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+% \iffalse meta-comment
+%
+% Copyright (C) 2015-2020 by Emmanuel Beffara
+%
+% 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.
+%
+%<*driver>
+\documentclass[full]{l3doc}
+\usepackage{ebproof}
+\usepackage{multicol}
+\usepackage{tikz}
+\usetikzlibrary{decorations.pathmorphing}
+\EnableCrossrefs
+\newenvironment{example}{%
+ \VerbatimEnvironment
+ \begin{VerbatimOut}{example.tex}}{%
+ \end{VerbatimOut}
+ \begin{center}
+ \begin{minipage}{.4\textwidth}
+ \input{example.tex}
+ \end{minipage}%
+ \begin{minipage}{.6\textwidth}
+ \small\VerbatimInput[gobble=0]{example.tex}
+ \end{minipage}%
+ \end{center}
+}
+\begin{document}
+ \DocInput{\jobname.dtx}
+\end{document}
+%</driver>
+% \fi
+%
+% \title{^^A
+% The \pkg{ebproof} package \\
+% Formal proofs in the style of sequent calculus^^A
+% }
+%
+% \author{^^A
+% Emmanuel Beffara\thanks
+% {^^A
+% E-mail: \href{mailto:manu@beffara.org}{manu@beffara.org}^^A
+% }^^A
+% }
+%
+% \date{Version 2.1 -- Released 2020-08-19}
+%
+% \maketitle
+%
+% \setcounter{tocdepth}{2}
+% \begin{multicols}{2}
+% \tableofcontents
+% \end{multicols}
+%
+% \begin{documentation}
+%
+% \section{Introduction}
+%
+% The \pkg{ebproof} package provides commands to typeset proof trees, in the
+% style of sequent calculus and related systems:
+%
+% \begin{example}
+% \begin{prooftree}
+% \hypo{ \Gamma, A &\vdash B }
+% \infer1[abs]{ \Gamma &\vdash A\to B }
+% \hypo{ \Gamma \vdash A }
+% \infer2[app]{ \Gamma \vdash B }
+% \end{prooftree}
+% \end{example}
+%
+% The structure is very much inspired by the
+% \href{http://math.ucsd.edu/~sbuss/ResearchWeb/bussproofs/}{\pkg{bussproofs}}
+% package, in particular for the postfix notation.
+% I actually wrote \pkg{ebproof} because there were some limitations in
+% \pkg{bussproofs} that I did not know how to lift, and also because I did
+% not like some choices in that package (and also because it was fun to write).
+%
+% Any feedback is welcome, in the form of bug reports, feature requests or
+% suggestions, through the web page of the project at \url{https://framagit.org/manu/ebproof}.
+%
+% \section{Environments}
+%
+% \begin{function}{prooftree,prooftree*}
+% \begin{syntax}
+% \verb|\begin{prooftree}|\oarg{options}
+% ~ \meta{statements}
+% \verb|\end{prooftree}|
+% \end{syntax}
+% The package provides the \env{prooftree} environment, in standard and
+% starred variants.
+% This typesets the proof tree described by the \meta{statements}, as
+% described in section~\ref{sec:statements}.
+% The \meta{options} provide default formatting options for the proof tree,
+% available options are described in section~\ref{sec:options}.
+%
+% Following the conventions of \pkg{amsmath} for alignment environments, the
+% non-starred version produces a proof tree at the current position in the
+% text flow (it can be used in math mode or text mode) while the starred
+% version typesets the proof on a line of its own, like a displayed formula.
+% \end{function}
+%
+% \begin{example}
+% \[
+% \begin{prooftree}
+% \infer0{ \vdash A }
+% \hypo{ \vdash B } \infer1{ \vdash B, C }
+% \infer2{ \vdash A\wedge B, C }
+% \end{prooftree}
+% \quad \rightsquigarrow \quad
+% \begin{prooftree}
+% \infer0{ \vdash A } \hypo{ \vdash B }
+% \infer2{ \vdash A\wedge B }
+% \infer1{ \vdash A\wedge B, C }
+% \end{prooftree}
+% \]
+% \end{example}
+%
+% \section{Statements}
+% \label{sec:statements}
+%
+% Statements describe proofs in postfix notation: when typesetting a proof tree
+% whose last rule has, say, two premisses, you will first write statements for
+% the subtree of the first premiss, then statements for the subtree of the
+% second premiss, then a statement like \cs{infer2}\{\meta{conclusion}\} to
+% build an inference with these two subtrees as premisses and the given text as
+% conclusion.
+%
+% Hence statements operate on a stack of proof trees.
+% At the beginning of a \env{prooftree} environment, the stack is empty.
+% At the end, it must contain exactly one tree, which is the one that will be
+% printed.
+%
+% Note that the commands defined in this section only exist right inside
+% \env{prooftree} environments.
+% If you have a macro with the same name as one of the statements, for instance
+% \cs{hypo}, then this macro will keep its meaning outside \env{prooftree}
+% environments as well as inside the arguments of a statement.
+% If you really need to access the statements in another context, you can can
+% always call them by prefixing their names with \texttt{ebproof}, for instance as
+% \cs{ebproofhypo}.
+%
+% \subsection{Basic statements}
+%
+% The basic statements for building proofs are the following, where
+% \meta{options} stands for arbitrary options as described in
+% section~\ref{sec:options}.
+%
+% \begin{function}{\hypo}
+% \begin{syntax}
+% \cs{hypo}\oarg{options}\marg{text}
+% \end{syntax}
+% The statement \cs{hypo} pushes a new proof tree consisting only in one
+% conclusion line, with no premiss and no line above, in other words a tree
+% with only a leaf (\cs{hypo} stands for \emph{hypothesis}).
+% \end{function}
+%
+% \begin{function}{\infer}
+% \begin{syntax}
+% \cs{infer}\oarg{options}\meta{arity}\oarg{label}\marg{text}
+% \end{syntax}
+% The statement \cs{infer} builds an inference step by taking some proof
+% trees from the top of the stack, assembling them with a rule joining their
+% conclusions and putting a new conclusion below.
+% The \meta{arity} is the number of sub-proofs, it may be any number
+% including 0 (in this case there will be a line above the conclusion but no
+% sub-proof).
+% If \meta{label} is present, it is used as the label on the right of the
+% inference line; it is equivalent to using the \cmd{right label} option.
+% \end{function}
+%
+% \medskip
+%
+% The \meta{text} in these statements is the contents of the conclusion at the
+% root of the tree that the statements create.
+% It is typeset in math mode by default but any kind of formatting can be used
+% instead, using the \cmd{template} option.
+% The \meta{label} text is formatted in horizontal text mode by default.
+%
+% Each proof tree has a vertical axis, used for alignment of successive steps.
+% The position of the axis is deduced from the text of the conclusion at the
+% root of the tree: if \meta{text} contains the alignment character \verb|&|
+% then the axis is set at that position, otherwise the axis is set at the center
+% of the conclusion text.
+% The \cs{infer} statement makes sure that the axis of the premiss is at the
+% same position as the axis of the conclusion.
+% If there are several premisses, it places the axis at the center between the
+% left of the leftmost conclusion and the right of the rightmost conclusion:
+%
+% \begin{example}
+% \begin{prooftree}
+% \hypo{ &\vdash A, B, C }
+% \infer1{ A &\vdash B, C }
+% \infer1{ A, B &\vdash C }
+% \hypo{ D &\vdash E }
+% \infer2{ A, B, D &\vdash C, E }
+% \infer1{ A, B &\vdash C, D, E }
+% \infer1{ A &\vdash B, C, D, E }
+% \end{prooftree}
+% \end{example}
+%
+% \begin{function}{\ellipsis}
+% \begin{syntax}
+% \cs{ellipsis}\marg{label}\marg{text}
+% \end{syntax}
+% The statement \cs{ellipsis} typesets vertical dots, with a label on the right,
+% and a new conclusion. No inference lines are inserted.
