the initial value is $0$.
%    \begin{macrocode}
\int_new:N \l_@@_gobble_int 
%    \end{macrocode}
%
% \medskip
%    \begin{macrocode}
\cs_new_protected:Npn \@@_define_gobble_syntax:n #1
  { \lua_now:n { define_gobble_syntax(#1) } }
%    \end{macrocode}
%
% \medskip
% \subsection{Treatment of a line of code}
% 
% In the contents provided by Lua, each line of the Python code will be
% surrounded by |\@@_begin_line:| and |\@@_end_line:|. 
%
%    \begin{macrocode}
\cs_set_protected:Npn \@@_begin_line: #1 \@@_end_line:
  { 
    \bool_lazy_and:nnT \l_@@_splittable_bool \c_@@_footnote_bool
      { \begin { savenotes } } 
%    \end{macrocode}
%
% Be careful: there is curryfication in the following lines.
%    \begin{macrocode}
    \bool_if:NTF \l_@@_slim_bool
      { \hbox_set:Nn \l_tmpa_box }
      { 
        \str_if_empty:NTF \l_@@_background_color_str
          { \hbox_set_to_wd:Nnn \l_tmpa_box \linewidth }
          { 
            \hbox_set_to_wd:Nnn \l_tmpa_box 
              { \dim_eval:n { \linewidth - 0.5 em } }
          }
      }
      { 
        \skip_horizontal:N \l_@@_left_margin_dim
        \bool_if:NT \l_@@_line_numbers_bool
          {
            \bool_if:NF \l_@@_all_line_numbers_bool
              { \tl_if_empty:nF { #1 } }
              \@@_print_number:
          }
        \strut 
        \str_if_empty:NF \l_@@_background_color_str \space 
        #1 \hfil 
      } 
%    \end{macrocode}
% We compute in |\l_@@_width_dim| the maximal width of the lines of the
% environments. 
%    \begin{macrocode}
    \dim_compare:nNnT { \box_wd:N \l_tmpa_box } > \l_@@_width_dim 
      { \dim_set:Nn \l_@@_width_dim { \box_wd:N \l_tmpa_box } }
    \box_set_dp:Nn \l_tmpa_box { \box_dp:N \l_tmpa_box + 1.25 pt } 
    \box_set_ht:Nn \l_tmpa_box { \box_ht:N \l_tmpa_box + 1.25 pt } 
    \tl_if_empty:NTF \l_@@_background_color_str
      { \box_use_drop:N \l_tmpa_box }
      {
        \vbox_top:n 
          { 
            \hbox:n
              { 
                \exp_args:NV \color \l_@@_background_color_str
                \vrule height \box_ht:N \l_tmpa_box 
                       depth \box_dp:N \l_tmpa_box 
                       width \l_@@_width_on_aux_dim
              } 
            \skip_vertical:n { - \box_ht_plus_dp:N \l_tmpa_box }
            \box_set_wd:Nn \l_tmpa_box \l_@@_width_on_aux_dim 
            \box_use_drop:N \l_tmpa_box
          }
      }   
    \bool_lazy_and:nnT \l_@@_splittable_bool \c_@@_footnote_bool
      { \end { savenotes } }
    \vspace { - 2.5 pt }
  }
%    \end{macrocode}
%
% 
% \medskip
% \subsection{PitonOptions}
%
% \medskip
% The following parameters correspond to the keys |line-numbers| and
% |all-line-numbers|.
%    \begin{macrocode}
\bool_new:N \l_@@_line_numbers_bool 
\bool_new:N \l_@@_all_line_numbers_bool 
%    \end{macrocode}
% 
% \medskip
% The following flag corresponds to the key |resume|.
%    \begin{macrocode}
\bool_new:N \l_@@_resume_bool 
%    \end{macrocode}
% 
% \bigskip
% Be careful! The name of the following set of keys must be considered as
% public! Hence, it should \emph{not} be changed.
% 
%    \begin{macrocode}
\keys_define:nn { PitonOptions }
  {
    gobble           .int_set:N         = \l_@@_gobble_int , 
    gobble           .value_required:n  = true ,
    auto-gobble      .code:n            = \int_set:Nn \l_@@_gobble_int { -1 } , 
    auto-gobble      .value_forbidden:n = true ,
    env-gobble       .code:n            = \int_set:Nn \l_@@_gobble_int { -2 } , 
    env-gobble       .value_forbidden:n = true ,
    line-numbers     .bool_set:N        = \l_@@_line_numbers_bool ,
    line-numbers     .default:n         = true ,
    all-line-numbers .code:n = 
      \bool_set_true:N \l_@@_line_numbers_bool 
      \bool_set_true:N \l_@@_all_line_numbers_bool ,
    all-line-numbers .value_forbidden:n = true  ,
    resume           .bool_set:N        = \l_@@_resume_bool ,
    resume           .value_forbidden:n = true ,
    splittable       .bool_set:N        = \l_@@_splittable_bool ,
    splittable       .default:n         = true , 
    background-color .str_set:N         = \l_@@_background_color_str ,
    background-color .value_required:n  = true ,
    slim             .bool_set:N        = \l_@@_slim_bool ,
    slim             .default:n         = true ,
    left-margin      .dim_set:N         = \l_@@_left_margin_dim ,
    left-margin      .value_required:n  = true ,