+% \end{function}
+%
+% \begin{example}
+% \begin{prooftree}
+% \hypo{ \Gamma &\vdash A }
+% \ellipsis{foo}{ \Gamma &\vdash A, B }
+% \end{prooftree}
+% \end{example}
+%
+%
+% \subsection{Modifying proof trees}
+%
+% The following additional statements may be used to affect the format of the
+% last proof tree on the stack.
+%
+% \begin{function}{\rewrite}
+% \begin{syntax}
+% \cs{rewrite}\marg{code}
+% \end{syntax}
+% The statement \cs{rewrite} is used to modify the proof of the stack while
+% preserving its size and alignment.
+% The \meta{code} is typeset in horizontal mode, with the following control
+% sequences defined:
+% \begin{itemize}
+% \item \cs{treebox} is a box register that contains the original material,
+% \item \cs{treemark}\marg{name} expands as the position of a given mark with
+% respect to the left of the box.
+% \end{itemize}
+% \end{function}
+%
+% A simple use of this statement is to change the color of a proof tree:
+% \begin{example}
+% \begin{prooftree}
+% \hypo{ \Gamma, A &\vdash B }
+% \infer1[abs]{ \Gamma &\vdash A\to B }
+% \rewrite{\color{red}\box\treebox}
+% \hypo{ \Gamma \vdash A }
+% \infer2[app]{ \Gamma \vdash B }
+% \end{prooftree}
+% \end{example}
+% Note the absence of spaces inside the call to \cs{rewrite}, because spaces
+% would affect the position of the tree box.
+% Note also that explicit use of \cs{treebox} is required to actually draw the
+% subtree.
+% Not using it will effectively not render the subtree, while still reserving
+% its space in the enclosing tree:
+% \begin{example}
+% \begin{prooftree}
+% \hypo{ \Gamma, A &\vdash B }
+% \infer1[abs]{ \Gamma &\vdash A\to B }
+% \rewrite{}
+% \hypo{ \Gamma \vdash A }
+% \infer2[app]{ \Gamma \vdash B }
+% \end{prooftree}
+% \end{example}
+% This kind of manipulation is useful for instance in conjunction with the
+% \pkg{beamer} package to allow revealing subtrees of a proof tree
+% progressively in successive slides of a given frame.
+%
+% \begin{function}{\delims}
+% \begin{syntax}
+% \cs{delims}\marg{left}\marg{right}
+% \end{syntax}
+% The statement \cs{delims} puts left and right delimiters around the whole
+% sub-proof, without changing the alignment (the spacing is affected by the
+% delimiters, however).
+% The \meta{left} text must contain an opening occurrence of \cs{left} and
+% the \meta{right} text must contain a matching occurrence of \cs{right}.
+% For instance, \verb|\delims{\left(}{\right)}| will put the sub-proof
+% between parentheses.
+% \end{function}
+%
+% \begin{example}
+% \begin{prooftree}
+% \hypo{ A_1 \vee \cdots \vee A_n }
+% \hypo{ [A_i] }
+% \ellipsis{}{ B }
+% \delims{ \left( }{ \right)_{1\leq i\leq n} }
+% \infer2{ B }
+% \end{prooftree}
+% \end{example}
+%
+% \begin{function}{\overlay}
+% \begin{syntax}
+% \cs{overlay}
+% \end{syntax}
+% The statement \cs{overlay} combines the last two proofs on the stack into
+% a single one, so that their conclusions are placed at the same point.
+% \end{function}
+%
+% \begin{example}
+% \begin{prooftree}
+% \hypo{Z}
+% \hypo{A} \hypo{B} \infer2{C} \hypo{D} \infer2{D}
+% \rewrite{\color{blue}\box\treebox}
+% \hypo{E} \hypo{F} \hypo{G} \infer2{H} \infer2{I}
+% \rewrite{\color{red}\box\treebox}
+% \overlay \hypo{J} \infer3{K}
+% \end{prooftree}
+% \end{example}
+%
+% The primary use of this feature is for building animated presentations where
+% a subtree in a proof has to be modified without affecting the general
+% alignment of the surrounding proof. For instance, the example above could be
+% used in Beamer to build successive slides in a given frame with two
+% different subtrees:
+%
+% \begin{verbatim}
+% \begin{prooftree}
+% \hypo{Z}
+% \hypo{A} \hypo{B} \infer2{C} \hypo{D} \infer2{D}
+% \only<2>{\rewrite{}} % erases this version on slide 2
+% \hypo{E} \hypo{F} \hypo{G} \infer2{H} \infer2{I}
+% \only<1>{\rewrite{}} % erases this version on slide 1
+% \overlay \hypo{J} \infer3{K}
+% \end{prooftree}
+% \end{verbatim}
+%
+% \section{Options}
+% \label{sec:options}
+%
+% The formatting of trees, conclusion texts and inference rules is affected by
+% options, specified using the \LaTeX3 key-value system.
+% All options are in the \texttt{ebproof} module in the key tree.
+% They can be set locally for a proof tree or for a single statement using
+% optional arguments in the associated commands.
+%
+% \begin{function}{\ebproofset,\set}
+% \begin{syntax}
+% \cs{ebproofset}\marg{options}
+% \end{syntax}
+% The statement \cs{ebproofset} is used to set some options. When used
+% inside a \env{prooftree} environment, it can written \cs{set}.
+% The options will apply in the current scope; using this in preamble will
+% effectively set options globally.
+% Specific options may also be specified for each proof tree and for each
+% statement in a proof tree, using optional arguments.
+% \end{function}
+%
+% \subsection{General shape}
+%
+% The options in this section only make sense at the global level and at the
+% proof level.
+% Changing the proof style inside a \env{proof} environment has undefined
+% behaviour.
+%
+% \begin{variable}{proof style}
+% The option \cmd{proof style} sets the general shape for representing proofs.
+% The following styles are provided:
+% \begin{description}
+% \item[upwards]
+% This is the default style.
+% Proof trees grow upwards, with conclusions below and premisses above.
+% \item[downwards]
+% Proof trees grow downwards, with conclusions above and premisses below.
+% \fvset{gobble=6}
+% \begin{example}
+% \begin{prooftree}[proof style=downwards]
+% \hypo{ \Gamma, A &\vdash B }
+% \infer1[abs]{ \Gamma &\vdash A\to B }
+% \hypo{ \Gamma \vdash A }
+% \infer2[app]{ \Gamma \vdash B }
+% \end{prooftree}
+% \end{example}
+% \end{description}
+% \end{variable}
+%
+% In the optional argument of \env{prooftree} environments, proof styles can
+% be specified directly, without prefixing the name by ``\texttt{proof style=}''.
+% For instance, the first line of the example above could be written
+% \verb|\begin{prooftree}| equivalently.
+%
+% \begin{variable}{center}
+% The option \cmd{center} toggles vertical centering of typeset proofs.
+% If set to \texttt{true}, the tree produced by the \env{prooftree}
+% environment will be vertically centered around the text line.
+% If set to \texttt{false}, the base line of the tree will be the base line
+% of the conclusion.
+% The default value is \texttt{true}.
+% \end{variable}
+%
+% \begin{example}
+% \begin{prooftree}[center=false]
+% \infer0{ A \vdash A }
+% \end{prooftree}
+% \qquad
+% \begin{prooftree}[center=false]
+% \hypo{ \Gamma, A \vdash B }
+% \infer1{ \Gamma \vdash A \to B }
+% \end{prooftree}
+% \end{example}
+%
+% \subsection{Spacing}
+%
+% \begin{variable}{separation}
+% Horizontal separation between sub-proofs in an inference is defined by the
+% option \cmd{separation}.
+% The default value is \texttt{1.5em}.
+% \end{variable}
+%
+% \begin{example}
+% \begin{prooftree}[separation=0.5em]
+% \hypo{ A } \hypo{ B } \infer2{ C }
+% \hypo{ D } \hypo{ E } \hypo{ F } \infer3{ G }
+% \hypo{ H } \infer[separation=3em]3{ K }
+% \end{prooftree}
+% \end{example}
+%
+% \begin{variable}{rule margin}
+% The spacing above and below inference lines is defined by the option
+% \cmd{rule margin}.
+% The default value is \texttt{0.7ex}.
+% \end{variable}
+%
+% \begin{example}
+% \begin{prooftree}[rule margin=2ex]
+% \hypo{ \Gamma, A &\vdash B }
+% \infer1[abs]{ \Gamma &\vdash A\to B }
+% \hypo{ \Gamma \vdash A }
+% \infer2[app]{ \Gamma \vdash B }
+% \end{prooftree}
+% \end{example}
+%
+% \subsection{Shape of inference lines}
+%
+% \begin{variable}{rule style}
+% The shape of inference lines is set by the option \cmd{rule style}.
+% The following values are provided:
+% \begin{center}
+% \begin{tabular}{@{}l@{\qquad}l@{}}
+% \toprule
+% \cmd{simple} & a simple line (this is the default style) \\
+% \cmd{no rule} & no rule, only a single space of length \texttt{rule margin} \\
+% \cmd{double} & a double line \\
+% \cmd{dashed} & a single dashed line \\
+% \bottomrule
+% \end{tabular}
+% \end{center}
+% \end{variable}
+%
+% The precise rendering is influenced by parameters specified below.
+% Arbitrary new shapes can defined using the \cs{ebproofnewrulestyle} command
+% described in section~\ref{sec:styles}, using \texttt{rule code} option
+% described below.
+%
+% In the optional argument of the \cs{infer} statement, rule styles can be
+% specified directly, without prefixing the style name by ``\texttt{rule style=}''.
+% For instance, \verb|\infer[dashed]| is equivalent to
+% \verb|\infer[rule style=dashed]|.
+%
+% \begin{example}
+% \begin{prooftree}
+% \hypo{ \Gamma &\vdash A \to B }
+% \infer[no rule]1{ \Gamma &\vdash {!A} \multimap B }
+% \hypo{ \Delta &\vdash A }
+% \infer[rule thickness=2pt]1{ \Delta &\vdash {!A} }
+% \infer0{ B \vdash B }
+% \infer[dashed]2{ \Delta, {!A}\multimap B \vdash B }
+% \infer2{ \Gamma, \Delta &\vdash B }
+% \infer[double]1{ \Gamma \cup \Delta &\vdash B }
+% \end{prooftree}
+% \end{example}
+%
+% \begin{variable}{rule thickness,rule separation}
+% The thickness of inference lines is defined by option \cmd{rule
+% thickness}, it is \texttt{0.4pt} by default.
+% The distance between the two lines in the \texttt{double} rule style is
+% defined by the \cmd{rule separation} option.
+% It is \texttt{2pt} by default.
+% \end{variable}
+% \begin{variable}{rule dash length,rule dash space}
+% For dashed rules, the length of dashes is defined by the option
+% \cmd{rule dash length} and the space between dashes is defined by the
+% option \cmd{rule dash space}.
+% The default values are \texttt{0.2em} and \texttt{0.3em} respectively.
+% \end{variable}
+%
+% \begin{variable}{rule code}
+% Arbitrary rule shapes can be optained using the \cmd{rule code} option.
+% The argument is code is used to render the rule, it is executed in
+% vertical mode in a \cs{vbox} whose \cs{hsize} is set to the width of the
+% rule.
+% Margins above and below are inserted automatically (they can be removed by
+% setting \texttt{rule margin} to \texttt{0pt}).
+% \end{variable}
+%
+% \begin{example}
+% \begin{prooftree}[rule code={\hbox{\tikz
+% \draw[decorate,decoration={snake,amplitude=.3ex}]
+% (0,0) -- (\hsize,0);}}]
+% \hypo{ \Gamma &\vdash A }
+% \infer1{ \Gamma &\vdash A, \ldots, A }
+% \hypo{ \Delta, A, \ldots, A \vdash \Theta }
+% \infer2{ \Gamma, \Delta \vdash \Theta }
+% \end{prooftree}
+% \end{example}
+% Note that this example requires the \pkg{tikz} package, with the
+% \pkg{decorations.pathmorphing} library for the \texttt{snake} decoration.
+%
+% \subsection{Format of conclusions and labels}
+%
+% \begin{variable}{template,left template,right template}
+% The format of text in inferences is defined by templates.
+% The option \cmd{template} is used for text with no alignment mark, the
+% options \cmd{left template} and \cmd{right template} are used for the left
+% and right side of the alignment mark when it is present.
+% The value of these options is arbitrary \TeX\ code, composed in horizontal mode.
+% The macro \cs{inserttext} is used to insert the actual text passed to the
+% \cs{hypo} and \cs{infer} statements.
+% The default value for \cmd{template} is simply \verb|$\inserttext$|, so
+% that conclusions are set in math mode.
+% The default values for \cmd{left template} and \cmd{right template} are
+% similar, with spacing assuming that a relation symbol is put near the
+% alignment mark, so that \verb|\infer1{A &\vdash B}| is spaced correctly.
+% \end{variable}
+%
+% \begin{example}
+% \begin{prooftree}[template=(\textbf\inserttext)]
+% \hypo{ foo }
+% \hypo{ bar }
+% \infer1{ baz }
+% \infer2{ quux }
+% \end{prooftree}
+% \end{example}
+%
+% \begin{variable}{left label,right label}
+% The text to use as the labels of the rules, on the left and on the right
+% of the inference line, is defined by the options \cmd{left label} and
+% \cmd{right label}.
+% Using the second optional argument in \cs{infer} is equivalent to setting
+% the \env{right label} option with the value of that argument.
+% \end{variable}
+%
+% \begin{example}
+% \begin{prooftree}
+% \hypo{ \Gamma, A &\vdash B }
+% \infer[left label=$\lambda$]1[abs]
+% { \Gamma &\vdash A\to B }
+% \hypo{ \Gamma \vdash A }
+% \infer[left label=@]2[app]{ \Gamma \vdash B }
+% \end{prooftree}
+% \end{example}
+%
+% \begin{variable}{left label template,right label template}
+% Similarly to conclusions, labels are formatted according to templates.
+% The code is arbitrary \TeX\ code, composed in horizontal mode, where the
+% macro \cs{inserttext} can be used to insert the actual label text.
+% The default values are simply \cs{inserttext} so that labels are set in
+% plain text mode.
+% \end{variable}
+% \begin{variable}{label separation}
+% The spacing between an inference line and its labels is defined by the
+% option \cmd{label separation}, the default value is \texttt{0.5em}.
+% The height of the horizontal axis used for aligning the labels with the
+% rules is defined by the option \cmd{label axis}, the default value is
+% \texttt{0.5ex}.
+% \end{variable}
+%
+%
+% \subsection{Style macros}
+% \label{sec:styles}
+%
+% The following commands allow for the definition of custom styles using the
+% basic style options, in a way similar to PGF's ``styles'' and \LaTeX3's
+% ``meta-keys''.
+% This allows setting a bunch of options with the same values in many proofs
+% using a single definition.
+%
+% \begin{function}{\ebproofnewstyle}
+% \begin{syntax}
+% \cs{ebproofnewstyle}\marg{name}\marg{options}
+% \end{syntax}
+% The statement \cs{ebproofnewstyle} defines a new style option with some
+% \meta{name} that sets a given set of \meta{options}.
+% \end{function}
+% For instance, the following code defines a new option \cmd{small} that sets
+% various parameters so that proofs are rendered smaller.