    unknown          .code:n = 
      \msg_error:nn { piton } { Unknown~key~for~PitonOptions }
  }
%    \end{macrocode}
%
%  \bigskip
%    \begin{macrocode}
\msg_new:nnn { piton } { Unknown~key~for~PitonOptions }
  { 
    Unknown~key. \\
    The~key~'\l_keys_key_str'~is~unknown~for~\token_to_str:N \PitonOptions.~The~
    available~keys~are:~all-line-numbers,~auto-gobble,~env-gobble,~gobble,~
    left-margin,~line-numbers,~resume,~slim~and~splittable.\\
    If~you~go~on,~that~key~will~be~ignored.
  }
%    \end{macrocode}
% 
% \bigskip
% The argument of |\PitonOptions| is provided by curryfication.
%    \begin{macrocode}
\NewDocumentCommand \PitonOptions { } { \keys_set:nn { PitonOptions } }
%    \end{macrocode}
%
% \medskip
% \subsection{The numbers of the lines}
%
% \medskip
% The following counter will be used to count the lines in the code when the
% user requires the numbers of the lines to be printed.
%    \begin{macrocode}
\int_new:N \g_@@_line_int 
%    \end{macrocode}
% 
% 
%    \begin{macrocode}
\cs_new_protected:Npn \@@_print_number:
  {
    \int_gincr:N \g_@@_line_int 
    \hbox_overlap_left:n
      { 
        { \color { gray } \footnotesize \int_to_arabic:n \g_@@_line_int }
        \skip_horizontal:n { 0.4 em } 
      }
  }
%    \end{macrocode}
% 
%
% \medskip
% \subsection{The command to write on the aux file}
%
%   
%    \begin{macrocode}
\cs_new_protected:Npn \@@_write_aux:
  {
    \tl_if_empty:NF \g_@@_aux_tl 
      {
        \iow_now:Nn \@mainaux { \ExplSyntaxOn }
        \iow_now:Nx \@mainaux 
          {
            \tl_gset:cn { c_@@_ \int_use:N \g_@@_env_int _ tl } 
              { \exp_not:V \g_@@_aux_tl } 
          }
        \iow_now:Nn \@mainaux { \ExplSyntaxOff }
      }
    \tl_gclear:N \g_@@_aux_tl 
  }
%    \end{macrocode}
%
%    \begin{macrocode}
\cs_new_protected:Npn \@@_width_to_aux:
  {
    \bool_if:NT \l_@@_slim_bool
      {
        \str_if_empty:NF \l_@@_background_color_str
          {
            \tl_gput_right:Nx \g_@@_aux_tl
              {
                \dim_set:Nn \l_@@_width_on_aux_dim 
                  { \dim_use:N \l_@@_width_dim + 0.5 em }
              }
          }
      }
  }
%    \end{macrocode}
% 
% \medskip
% \subsection{The main commands and environments for the final user}
% 
%    \begin{macrocode}
\NewDocumentCommand { \piton } { v }
  {
    \group_begin:
      \ttfamily
      \cs_set_protected:Npn \@@_begin_line: { }
      \cs_set_protected:Npn \@@_end_line: { }
      \lua_now:n { Parse(token.scan_argument()) } { #1 }
    \group_end:
  }
%    \end{macrocode}
%
% \medskip
% The command |\@@_piton:n| does \emph{not} take in its argument verbatim.
%    \begin{macrocode}
\cs_new_protected:Npn \@@_piton:n #1
  { 
    \group_begin:
      \cs_set_protected:Npn \@@_begin_line: { }
      \cs_set_protected:Npn \@@_end_line: { }
      \lua_now:e { Parse(token.scan_argument()) } { #1 }
    \group_end:
  }
%    \end{macrocode}
% 
% 
% \bigskip
%    \begin{macrocode}
\NewDocumentCommand { \PitonInputFile } { m }
  {
    \int_gincr:N \g_@@_env_int 
    \tl_gclear:N \g_@@_aux_tl
    \tl_if_exist:cT { c_@@ _ \int_use:N \g_@@_env_int _ tl }
      { \use:c { c_@@ _ \int_use:N \g_@@_env_int _ tl } }
    \bool_if:NF \l_@@_splittable_bool
      { \bool_if:NT \c_@@_footnote_bool { \begin { savenotes } } }
    \dim_compare:nNnT \l_@@_width_on_aux_dim = \c_zero_dim
      { \dim_set_eq:NN \l_@@_width_on_aux_dim \linewidth }
    \bool_if:NF \l_@@_resume_bool { \int_gzero:N \g_@@_line_int }
    \group_begin:
      \dim_set_eq:NN \parindent \c_zero_dim 
      \ttfamily
      \lua_now:e { ParseFile(token.scan_argument()) } { #1 }
    \@@_width_to_aux:
    \group_end:
    \@@_write_aux:
    \bool_if:NF \l_@@_splittable_bool
      { \bool_if:NT \c_@@_footnote_bool { \end { savenotes } } }
  }
%    \end{macrocode}
%
% 
% \bigskip 
%    \begin{macrocode}
\NewDocumentCommand { \NewPitonEnvironment } { m m m m }
  { 
    \dim_zero:N \parindent 
%    \end{macrocode}
% We construct a TeX macro which will catch as argument all the tokens until
% |\end{|\texttt{\textsl{name_env}}|}| with, in that
% |\end{|\texttt{\textsl{name_env}}|}|, the catcodes of |\|, |{| and |}| equal to
% 12 (``\texttt{other}''). The latter explains why the definition of that
% function is a bit complicated.
%    \begin{macrocode}
    \use:x 
      { 
        \cs_set_protected:Npn 
          \use:c { _@@_collect_ #1 :w } 
          ####1 