+% \begin{example}
+% \ebproofnewstyle{small}{
+% separation = 1em, rule margin = .5ex,
+% template = \footnotesize$\inserttext$ }
+% \begin{prooftree}[small]
+% \hypo{ \Gamma, A \vdash B }
+% \infer1{ \Gamma \vdash A\to B }
+% \hypo{ \Gamma \vdash A } \infer2{ \Gamma \vdash B }
+% \end{prooftree}
+% \end{example}
+%
+% \begin{function}{\ebproofnewrulestyle}
+% \begin{syntax}
+% \cs{ebproofnewrulestyle}\marg{name}\marg{options}
+% \end{syntax}
+% The statement \cs{ebproofnewrulestyle} does the same for rule styles.
+% The \meta{options} part includes options used to set how to draw rules in
+% the new style.
+% \end{function}
+%
+% The option \cmd{rule code} is useful in this command as it allows to
+% define arbitrary rule styles.
+% For instance, the squiggly rule example above could be turned into a new
+% rule style \texttt{zigzag} with the following code:
+% \begin{example}
+% \ebproofnewrulestyle{zigzag}{
+% rule code = {\hbox{\tikz
+% \draw[decorate,decoration={snake,amplitude=.3ex}]
+% (0,0) -- (\hsize,0);}}}
+% \begin{prooftree}
+% \hypo{ \Gamma &\vdash A }
+% \infer1{ \Gamma &\vdash A, \ldots, A }
+% \hypo{ \Delta, A, \ldots, A \vdash \Theta }
+% \infer[zigzag]2{ \Gamma, \Delta \vdash \Theta }
+% \end{prooftree}
+% \end{example}
+%
+%
+% \section{License}
+%
+% This work 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
+% \begin{center}
+% \url{http://www.latex-project.org/lppl.txt}
+% \end{center}
+% and version 1.3 or later is part of all distributions of \LaTeX\
+% version 2005/12/01 or later.
+%
+% This work has the LPPL maintenance status `maintained'.
+%
+% The Current Maintainer of this work is Emmanuel Beffara.
+%
+% This work consists of the files \texttt{ebproof.sty} and \texttt{ebproof.tex}.
+%
+% \section{History}
+%
+% This section lists the principal evolutions of the package, in reverse
+% chronological order.
+% \begin{description}
+% \item[Version 2.1 (2020-08-19)]
+% Mostly a bugfix release.
+% \begin{itemize}
+% \item Makes the \env{prooftree} environment robust to use in tabular
+% contexts.
+% \item Adds the \cs{overlay} statement.
+% \item Fixes a compatibility issue with \LaTeX\ release 2020-10-01.
+% \end{itemize}
+% \item[Version 2.0 (2017-05-17)]
+% A complete rewrite of the code using the \LaTeX3 programming environment.
+% The incompatible changes from the user's point of view are the following:
+% \begin{itemize}
+% \item Proof statements are now writtten in lowercase ({i.e.} \cs{Infer} is
+% now written \cs{infer} etc.) but the syntax is otherwise unchanged.
+% The old uppercase commands still work but produce a deprecation warning,
+% they will be removed in a future version.
+% \item New styles are now defined using \cs{ebproofnewstyle} and
+% \cs{ebproofnewrulestyle}. The previous method using PGF styles does not
+% work anymore (because PGF is not used anymore).
+% \end{itemize}
+% The new commands and options are the following:
+% \begin{itemize}
+% \item The statement \cs{rewrite} generalizes \cs{Alter},
+% \item The option \cmd{label axis} controls vertical alignment of labels.
+% \end{itemize}
+% \item[Version 1.1 (2015-03-13)]
+% A bugfix release.
+% In \cmd{template} options, one now uses \cs{inserttext} instead of \verb|#1|
+% for the text arguments, which improves robustness.
+% \item[Version 1.0 (2015-02-04)]
+% The first public release.
+% \end{description}
+%
+% \end{documentation}
+%
+% \clearpage \appendix
+%
+% \begin{implementation}
+%
+% \section{Implementation}
+%
+% \begin{macrocode}
+%<*package>
+\NeedsTeXFormat{LaTeX2e}
+\RequirePackage{expl3}
+\RequirePackage{xparse}
+\ProvidesExplPackage{ebproof}{2020/08/19}{2.1}{EB's proof trees}
+%<@@=ebproof>
+% \end{macrocode}
+%
+% \subsection{Parameters}
+%
+% We first declare all options. For the meaning of options, see
+% section~\ref{sec:options}.
+%
+% \begin{macrocode}
+\keys_define:nn { ebproof } {
+center .bool_set:N = \l_@@_center_bool,
+proof~style .choice: ,
+proof~style / upwards .code:n = \bool_set_false:N \l_@@_updown_bool,
+proof~style / downwards .code:n = \bool_set_true:N \l_@@_updown_bool,
+separation .dim_set:N = \l_@@_separation_dim,
+rule~margin .dim_set:N = \l_@@_rule_margin_dim,
+rule~thickness .dim_set:N = \l_@@_rule_thickness_dim,
+rule~separation .dim_set:N = \l_@@_rule_separation_dim,
+rule~dash~length .dim_set:N = \l_@@_rule_dash_length_dim,
+rule~dash~space .dim_set:N = \l_@@_rule_dash_space_dim,
+rule~code .tl_set:N = \l_@@_rule_code_tl,
+rule~style .choice:,
+template .tl_set:N = \l_@@_template_tl,
+left~template .tl_set:N = \l_@@_left_template_tl,
+right~template .tl_set:N = \l_@@_right_template_tl,
+left~label .tl_set:N = \l_@@_left_label_tl,
+right~label .tl_set:N = \l_@@_right_label_tl,
+left~label~template .tl_set:N = \l_@@_left_label_template_tl,
+right~label~template .tl_set:N = \l_@@_right_label_template_tl,
+label~separation .dim_set:N = \l_@@_label_separation_dim,
+label~axis .dim_set:N = \l_@@_label_axis_dim,
+}
+% \end{macrocode}
+%
+% \begin{macro}{\ebproofnewrulestyle}
+% We then define the document-level macro \cs{ebproofnewrulestyle} and use
+% it to define the default styles. This simply consists in defining a
+% meta-key.
+% \begin{macrocode}
+\NewDocumentCommand \ebproofnewrulestyle { mm } {
+ \keys_define:nn { ebproof } {
+ rule~style / #1 .meta:nn = { ebproof } { #2 }
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% The styles |simple|, |no rule| and |double| are defined in a straightforward
+% way.
+%
+% \begin{macrocode}
+\ebproofnewrulestyle { simple } {
+ rule~code = { \tex_hrule:D height \l_@@_rule_thickness_dim }
+}
+\ebproofnewrulestyle { no~rule } {
+ rule~code =
+}
+\ebproofnewrulestyle { double } {
+ rule~code = {
+ \tex_hrule:D height \l_@@_rule_thickness_dim
+ \skip_vertical:N \l_@@_rule_separation_dim
+ \tex_hrule:D height \l_@@_rule_thickness_dim
+ }
+}
+% \end{macrocode}
+%
+% The |dashed| style uses leaders and filling for repeating a single dash. We
+% use \TeX\ primitives that have no \LaTeX3 counterpart for this.
+%
+% \begin{macrocode}
+\ebproofnewrulestyle { dashed } {
+ rule~code = {
+ \hbox_to_wd:nn { \tex_hsize:D } {
+ \dim_set:Nn \l_tmpa_dim { \l_@@_rule_dash_space_dim / 2 }
+ \skip_horizontal:n { -\l_tmpa_dim }
+ \tex_cleaders:D \hbox:n {
+ \skip_horizontal:N \l_tmpa_dim
+ \tex_vrule:D
+ height \l_@@_rule_thickness_dim
+ width \l_@@_rule_dash_length_dim
+ \skip_horizontal:N \l_tmpa_dim
+ } \tex_hfill:D
+ \skip_horizontal:n { -\l_tmpa_dim }
+ }
+ }
+}
+% \end{macrocode}
+%
+% Now we can define the default values, including the default rule style.
+%
+% \begin{macrocode}
+\keys_set:nn { ebproof } {
+ center = true,
+ proof~style = upwards,
+ separation = 1.5em,
+ rule~margin = .7ex,
+ rule~thickness = .4pt,
+ rule~separation = 2pt,
+ rule~dash~length = .2em,
+ rule~dash~space = .3em,
+ rule~style = simple,
+ template = $\inserttext$,
+ left~template = $\inserttext\mathrel{}$,
+ right~template = $\mathrel{}\inserttext$,
+ left~label = ,
+ right~label = ,
+ left~label~template = \inserttext,
+ right~label~template = \inserttext,
+ label~separation = 0.5em,
+ label~axis = 0.5ex
+}
+% \end{macrocode}
+%
+% \begin{macro}{\ebproofnewstyle}
+% Defining a style simply means defining a meta-key.
+% \begin{macrocode}
+\NewDocumentCommand \ebproofnewstyle { mm } {
+ \keys_define:nn { ebproof } { #1 .meta:n = { #2 } }
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \subsection{Proof boxes}
+%
+% \TeX\ does not actually provide data structures, so we have to encode things.
+% We provide an allocator for ``registers'' holding boxes with attributes. Such
+% a register consists in a box register and a property list for marks, which
+% maps mark names to values as explicit dimensions with units.
+%
+% \begin{macro}{\@@_new:N}
+% Using only public interfaces forces a convoluted approach to allocation:
+% we use a global counter \cs{g_ebproof_register_int} to number registers,
+% then each allocation creates registers named \cs{g_ebproof_K_N} where K is
+% the kind of component (box or marks) and N is the identifier of the
+% register. The proof box register itself only contains the identifier used
+% for indirection.
+% \begin{macrocode}
+\int_new:N \g_@@_register_int
+\cs_new:Nn \@@_box:N { g__ebproof_box_ \tl_use:N #1 }
+\cs_new:Nn \@@_marks:N { g__ebproof_marks_ \tl_use:N #1 }
+\cs_new:Nn \@@_new:N {
+ \tl_new:N #1
+ \int_gincr:N \g_@@_register_int
+ \tl_gset:Nx #1 { \int_to_arabic:n { \g_@@_register_int } }
+ \box_new:c { \@@_box:N #1 }
+ \prop_new:c { \@@_marks:N #1 }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_clear:N}
+% The box is cleared by setting it to an empty hbox.
+% Using \cs{box_clear:N} instead would not work because trying to push this
+% box on the stack would not actually append any box.
+% \begin{macrocode}
+\cs_new:Nn \@@_clear:N {
+ \hbox_set:cn { \@@_box:N #1 } {}
+ \prop_clear:c { \@@_marks:N #1 }
+ \@@_set_mark:Nnn #1 { left } { 0pt }
+ \@@_set_mark:Nnn #1 { right } { 0pt }
+ \@@_set_mark:Nnn #1 { axis } { 0pt }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Mark operations}
+%
+% \begin{macro}{\@@_set_mark:Nnn}
+% Setting the value of a mark uses a temporary register to evaluate the
+% dimension expression because values are stored textually in a property
+% list.
+% \begin{macrocode}
+\dim_new:N \l_@@_transit_dim
+\cs_new:Nn \@@_set_mark:Nnn {
+ \dim_set:Nn \l_@@_transit_dim { #3 }
+ \prop_put:cnV { \@@_marks:N #1 } { #2 }
+ \l_@@_transit_dim
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_mark:Nn}
+% Getting the value of a mark simply consists in getting an item in a
+% property list.
+% \begin{macrocode}
+\cs_new:Nn \@@_mark:Nn {
+ \prop_item:cn { \@@_marks:N #1 } { #2 }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_shift_x:Nn}
+% This function shifts the marks by a specified amount, without modifying
+% the box.
+% \begin{macrocode}
+\cs_new:Nn \@@_shift_x:Nn {
+ \prop_map_inline:cn { \@@_marks:N #1 } {
+ \@@_set_mark:Nnn #1 { ##1 } { ##2 + #2 }
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_enlarge_conclusion:NN}
+% This function moves the left and right marks of the first tree so that
+% they are at least as far from the axis as they are in the second tree.
+% For instance we get the following:
+% \begin{center}
+% \begin{tikzpicture}[y=-3ex]
+% \node (L1) at (1,0) {L}; \node (A1) at (2,0) {A}; \node (R1) at (4,0) {R};
+% \node (L2) at (0,1) {L}; \node (A2) at (2,1) {A}; \node (R2) at (3,1) {R};
+% \node (L3) at (0,2) {L}; \node (A3) at (2,2) {A}; \node (R3) at (4,2) {R};
+% \draw (L1) -- (A1) -- (R1);
+% \draw (L2) -- (A2) -- (R2);
+% \draw (L3) -- (A3) -- (R3);
+% \node[anchor=west] at (5,0) {box 1 before};
+% \node[anchor=west] at (5,1) {box 2 before};
+% \node[anchor=west] at (5,2) {box 1 after};
+% \end{tikzpicture}
+% \end{center}
+% The contents of the trees are unchanged.
+% \begin{macrocode}
+\cs_new:Nn \@@_enlarge_conclusion:NN {
+ \dim_set:Nn \l_tmpa_dim { \@@_mark:Nn #1 {axis}
+ + \@@_mark:Nn #2 {left} - \@@_mark:Nn #2 {axis} }
+ \dim_compare:nNnT { \l_tmpa_dim } < { \@@_mark:Nn #1 {left} } {
+ \@@_set_mark:Nnn #1 {left} { \l_tmpa_dim } }
+ \dim_set:Nn \l_tmpa_dim { \@@_mark:Nn #1 {axis}
+ + \@@_mark:Nn #2 {right} - \@@_mark:Nn #2 {axis} }
+ \dim_compare:nNnT { \l_tmpa_dim } > { \@@_mark:Nn #1 {right} } {
+ \@@_set_mark:Nnn #1 {right} { \l_tmpa_dim } }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Building blocks}
+%
+% \begin{macro}{\@@_make_simple:Nn}
+% Make a tree with explicit material in horizontal mode. Set the left and
+% right marks to extremal positions and set the axis in the middle.
+% \begin{macrocode}
+\cs_new:Nn \@@_make_simple:Nn {
+ \hbox_set:cn { \@@_box:N #1 } { #2 }
+ \@@_set_mark:Nnn #1 { left } { 0pt }
+ \@@_set_mark:Nnn #1 { axis } { \box_wd:c { \@@_box:N #1 } / 2 }
+ \@@_set_mark:Nnn #1 { right } { \box_wd:c { \@@_box:N #1 } }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_make_split:Nnn}
+% Make a tree with explicit material in horizontal mode, split in two parts.
+% Set the left and right marks to extremal positions and set the axis
+% between the two parts.
+% \begin{macrocode}
+\cs_new:Nn \@@_make_split:Nnn {
+ \@@_set_mark:Nnn #1 { left } { 0pt }
+ \hbox_set:cn { \@@_box:N #1 } { #2 }
+ \@@_set_mark:Nnn #1 { axis } { \box_wd:c { \@@_box:N #1 } }
+ \hbox_set:cn { \@@_box:N #1 } { \hbox_unpack:c { \@@_box:N #1 } #3 }
+ \@@_set_mark:Nnn #1 { right } { \box_wd:c { \@@_box:N #1 } }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_make_vertical:Nnnn}
+% Make a tree with explicit material in vertical mode, using an explicit
+% width and axis.