          \c_backslash_str end \c_left_brace_str #1 \c_right_brace_str
      }
          {
            \group_end:
            \mode_if_vertical:TF 
              { \mode_leave_vertical: } 
              \newline 
%    \end{macrocode}
% Be careful: there is curryfication in the following code.
%    \begin{macrocode}
            \bool_if:NF \l_@@_splittable_bool 
              { 
                \bool_if:NT \c_@@_footnote_bool { \begin { savenotes } } 
                \vbox_top:n 
              }
              {
                \ttfamily
                \dim_zero:N \lineskip 
                \int_case:nnF \l_@@_gobble_int 
                  { 
                    0 
%    \end{macrocode}
% Be careful: the last argument is provided by curryfication.
%    \begin{macrocode}
                    { \lua_now:n { Parse(token.scan_argument()) } }
                    { -1 }
                    { \lua_now:n { AutoGobbleParse(token.scan_argument()) } } 
                    { -2 }
                    { \lua_now:n { EnvGobbleParse(token.scan_argument()) } } 
                  }
                  {
                     \exp_args:NV \@@_define_gobble_syntax:n \l_@@_gobble_int 
                     \lua_now:n { GobbleParse(token.scan_argument()) } 
                  }
                { ##1 }
                \vspace { 2.5 pt } 
                \@@_width_to_aux:
              }
            \bool_if:NF \l_@@_splittable_bool
              { \bool_if:NT \c_@@_footnote_bool { \end { savenotes } } }
%    \end{macrocode}
% The following |\end{#1}| is only for the groups and the stack of
% environments of LaTeX.
%    \begin{macrocode}
            \end { #1 }
            \@@_write_aux:
          }   
%    \end{macrocode}
% 
% 
% \bigskip
% We can now define the new environment.
%
% We are still in the definition of the command |\NewPitonEnvironment|...
%    \begin{macrocode}
    \NewDocumentEnvironment { #1 } { #2 } 
      {
        #3 
        \int_gincr:N \g_@@_env_int 
        \tl_gclear:N \g_@@_aux_tl
        \tl_if_exist:cT { c_@@ _ \int_use:N \g_@@_env_int _ tl }
          { \use:c { c_@@ _ \int_use:N \g_@@_env_int _ tl } }
        \dim_compare:nNnT \l_@@_width_on_aux_dim = \c_zero_dim
          { \dim_set_eq:NN \l_@@_width_on_aux_dim \linewidth }
        \bool_if:NF \l_@@_resume_bool { \int_gzero:N \g_@@_line_int }
        \group_begin:
        \box_clear:N \l_tmpa_box
        \tl_map_function:nN 
          { \ \\ \{ \} \$ \& \# \^ \_ \% \~ } 
          \char_set_catcode_other:N 
        \use:c { _@@_collect_ #1 :w }
      }
      { #4 }
%    \end{macrocode}
%
% \medskip
% The following code is for technical reasons. We want to change the catcode of
% |^^M| before catching the arguments of the new environment we are defining.
% Indeed, if not, we will have problems if there is a final optional argument in
% our environment (if that final argument is not used by the user in an
% instance of the environment, a spurious space is inserted, probably because
% the |^^M| is converted to space).
%    \begin{macrocode}
    \AddToHook { env / #1 / begin } { \char_set_catcode_other:N \^^M }
  }
%    \end{macrocode}
% This is the end of the definition of the command |\NewPitonEnvironment|.
%
% \bigskip
%    \begin{macrocode}
\NewPitonEnvironment { Piton } { } { } { }
%    \end{macrocode}
%
% \bigskip
% \subsection{The styles}
% 
% \medskip
% The following command is fundamental: it will be used by the Lua code.
%    \begin{macrocode}
\NewDocumentCommand { \PitonStyle } { m } { \use:c { pitonStyle #1 } }
%    \end{macrocode}
%
% \medskip
% The following command takes in its argument by curryfication.
%    \begin{macrocode}
\NewDocumentCommand { \SetPitonStyle } { } { \keys_set:nn { piton / Styles } } 
%    \end{macrocode}
% 
% \medskip
%    \begin{macrocode}
\cs_new_protected:Npn \@@_math_scantokens:n #1 
  { \normalfont \scantextokens { $#1$ } }
%    \end{macrocode}
% 
% \medskip
%    \begin{macrocode}
\keys_define:nn { piton / Styles }
  {
    String.Interpol  .tl_set:c = pitonStyle String.Interpol , 
    String.Interpol  .value_required:n = true ,
    FormattingType   .tl_set:c = pitonStyle FormattingType ,
    FormattingType   .value_required:n = true ,
    Dict.Value       .tl_set:c = pitonStyle Dict.Value ,
    Dict.Value       .value_required:n = true ,
    Name.Decorator   .tl_set:c = pitonStyle Name.Decorator ,
    Name.Decorator   .value_required:n = true ,
    Name.Function    .tl_set:c = pitonStyle Name.Function ,
    Name.Function    .value_required:n = true ,
    Keyword          .tl_set:c = pitonStyle Keyword ,
    Keyword          .value_required:n = true ,
    Keyword.Constant .tl_set:c = pitonStyle Keyword.Constant ,
    Keyword.constant .value_required:n = true ,
    String.Doc       .tl_set:c = pitonStyle String.Doc ,
    String.Doc       .value_required:n = true ,
    Interpol.Inside  .tl_set:c = pitonStyle Interpol.Inside ,
    Interpol.Inside  .value_required:n = true ,
    String.Long      .tl_set:c = pitonStyle String.Long ,
    String.Long      .value_required:n = true ,
    String.Short     .tl_set:c = pitonStyle String.Short ,
    String.Short     .value_required:n = true ,
    String           .meta:n = { String.Long = #1 , String.Short = #1 } ,
    Comment.Math     .tl_set:c = pitonStyle Comment.Math , 
    Comment.Math     .default:n = \@@_math_scantokens:n ,
    Comment.Math     .initial:n = ,
    Comment          .tl_set:c = pitonStyle Comment , 
    Comment          .value_required:n = true ,
    InitialValues    .tl_set:c = pitonStyle InitialValues ,
    InitialValues    .value_required:n = true ,
    Number           .tl_set:c = pitonStyle Number , 
    Number           .value_required:n = true ,
    Name.Namespace   .tl_set:c = pitonStyle Name.Namespace , 
    Name.Namespace   .value_required:n = true ,
    Name.Class       .tl_set:c = pitonStyle Name.Class , 
    Name.Class       .value_required:n = true ,
    Name.Builtin     .tl_set:c = pitonStyle Name.Builtin , 
    Name.Builtin     .value_required:n = true ,
    Name.Type        .tl_set:c = pitonStyle Name.Type , 
    Name.Type        .value_required:n = true ,
    Operator         .tl_set:c = pitonStyle Operator , 
    Operator         .value_required:n = true ,
    Operator.Word    .tl_set:c = pitonStyle Operator.Word , 
    Operator.Word    .value_required:n = true ,
    Post.Function    .tl_set:c = pitonStyle Post.Function , 
    Post.Function    .value_required:n = true ,
    Exception        .tl_set:c = pitonStyle Exception ,
    Exception        .value_required:n = true ,
    Comment.LaTeX    .tl_set:c = pitonStyle Comment.LaTeX ,
    Comment.LaTeX    .value_required:n = true ,
    unknown          .code:n = 
      \msg_error:nn { piton } { Unknown~key~for~SetPitonStyle }
  }
%    \end{macrocode}
% 
% 
% \bigskip
%    \begin{macrocode}
\msg_new:nnn { piton } { Unknown~key~for~SetPitonStyle } 
  {
    The~style~'\l_keys_key_str'~is~unknown.\\
    This~key~will~be~ignored.\\
    The~available~styles~are~(in~alphabetic~order):~
    Comment,~
    Comment.LaTeX,~
    Dict.Value,~
    Exception,~
    InitialValues,~ 
    Keyword,~
    Keyword.Constant,~
    Name.Builtin,~
    Name.Class,~
    Name.Decorator,~
    Name.Function,~
    Name.Namespace,~
    Number,~
    Operator,~
    Operator.Word,~
    String,~
    String.Doc,~
    String.Long,~
    String.Short,~and~
    String.Interpol. 
  }
%    \end{macrocode}
%
% 
% \subsection{The initial style}
%
% The initial style is inspired by the style ``manni'' of Pygments.
% 
% \medskip
%    \begin{macrocode}
\SetPitonStyle
  {                                                       
    Comment          = \color[HTML]{0099FF} \itshape , 
    Exception        = \color[HTML]{CC0000} ,
    Keyword          = \color[HTML]{006699} \bfseries ,               
    Keyword.Constant = \color[HTML]{006699} \bfseries ,               
    Name.Builtin     = \color[HTML]{336666} ,
    Name.Decorator   = \color[HTML]{9999FF}, 
    Name.Class       = \color[HTML]{00AA88} \bfseries ,
    Name.Function    = \color[HTML]{CC00FF} , 
    Name.Namespace   = \color[HTML]{00CCFF} , 
    Number           = \color[HTML]{FF6600} ,
    Operator         = \color[HTML]{555555} ,
    Operator.Word    = \bfseries ,
    String           = \color[HTML]{CC3300} ,         
    String.Doc       = \color[HTML]{CC3300} \itshape , 
    String.Interpol  = \color[HTML]{AA0000} ,
    Comment.LaTeX    = \normalfont \color[rgb]{.468,.532,.6} , 
    Name.Type        = \color[HTML]{336666} ,
    InitialValues    = \@@_piton:n ,
    Dict.Value       = \@@_piton:n ,
    Post.Function    = \@@_piton:n ,
    Interpol.Inside  = \color{black}\@@_piton:n ,
  }
%    \end{macrocode}
%
% \subsection{Security}
%
%     \begin{macrocode}
\AddToHook { env / piton / begin } 
   { \msg_fatal:nn { piton } { No~environment~piton } }