+% \begin{macrocode}
+\cs_new:Nn \@@_make_vertical:Nnnn {
+ \@@_set_mark:Nnn #1 { left } { 0pt }
+ \@@_set_mark:Nnn #1 { axis } { #2 }
+ \@@_set_mark:Nnn #1 { right } { #3 }
+ \vbox_set:cn { \@@_box:N #1 } {
+ \dim_set:Nn \tex_hsize:D { \@@_mark:Nn #1 {right} }
+ #4
+ }
+ \box_set_wd:cn { \@@_box:N #1 } { \@@_mark:Nn #1 {right} }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Assembling boxes}
+%
+% \begin{macro}{\@@_extend:Nnnnn}
+% Extend a tree box. The marks are shifted so that alignment is preserved.
+% The arguments are dimensions for the left, top, right and bottom sides
+% respectively.
+% \begin{macrocode}
+\cs_new:Nn \@@_extend:Nnnnn {
+ \dim_compare:nNnF { #2 } = { 0pt } {
+ \hbox_set:cn { \@@_box:N #1 } {
+ \skip_horizontal:n { #2 }
+ \box_use:c { \@@_box:N #1 }
+ }
+ \@@_shift_x:Nn #1 { #2 }
+ }
+ \box_set_ht:Nn #1 { \box_ht:c { \@@_box:N #1 } + #3 }
+ \box_set_wd:Nn #1 { \box_wd:c { \@@_box:N #1 } + #4 }
+ \box_set_dp:Nn #1 { \box_dp:c { \@@_box:N #1 } + #5 }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_append_right:NnN}
+% Append the contents of the second tree to the first one on the right, with
+% matching baselines. The marks of both trees are preserved. The middle
+% argument specifies the space to insert between boxes.
+% \begin{macrocode}
+\cs_new:Nn \@@_append_right:NnN {
+ \hbox_set:cn { \@@_box:N #1 } {
+ \box_use:c { \@@_box:N #1 }
+ \dim_compare:nNnF { #2 } = { 0pt } { \skip_horizontal:n { #2 } }
+ \box_use:c { \@@_box:N #3 }
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_append_left:NnN}
+% Append the contents of the second tree to the first one on the left, with
+% matching baselines. The marks of the first tree are shifted accordingly.
+% The middle argument specifies the space to insert between boxes.
+% \begin{macrocode}
+\cs_new:Nn \@@_append_left:NnN {
+ \@@_shift_x:Nn #1 { \box_wd:c { \@@_box:N #3 } + #2 }
+ \hbox_set:cn { \@@_box:N #1 } {
+ \box_use:c { \@@_box:N #3 }
+ \dim_compare:nNnF { #2 } = { 0pt } { \skip_horizontal:n { #2 } }
+ \box_use:c { \@@_box:N #1 }
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_align:NN}
+% Shift one of two trees to the right so that their axes match. The marks of
+% the one that is shifted are updated accordingly.
+% \begin{macrocode}
+\cs_new:Nn \@@_align:NN {
+ \dim_set:Nn \l_tmpa_dim
+ { \@@_mark:Nn #2 {axis} - \@@_mark:Nn #1 {axis} }
+ \dim_compare:nNnTF \l_tmpa_dim < { 0pt } {
+ \@@_extend:Nnnnn #2 { -\l_tmpa_dim } { 0pt } { 0pt } { 0pt }
+ } {
+ \@@_extend:Nnnnn #1 { \l_tmpa_dim } { 0pt } { 0pt } { 0pt }
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_append_above:NN}
+% Append the contents of the second tree above the first one, with matching
+% axes. The marks of the first tree are preserved.
+% \begin{macrocode}
+\cs_new:Nn \@@_append_above:NN {
+ \@@_align:NN #1 #2
+ \vbox_set:cn { \@@_box:N #1 } {
+ \box_use:c { \@@_box:N #2 }
+ \tex_prevdepth:D -1000pt
+ \box_use:c { \@@_box:N #1 }
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_append_below:NN}
+% Append the contents of the second tree below the first one, with matching
+% axes. The marks of the first tree are preserved.
+% \begin{macrocode}
+\cs_new:Nn \@@_append_below:NN {
+ \@@_align:NN #1 #2
+ \vbox_set_top:Nn #1 {
+ \box_use:c { \@@_box:N #1 }
+ \tex_prevdepth:D -1000pt
+ \box_use:c { \@@_box:N #2 }
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_overlay:NN}
+% Append the second tree as an overlay over the first one, so that the
+% baselines and axes match. The bounding box of the result adjusts to
+% contain both trees.
+% \begin{macrocode}
+\cs_new:Nn \@@_overlay:NN {
+ \@@_align:NN #1 #2
+ \hbox_set:cn { \@@_box:N #1 } {
+ \hbox_overlap_right:n { \box_use:c { \@@_box:N #1 } }
+ \box_use:c { \@@_box:N #2 }
+ \dim_compare:nNnT
+ { \box_wd:c { \@@_box:N #2 } } < { \box_wd:c { \@@_box:N #1 } }
+ { \skip_horizontal:n
+ { \box_wd:c { \@@_box:N #1 } - \box_wd:c { \@@_box:N #2 } } }
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_vcenter:N}
+% Shift the material in a tree vertically so that the height and depth are
+% equal (like \TeX's \cs{vcenter} but around the baseline).
+% \begin{macrocode}
+\cs_new:Nn \@@_vcenter:N {
+ \dim_set:Nn \l_tmpa_dim
+ { ( \box_ht:c { \@@_box:N #1 } - \box_dp:c { \@@_box:N #1 } ) / 2 }
+ \box_set_eq:Nc \l_tmpa_box { \@@_box:N #1 }
+ \hbox_set:cn { \@@_box:N #1 }
+ { \box_move_down:nn { \l_tmpa_dim } { \box_use:N \l_tmpa_box } }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \subsection{Making inferences}
+%
+% The following commands use the parameters defined at the beginning of the
+% package for actually building proof trees using the commands defined above.
+%
+% \begin{macro}{\@@_append_vertical:NN}
+% Append the contents of the second tree above or below the first one,
+% depending on current settings. Axes are aligned and the marks of the first
+% tree are preserved.
+% \begin{macrocode}
+\cs_new:Nn \@@_append_vertical:NN {
+ \bool_if:NTF \l_@@_updown_bool
+ { \@@_append_below:NN #1 #2 }
+ { \@@_append_above:NN #1 #2 }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_make_rule_for:NNN}
+% Make a box containing an inference rule with labels, using the current
+% settings. The width and axis position are taken as those of the conclusion
+% of another tree box. The third argument is used as a temporary register
+% for building labels.
+% \begin{macrocode}
+\cs_new:Nn \@@_make_rule_for:NNN {
+% \end{macrocode}
+% Build the rule.
+% \begin{macrocode}
+ \@@_make_vertical:Nnnn #1
+ { \@@_mark:Nn #2 {axis} - \@@_mark:Nn #2 {left} }
+ { \@@_mark:Nn #2 {right} - \@@_mark:Nn #2 {left} }
+ {
+ \skip_vertical:N \l_@@_rule_margin_dim
+ \tl_if_empty:NF { \l_@@_rule_code_tl } {
+ \tl_use:N \l_@@_rule_code_tl
+ \skip_vertical:N \l_@@_rule_margin_dim
+ }
+ }
+ \@@_vcenter:N #1
+% \end{macrocode}
+% Append the left label.
+% \begin{macrocode}
+ \tl_if_blank:VF \l_@@_left_label_tl {
+ \@@_make_simple:Nn #3 {
+ \box_move_down:nn { \l_@@_label_axis_dim } { \hbox:n {
+ \cs_set_eq:NN \inserttext \l_@@_left_label_tl
+ \tl_use:N \l_@@_left_label_template_tl
+ } }
+ }
+ \box_set_ht:cn { \@@_box:N #3 } { 0pt }
+ \box_set_dp:cn { \@@_box:N #3 } { 0pt }
+ \@@_append_left:NnN
+ \l_@@_c_box \l_@@_label_separation_dim \l_@@_d_box
+ }
+% \end{macrocode}
+% Append the right label.