\msg_new:nnn { piton } { No~environment~piton }
  { 
    There~is~no~environment~piton!\\
    There~is~an~environment~{Piton}~and~a~command~
    \token_to_str:N \piton\ but~there~is~no~environment~
    {piton}.~This~error~is~fatal.
  }
%    \end{macrocode}
% 
%
% \bigskip
% \subsection{The Lua code}
%
% \medskip
%    \begin{macrocode}
\ExplSyntaxOff
\RequirePackage{luacode}
%    \end{macrocode}
%   
% \vspace{1cm}
%    \begin{macrocode}
\begin{luacode*}
local P, S, V , C , Ct, Cc, Cf = lpeg.P, lpeg.S, lpeg.V, lpeg.C, lpeg.Ct, lpeg.Cc, lpeg.Cf


--[[ By convention, a capture which provides as value a table (and not a string), provides, in fact,
a string (the first element of the table) which is a formatting LaTeX instruction (it will be
thrown back to TeX with normal catcodes (ant not ``other'' catcode for everybody).]]

local function L(string)
  return Cc ( { string } ) 
end 

local function K(pattern, style)
  return 
     L ( "{\\PitonStyle{" .. style .. "}{" )
     * C(pattern)
     * L ( "}}" )
end


--[[ The text in "escape" (between begin_escape and end_escape) is captured
and put in a table (with only one component). Indeed, we have decided that a capture
which is encapsulated in a table must be transmitted to TeX with the normal TeX catcodes.]]

local Escape = P(begin_escape)
               * Ct ( C ( ( 1 - P(end_escape) ) ^ 1 ) )
               * P(end_escape)


lpeg.locale(lpeg) -- mandatory

local alpha , digit , space , punct = lpeg.alpha , lpeg.digit , lpeg.space , lpeg.punct

-- Remember that à, â, ç, etc. are strings of length 2 (2 bytes)
local letter = alpha + P "_" 
 + P "â" + P "à" + P "ç" + P "é" + P "è" + P "ê" + P "ë" + P "ï" + P "î" + P "ô" + P "û" + P "ü" + 
     P "Â" + P "À" + P "Ç" + P "É" + P "È" + P "Ê" + P "Ë" + P "Ï" + P "Î" + P "Ô" + P "Û" + P "Ü" 

local alphanum = letter + digit

local identifier = letter * alphanum ^ 0

local Identifier = C ( identifier )

local Space = C ( ( space - P "\r" ) ^ 1 )

local SkipSpace = C ( ( space - P "\r" ) ^ 0 )

local Punct = C ( punct )


local EOL = ( P "\r" )
            *
            (
              ( space^0 * -1 )
              + 
              Cc (
                   { 
                     luatexbase.catcodetables.expl , 
                     '\\__piton_end_line: \\bool_if:NT \\l__piton_splittable_bool \\newline \\__piton_begin_line:'
                   } 
                 )
            ) 


local Number =
   K (
       ( digit^1 * P "." * digit^0 + digit^0 * P "." * digit^1 + digit^1 )
       * ( S "eE" * S "+-" ^ -1 * digit^1 ) ^ -1
       + digit^1 
       , 'Number' ) 


local Word = C ( ( ( 1 - space ) - S "'\"\r[()]" - digit ) ^ 1 )

if begin_escape ~= ''
then  Word = C ( ( ( 1 - space - P(begin_escape) - P(end_escape) ) - S "'\"\r[()]" - digit ) ^ 1 )
end

local Delim = C ( S "[()]" )


local Keyword = 
   K ( P "assert" + P "break" + P "case" + P "continue" + P "del"
       + P "elif" + P "else" + P "except" + P "exec" + P "finally" + P "for" + P "from" 
       + P "global" + P "if" + P "import" + P "lambda" + P "non local"
       + P "pass" + P "return" + P "try" + P "while"
       + P "with" + P "yield" + P "yield from" ,
   'Keyword' )
   + K ( P "True" + P "False" + P "None" , 'Keyword.Constant' ) 


local Builtin = 
   K ( P "__import__" + P "abs" + P "all" + P "any" + P "bin" + P "bool" + P "bytearray"
     + P "bytes" + P "chr" + P "classmethod" + P "compile" + P "complex" + P "delattr"
     + P "dict" + P "dir" + P "divmod" + P "enumerate" + P "eval" + P "filter"
     + P "float" + P "format" + P "frozenset" + P "getattr" + P "globals" + P "hasattr"
     + P "hash" + P "hex" + P "id" + P "input" + P "int" + P "isinstance" + P "issubclass"
     + P "iter" + P "len" + P "list" + P "locals" + P "map" + P "max" + P "memoryview" + P "min"
     + P "next" + P "object" + P "oct" + P "open" + P "ord" + P "pow" + P "print" + P "property"
     + P "range" + P "repr" + P "reversed" + P "round" + P "set" + P "setattr" + P "slice"
     + P "sorted" + P "staticmethod" + P "str" + P "sum" + P "super" + P "tuple" + P "type"
     + P "vars" + P "zip" ,
   'Name.Builtin' )