+% \begin{macrocode}
+ \tl_if_blank:VF \l_@@_right_label_tl {
+ \@@_make_simple:Nn #3 {
+ \box_move_down:nn { \l_@@_label_axis_dim } { \hbox:n {
+ \cs_set_eq:NN \inserttext \l_@@_right_label_tl
+ \tl_use:N \l_@@_right_label_template_tl
+ } }
+ }
+ \box_set_ht:cn { \@@_box:N #3 } { 0pt }
+ \box_set_dp:cn { \@@_box:N #3 } { 0pt }
+ \@@_append_right:NnN
+ \l_@@_c_box \l_@@_label_separation_dim \l_@@_d_box
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \subsection{Stack-based interface}
+%
+% \subsubsection{The stack}
+%
+% Logically, box structures are stored on a stack. However, \TeX\ does not
+% provide data structures for that and the grouping mechanism is not flexible
+% enough, so we encode them using what we actually have. A stack for boxes is
+% implemented using a global hbox \cs{g_@@_stack_box} that contains all the
+% boxes successively. A sequence \cs{g_@@_stack_seq} is used to store the
+% dimensions property lists textually. We maintain a counter
+% \cs{g_@@_level_int} with the number of elements on the stack, for
+% consistency checks.
+% \begin{macrocode}
+\int_new:N \g_@@_level_int
+\box_new:N \g_@@_stack_box
+\seq_new:N \g_@@_stack_seq
+% \end{macrocode}
+%
+% \begin{macro}{\@@_clear_stack:}
+% Clear the stack.
+% \begin{macrocode}
+\cs_new:Nn \@@_clear_stack: {
+ \int_gset:Nn \g_@@_level_int { 0 }
+ \hbox_gset:Nn \g_@@_stack_box { }
+ \seq_gclear:N \g_@@_stack_seq
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_push:N}
+% Push the contents of a register on the stack.
+% \begin{macrocode}
+\cs_new:Nn \@@_push:N {
+ \int_gincr:N \g_@@_level_int
+ \hbox_gset:Nn \g_@@_stack_box
+ { \hbox_unpack:N \g_@@_stack_box \box_use:c { \@@_box:N #1 } }
+ \seq_gput_left:Nv \g_@@_stack_seq
+ { \@@_marks:N #1 }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_pop:N}
+% Pop the value from the top of the stack into a register.
+% \begin{macrocode}
+\cs_new:Nn \@@_pop:N {
+ \int_compare:nNnTF { \g_@@_level_int } > { 0 } {
+ \int_gdecr:N \g_@@_level_int
+ \hbox_gset:Nn \g_@@_stack_box {
+ \hbox_unpack:N \g_@@_stack_box
+ \box_gset_to_last:N \g_tmpa_box
+ }
+ \box_set_eq_clear:cN { \@@_box:N #1 } \g_tmpa_box
+ \seq_gpop_left:NN \g_@@_stack_seq \l_tmpa_tl
+ \tl_set_eq:cN { \@@_marks:N #1 } \l_tmpa_tl
+ } {
+ \PackageError{ebproof}{Missing~premiss~in~a~proof~tree}{}
+ \@@_clear:N #1
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Assembling trees}
+%
+% \begin{macrocode}
+\@@_new:N \l_@@_a_box
+\@@_new:N \l_@@_b_box
+\@@_new:N \l_@@_c_box
+\@@_new:N \l_@@_d_box
+% \end{macrocode}
+%
+% \begin{macro}{\@@_join_horizontal:n}
+% Join horizontally a number of elements at the top of the stack. If several
+% trees are joined, use the left mark of the left tree, the right mark of
+% the right tree and set the axis in the middle of these marks.
+% \begin{macrocode}
+\cs_new:Nn \@@_join_horizontal:n {
+ \int_case:nnF { #1 } {
+ { 0 } {
+ \group_begin:
+ \@@_clear:N \l_@@_a_box
+ \@@_push:N \l_@@_a_box
+ \group_end:
+ }
+ { 1 } { }
+ } {
+ \group_begin:
+ \@@_pop:N \l_@@_a_box
+ \prg_replicate:nn { #1 - 1 } {
+ \@@_pop:N \l_@@_b_box
+ \@@_append_left:NnN
+ \l_@@_a_box \l_@@_separation_dim \l_@@_b_box
+ }
+ \@@_set_mark:Nnn \l_@@_a_box { left }
+ { \@@_mark:Nn \l_@@_b_box { left } }
+ \@@_set_mark:Nnn \l_@@_a_box { axis }
+ { ( \@@_mark:Nn \l_@@_a_box { left }
+ + \@@_mark:Nn \l_@@_a_box { right } ) / 2 }
+ \@@_push:N \l_@@_a_box
+ \group_end:
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_join_vertical:}
+% Join vertically the two elements at the top of the stack, with a
+% horizontal rule of the appropriate size.
+% \begin{macrocode}
+\cs_new:Nn \@@_join_vertical: {
+ \group_begin:
+ \@@_pop:N \l_@@_a_box
+ \@@_pop:N \l_@@_b_box
+ \@@_enlarge_conclusion:NN \l_@@_b_box \l_@@_a_box
+ \@@_make_rule_for:NNN \l_@@_c_box \l_@@_b_box
+ \l_@@_d_box
+ \@@_append_vertical:NN \l_@@_a_box \l_@@_c_box
+ \@@_append_vertical:NN \l_@@_a_box \l_@@_b_box
+ \@@_push:N \l_@@_a_box
+ \group_end:
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{High-level commands}
+%
+% \begin{macro}{\@@_statement_parse:w}
+% An auxiliary function for parsing the argument in
+% \cs{@@_push_statement:n}.
+% \begin{macrocode}
+\cs_new:Npn \@@_statement_parse:w #1 & #2 & #3 \q_stop {
+ \tl_if_empty:nTF { #3 } {
+ \@@_make_simple:Nn \l_@@_a_box
+ { \cs_set:Npn \inserttext { #1 } \tl_use:N \l_@@_template_tl }
+ } {
+ \@@_make_split:Nnn \l_@@_a_box
+ { \cs_set:Npn \inserttext { #1 } \tl_use:N \l_@@_left_template_tl }
+ { \cs_set:Npn \inserttext { #2 } \tl_use:N \l_@@_right_template_tl }
+ }
+ \@@_push:N \l_@@_a_box
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_push_statement:n}
+% Push a box with default formatting, using explicit alignment if the code
+% contains a |&| character
+% \begin{macrocode}
+\cs_new:Nn \@@_push_statement:n {
+ \@@_statement_parse:w #1 & & \q_stop
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \subsection{Document interface}
+%
+% \subsubsection{Functions to define statements}
+%
+% The \cs{g_@@_statements_seq} variable contains the list of all defined
+% statements. For each statement |X|, there is a document command \cs{ebproofX}
+% and the alias \cs{X} is defined when entering a |prooftree| environment.
+% \begin{macrocode}
+\seq_new:N \g_@@_statements_seq
+% \end{macrocode}
+%
+% \begin{macro}{\@@_setup_statements:}
+% Install the aliases for statements, saving the original value of the control
+% sequences.
+% \begin{macrocode}
+\cs_new:Nn \@@_setup_statements: {
+ \seq_map_inline:Nn \g_@@_statements_seq {
+ \cs_set_eq:cc { ebproof_saved_ ##1 } { ##1 }
+ \cs_set_eq:cc { ##1 } { ebproof ##1 }
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_restore_statements:}
+% Restore the saved meanings of the control sequences. This is useful when
+% interpreting user-provided code in statement arguments. The meanings are
+% automatically restored when leaving a |prooftree| environment because of
+% grouping.
+% \begin{macrocode}
+\cs_new:Nn \@@_restore_statements: {
+ \seq_map_inline:Nn \g_@@_statements_seq {
+ \cs_set_eq:cc { ##1 } { ebproof_saved_ ##1 }
+ }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_new_statement:nnn}
+% Define a new statement. The first argument is the name, the second one is
+% an argument specifier as used by |xparse| and the third one is the body of
+% the command.
+% \begin{macrocode}
+\cs_new:Nn \@@_new_statement:nnn {
+ \exp_args:Nc \NewDocumentCommand { ebproof#1 }{ #2 } { #3 }
+ \seq_put_right:Nn \g_@@_statements_seq { #1 }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_new_deprecated_statement:nnnn}
+% Define a deprecated statement. The syntax is the same as above except that
+% an extra argument in third position indicates what should be used instead.
+% The effect is the same except that a warning message is issued the first
+% time the statement is used.
+% \begin{macrocode}
+\cs_new:Nn \@@_new_deprecated_statement:nnnn {
+ \cs_new:cpn { ebproof_#1_warning: } {
+ \PackageWarning { ebproof } { \token_to_str:c{#1}~is~deprecated,~#3 }
+ \cs_gset:cn { ebproof_#1_warning: } { }
+ }
+ \@@_new_statement:nnn { #1 } { #2 }
+ { \use:c { ebproof_#1_warning: } #4 }
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \subsubsection{Basic commands}
+%
+% \begin{macro}{\ebproofset,\set}
+% This is a simple wrapper around \cs{keys_set:nn}.
+% \begin{macrocode}
+\@@_new_statement:nnn { set } { m } {
+ \keys_set:nn { ebproof } { #1 }
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\hypo}
+% This is mostly a wrapper around \cs{ebproof_push_statement:n}, with
+% material to handle options and the statements macros.
+% \begin{macrocode}
+\@@_new_statement:nnn { hypo } { O{} m } {
+ \group_begin:
+ \@@_restore_statements:
+ \keys_set:nn { ebproof } { #1 }
+ \@@_push_statement:n { #2 }
+ \group_end:
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\infer}
+% This is a bit more involved than \cs{hypo} because we have to handle rule
+% style options and joining.
+% \begin{macrocode}
+\@@_new_statement:nnn { infer } { O{} m O{} m } {
+ \group_begin:
+ \@@_restore_statements:
+ \keys_set_known:nnN { ebproof / rule~style } { #1 } \l_tmpa_tl
+ \keys_set:nV { ebproof } \l_tmpa_tl
+ \tl_set:Nn \l_@@_right_label_tl { #3 }
+ \@@_join_horizontal:n { #2 }
+ \@@_push_statement:n { #4 }
+ \@@_join_vertical:
+ \group_end:
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\ellipsis}
+% An ellipsis is made by hand using vertical leaders to render the dots
+% after rendering the label.
+% \begin{macrocode}
+\@@_new_statement:nnn { ellipsis } { m m } {
+ \group_begin:
+ \@@_restore_statements:
+ \tl_clear:N \l_@@_rule_code_tl
+ \@@_make_split:Nnn \l_@@_a_box { } {
+ \vbox_set:Nn \l_tmpa_box {
+ \skip_vertical:n { 1.2ex }
+ \hbox:n { \tex_ignorespaces:D #1 }
+ \skip_vertical:n { 1.2ex }
+ }
+ \vbox_to_ht:nn { \box_ht:N \l_tmpa_box } {
+ \tex_xleaders:D \vbox_to_ht:nn { .8ex }
+ { \tex_vss:D \hbox:n { . } \tex_vss:D }
+ \tex_vfill:D
+ }
+ \hbox_overlap_right:n { ~ \box_use:N \l_tmpa_box }
+ }
+ \@@_push:N \l_@@_a_box
+ \@@_join_vertical:
+ \@@_push_statement:n {#2}
+ \@@_join_vertical:
+ \group_end:
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Modifying trees}
+%
+% \begin{macro}{\rewrite}
+% Rewrite the box at the top of the stack while preserving its dimensions an
+% marks. The code is typeset in horizontal mode, with control sequences to
+% access the original box and its marks.
+% \begin{macrocode}
+\@@_new_statement:nnn { rewrite } { m } {
+ \group_begin:
+ \@@_restore_statements:
+ \@@_pop:N \l_@@_a_box
+ \box_set_eq:Nc \l_tmpa_box { \@@_box:N \l_@@_a_box }
+ \hbox_set:Nn \l_tmpb_box {
+ \cs_set_eq:NN \treebox \l_tmpa_box
+ \cs_set:Npn \treemark { \@@_mark:Nn \l_@@_a_box }
+ { #1 }
+ }
+ \box_set_wd:Nn \l_tmpb_box { \box_wd:c { \@@_box:N \l_@@_a_box } }
+ \box_set_ht:Nn \l_tmpb_box { \box_ht:c { \@@_box:N \l_@@_a_box } }
+ \box_set_dp:Nn \l_tmpb_box { \box_dp:c { \@@_box:N \l_@@_a_box } }
+ \box_set_eq:cN { \@@_box:N \l_@@_a_box } \l_tmpb_box
+ \@@_push:N \l_@@_a_box
+ \group_end:
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\delims}
+% Insert \cs{left} and \cs{right} delimiters without changing the alignment.
+% \begin{macrocode}
+\@@_new_statement:nnn { delims } { m m } {
+ \group_begin:
+ \@@_restore_statements:
+ \@@_pop:N \l_@@_a_box
+ \hbox_set:Nn \l_tmpa_box
+ { $ \tex_vcenter:D { \box_use:c { \@@_box:N \l_@@_a_box } } $ }
+ \dim_set:Nn \l_tmpa_dim
+ { \box_ht:N \l_tmpa_box - \box_ht:c { \@@_box:N \l_@@_a_box } }
+ \hbox_set:cn { \@@_box:N \l_@@_a_box } {
+ $ #1 \tex_vrule:D
+ height \box_ht:N \l_tmpa_box depth \box_dp:N \l_tmpa_box width 0pt
+ \tex_right:D . $
+ }
+ \@@_shift_x:Nn \l_@@_a_box
+ { \box_wd:c { \@@_box:N \l_@@_a_box } }
+ \hbox_set:cn { \@@_box:N \l_@@_a_box } {
+ \hbox_unpack:c { \@@_box:N \l_@@_a_box }
+ $ \tex_left:D . \box_use:N \l_tmpa_box #2 $
+ }
+ \hbox_set:cn { \@@_box:N \l_@@_a_box }
+ { \box_move_down:nn { \l_tmpa_dim }
+ { \box_use:c { \@@_box:N \l_@@_a_box } } }
+ \@@_push:N \l_@@_a_box
+ \group_end:
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\overlay}
+% Pop two trees and append the second tree as an overlay over the first one,
+% so that the baselines and axes match. The bounding box of the result
+% adjusts to contain both trees.
+% \begin{macrocode}
+\@@_new_statement:nnn { overlay } { } {
+ \group_begin:
+ \@@_pop:N \l_@@_a_box
+ \@@_pop:N \l_@@_b_box
+ \@@_overlay:NN \l_@@_a_box \l_@@_b_box
+ \@@_push:N \l_@@_a_box
+ \group_end:
+}
+% \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Deprecated statements}
+%
+% These statements were defined in versions 1.x of the package, they are
+% preserved for temporary upwards compatibility and will be removed in a
+% future version.
+% \begin{macrocode}
+\@@_new_deprecated_statement:nnnn { Alter } { m }
+ { use~\token_to_str:c{rewrite}~instead } { \ebproofrewrite{ #1 \box\treebox } }
+\@@_