local Exception =
   K ( "ArithmeticError" + P "AssertionError" + P "AttributeError"
    + P "BaseException" + P "BufferError" + P "BytesWarning" + P "DeprecationWarning"
    + P "EOFError" + P "EnvironmentError" + P "Exception" + P "FloatingPointError"
    + P "FutureWarning" + P "GeneratorExit" + P "IOError" + P "ImportError"
    + P "ImportWarning" + P "IndentationError" + P "IndexError" + P "KeyError"
    + P "KeyboardInterrupt" + P "LookupError" + P "MemoryError" + P "NameError"
    + P "NotImplementedError" + P "OSError" + P "OverflowError"
    + P "PendingDeprecationWarning" + P "ReferenceError" + P "ResourceWarning"
    + P "RuntimeError" + P "RuntimeWarning" + P "StopIteration"
    + P "SyntaxError" + P "SyntaxWarning" + P "SystemError" + P "SystemExit"
    + P "TabError" + P "TypeError" + P "UnboundLocalError" + P "UnicodeDecodeError"
    + P "UnicodeEncodeError" + P "UnicodeError" + P "UnicodeTranslateError"
    + P "UnicodeWarning" + P "UserWarning" + P "ValueError" + P "VMSError"
    + P "Warning" + P "WindowsError" + P "ZeroDivisionError"
    + P "BlockingIOError" + P "ChildProcessError" + P "ConnectionError"
    + P "BrokenPipeError" + P "ConnectionAbortedError" + P "ConnectionRefusedError"
    + P "ConnectionResetError" + P "FileExistsError" + P "FileNotFoundError"
    + P "InterruptedError" + P "IsADirectoryError" + P "NotADirectoryError"
    + P "PermissionError" + P "ProcessLookupError" + P "TimeoutError"
    + P "StopAsyncIteration" + P "ModuleNotFoundError" + P "RecursionError" ,
   'Exception' )

local RaiseException = K ( P "raise" , 'Keyword' ) * SkipSpace * Exception * C ( P "(" ) 

local ExceptionInConsole = Exception *  C ( ( 1 - P "\r" ) ^ 0 ) * EOL  


local Namespace =
   K ( P "from" , 'Keyword' ) * Space * K ( alphanum^1 , 'Name.Namespace' )
   *  ( Space * K ( P "import" , 'Keyword' ) ) ^ -1


local ImportAs = K ( P "import" , 'Keyword' )
                  * Space
                  * K ( identifier , 'Name.Namespace' )
                  * ( SkipSpace * C ( P "," ) * SkipSpace * K ( identifier , 'Name.Namespace' ) ) ^ 0 
                  * (
                      Space * K ( P "as" , 'Keyword' ) * Space * K ( identifier , 'Name.Namespace' )
                    ) ^ 0 

local Class = K ( P "class" , 'Keyword' ) 
                * ( Space * K ( identifier , 'Name.Class' ) ) ^ -1 

local Decorator = K ( P "@" * letter^1 , 'Name.Decorator' ) 

local SingleShortInterpol =
    K ( P "{" , 'String.Interpol')
  * K ( ( 1 - S "}':" ) ^ 0 , 'Interpol.Inside' )
  * C ( P ":" * (1 - S "}:'") ^ 0 ) ^ -1
  * K ( P "}" , 'String.Interpol' )

local DoubleShortInterpol =
    K ( P "{" , 'String.Interpol' )
  * K ( ( 1 - S "}\":" ) ^ 0 , 'Interpol.Inside' )
  * ( K ( P ":" , 'String.Interpol' ) * C ( (1 - S "}:\"") ^ 0 ) ) ^ -1
  * K ( P "}" , 'String.Interpol' )

local SingleLongInterpol =
    K ( P "{" , 'String.Interpol' )
  * K ( ( 1 - S "}:\r" - P "'''" ) ^ 0 , 'Interpol.Inside' )
  * C ( P ":" * (1 - S "}:\r" - P "'''" ) ^ 0 ) ^ -1
  * K ( P "}" , 'String.Interpol' )

local DoubleLongInterpol =
    K ( P "{" , 'String.Interpol' )
  * K ( ( 1 - S "}:\r" - P "\"\"\"" ) ^ 0 , 'Interpol.Inside' )
  * C ( P ":" * (1 - S "}:\r" - P "\"\"\"" ) ^ 0 ) ^ -1
  * K ( P "}" , 'String.Interpol' )

local SingleShortPureString = C ( ( P "\\'" + P "{{" + P "}}" + 1 - S "{}'" ) ^ 1 )

local DoubleShortPureString = C ( ( P "\\\"" + P "{{" + P "}}" + 1 - S "{}\"" ) ^ 1 )

local SingleLongPureString = C ( ( 1 - P "'''" - S "{}'\r" ) ^ 1 )

local DoubleLongPureString = C ( ( 1 - P "\"\"\"" - S "{}\"\r" ) ^ 1 ) 

local SingleShortString =
    L ( "{\\PitonStyle{String.Short}{" )
     * (
           C ( P "f'" + P "F'" ) 
           * ( SingleShortInterpol + SingleShortPureString ) ^ 0 
           * C ( P "'" )
         + 
           C ( ( P "'" + P "r'" + P "R'" ) * ( P "\\'" + 1 - S "'\r" ) ^ 0 * P "'" )
       )
     * L ( "}}" ) 

local DoubleShortString =
    L ( "{\\PitonStyle{String.Short}{" )
     * (
           C ( P "f\"" + P "F\"" ) 
           * ( DoubleShortInterpol + DoubleShortPureString ) ^ 0 
           * C ( P "\"" )
         +
           C ( ( P "\"" + P "r\"" + P "R\"" ) * ( P "\\\"" + 1 - S "\"\r" ) ^ 0 * P "\"" )
       )
     * L ( "}}" ) 


local ShortString = SingleShortString + DoubleShortString


local SingleLongString =
      L "{\\PitonStyle{String.Long}{" 
       * (
             C ( S "fF" * P "'''" )
             * ( SingleLongInterpol + SingleLongPureString ) ^ 0
             * L "}}" 
             * (
                 EOL
                 + 
                 L "{\\PitonStyle{String.Long}{" 
                 * ( SingleLongInterpol + SingleLongPureString ) ^ 0
                 * L "}}"
                 * EOL
               ) ^ 0 
             * L "{\\PitonStyle{String.Long}{" 
             * ( SingleLongInterpol + SingleLongPureString ) ^ 0
           +
             C ( ( S "rR" ) ^ -1  * P "'''" * ( 1 - P "'''" - P "\r" ) ^ 0 ) 
             * L "}}" 
             * (
                 L "{\\PitonStyle{String.Long}{" 
                 * C ( ( 1 - P "'''" - P "\r" ) ^ 0 )
                 * L "}}" 
                 * EOL
               ) ^ 0 
             * L "{\\PitonStyle{String.Long}{" 
             * C ( ( 1 - P "'''" - P "\r" ) ^ 0 )
          )
       * C ( P "'''" )
       * L "}}" 


local DoubleLongString =
      L "{\\PitonStyle{String.Long}{" 
       * (
             C ( S "fF" * P "\"\"\"" )
             * ( DoubleLongInterpol + DoubleLongPureString ) ^ 0
             * L "}}" 
             * (
                 EOL
                 + 
                 L "{\\PitonStyle{String.Long}{" 
                 * ( DoubleLongInterpol + DoubleLongPureString ) ^ 0
                 * L "}}" 
                 * EOL
               ) ^ 0 
             * L "{\\PitonStyle{String.Long}{" 
             * ( DoubleLongInterpol + DoubleLongPureString ) ^ 0
           +
             C ( ( S "rR" ) ^ -1  * P "\"\"\"" * ( 1 - P "\"\"\"" - P "\r" ) ^ 0 ) 
             * L "}}" 
             * (
                 L "{\\PitonStyle{String.Long}{" 
                 * C ( ( 1 - P "\"\"\"" - P "\r" ) ^ 0 )
                 * L "}}" 
                 * EOL
               ) ^ 0 
             * L "{\\PitonStyle{String.Long}{" 
             * C ( ( 1 - P "\"\"\"" - P "\r" ) ^ 0 )
          )
       * C ( P "\"\"\"" )
       * L "}}" 



local LongString = SingleLongString + DoubleLongString


local Expression =
    P { "E" ,
         E = ( 1 - S "{}()[]\r," ) ^ 0
             *  (
                  (   P "{" * V "F" * P "}"
                    + P "(" * V "F" * P ")"
                    + P "[" * V "F" * P "]" ) * ( 1 - S "{}()[]\r," ) ^ 0
                ) ^ 0 ,
         F = ( 1 - S "{}()[]\r\"'" ) ^ 0
             * ( (
                     P "'" * (P "\\'" + 1 - S"'\r" )^0 * P "'"
                   + P "\"" * (P "\\\"" + 1 - S"\"\r" )^0 * P "\""
                   + P "{"  * V "F" * P "}"
                   + P "(" * V "F" * P ")"
                   + P "[" * V "F" * P "]"
                 ) * ( 1 - S "{}()[]\r\"'" ) ^ 0 ) ^ 0 , 
      }

local Param = SkipSpace * K ( identifier , '' ) * SkipSpace
                     *  ( K ( P "=" * Expression , 'InitialValues' )
                          +  K ( P ":" , '' ) * SkipSpace * K ( letter^1 , 'Name.Type' ))
                  + SkipSpace * K ( alphanum ^ 1 , '' ) * SkipSpace 

local Params =  Param * (  K ( P "," , '' ) * Param ) ^ 0

local StringDoc = K ( P "\"\"\"" , 'String.Doc' )
                      * ( K ( (1 - P "\"\"\"" - P "\r" ) ^ 0 , 'String.Doc' ) * EOL ) ^ 0
                      * K ( ( 1 - P "\"\"\"" - P "\r" ) ^ 0 * P "\"\"\"" , 'String.Doc' )
                  + K ( P "'''" , 'String.Doc' )
                      * ( K ( (1 - P "'''" - P "\r")^0 , 'String.Doc' ) * EOL ) ^ 0
                      * K ( ( 1 - P "'''" - P "\r")^0 * P "'''" , 'String.Doc' )

local CommentMath = P "$" * K ( ( 1 - S "$\r" ) ^ 1 , 'Comment.Math' ) * P "$"


local Comment = L ( "{\\PitonStyle{Comment}{" ) 
                * C ( P "#" ) * ( CommentMath + C ( ( 1 - S "$\r" ) ^ 1 ) ) ^ 0
                * L ( "}}" )
                * ( EOL + -1 )

local CommentLaTeX =
   P "##"
   * L "{\\PitonStyle{Comment.LaTeX}{\\ignorespaces" 
   * Ct ( C ( ( 1 - P "\r" ) ^ 0 ) ) 
   * L "}}" 
   * ( EOL + -1 ) 

local DefFunction =
   K ( P "def" , 'Keyword' )
   * ( Space
       * K ( identifier , 'Name.Function' ) 
       * ( SkipSpace * K ( P "(" , '' ) * Params * K ( P ")" , '' ) ) ^ -1
       * ( SkipSpace
            * K ( ( 1 - S ":\r" )^0 , 'Post.Function' ) 
            * K ( P ":" , 'Keyword' )
            * SkipSpace
            * ( EOL + CommentLaTeX + Comment )
            * SkipSpace
            * StringDoc ) ^ -1
      ) ^ -1 

local ItemDict = ShortString * SkipSpace * C ( P ":" ) * K ( Expression , 'Dict.Value' ) 

local ItemOfSet = SkipSpace * ( ItemDict + ShortString ) * SkipSpace 

local Set = C ( P "{" ) 
            * ItemOfSet * ( C ( P "," ) * ItemOfSet )  ^ 0 
            * C ( P "}" )

local Operator = K ( P "!=" + P "==" + P "<<" + P ">>" + S "-~+/*%=<>&.@|" , 'Operator')

local OperatorWord = K ( P "in" + P "is" + P "and" + P "or" + P "not" , 'Operator.Word')

local SyntaxPython =
      ( ( space - P "\r" ) ^0 * P "\r" ) ^ -1 * 
      (  ( space^1 * -1 ) 
         + EOL
         + Space
         + Escape 
         + CommentLaTeX
         + LongString 
         + Comment
         + ExceptionInConsole
         + Set 
         + Delim
         + Class * ( Space + Punct + EOL )
         + Namespace * ( Space + Punct + EOL )
         + ImportAs
         + RaiseException 
         + Keyword * ( Space + Punct + EOL )
         + DefFunction
         + ShortString
         + Decorator * ( Space + Punct + EOL )
         + Operator
         + OperatorWord * ( Space + Punct + EOL ) 
         + Builtin * ( Space + Punct + EOL )
         + Identifier 
         + Number
         + Word
      ) ^0 * -1 


local MinimalSyntax =
  P { "S" ;
      S = K ( (1 - P "\r" ) ^ 0 , '') + EOL * S
    }


function Parse(code)
  local t = Ct(SyntaxPython) : match(code)
  tex.sprint( luatexbase.catcodetables.expl , '\\__piton_begin_line:' )
  if t then else t = Ct(MinimalSyntax) : match(code) end   
  for i = 1 , #t do
    if type(t[i]) == 'string'
    then
      tex.sprint(luatexbase.catcodetables.CatcodeTableOther, t[i])
    else
      tex.tprint(t[i]) 
    end 
  end
  tex.sprint( luatexbase.catcodetables.expl , '\\__piton_end_line:' )
end

function ParseFile(name)
  s = ''
  for line in io.lines(name) do s = s .. '\r' .. line end
  Parse(s) 
end


function define_gobble_syntax(n) 
  GobbleSyntax = ( 1 - P "\r" ) ^ (-n)  * C ( ( 1 - P "\r" ) ^0 ) 
               * ( C ( P "\r" )
                   * ( 1 - P "\r" ) ^ (-n)
                   * C ( ( 1 - P "\r" ) ^0 )
                 ) ^ 0
end 

function GobbleParse(code)
  local t = Ct(GobbleSyntax):match(code)
  local new_code = ""
  for i = 1 , #t do
    new_code = new_code .. t[i]
  end
  Parse(new_code)
end

function add(acc,new_value)
  return acc + new_value
end 




--[[ The following LPEG returns as capture the minimal number of spaces at
the beginning of the lines of code]]
AutoGobbleSyntax = 
    ( space ^ 0 * P "\r" ) ^ -1 
    * Cf (
           (
             ( P " " ) ^ 0 * P "\r"
             + 
             Cf ( Cc(0) * ( P " " * Cc(1) ) ^ 0 , add )
             * ( 1 - P " " ) * ( 1 - P "\r" ) ^ 0 * P "\r"
           ) ^ 0
           *
           ( Cf ( Cc(0) * ( P " " * Cc(1) ) ^ 0 , add )
           * ( 1 - P " " ) * ( 1 - P "\r" ) ^ 0 ) ^ -1 ,
           math.min
         )

function AutoGobbleParse(code)
  local n = AutoGobbleSyntax:match(code)
  if n==0
  then Parse(code)
  else define_gobble_syntax(n)
       GobbleParse(code) 
  end 
end


--[[ The following LPEG returns as capture the number of spaces at the last line,
that is to say begin the \end{Piton} ]]

EnvGobbleSyntax =
       ( ( 1 - P "\r" ) ^ 0 * P "\r" ) ^ 0 
         * Cf ( Cc(0) * ( P " " * Cc(1) ) ^ 0 , add ) * -1

function EnvGobbleParse(code)
  local n = EnvGobbleSyntax:match(code)
  if n==0
  then Parse(code)
  else define_gobble_syntax(n)
       GobbleParse(code) 
  end 
end
\end{luacode*}
%    \end{macrocode}
%
% \vspace{1cm}
% \section{History}
%
% 
% \subsection*{Changes between versions 0.6 and 0.7}
% 
% New keys |resume|, |splittable| and |background-color| in |\PitonOptions|.
%
% The file |piton.lua| has been embedded in the file |piton.sty|. That means
% that the extension \pkg{piton} is now entirely contained in the file |piton.sty|.
% 
% \subsection*{Changes between versions 0.7 and 0.8}
% 
% New keys |footnote| and |footnotehyper| at load-time.
%
% New key |left-margin|.
%
% \end{document}
% 
%
% Local Variables:
% TeX-fold-mode: t
% TeX-fold-preserve-comments: nil
% flyspell-mode: nil
% fill-column: 80
% End:






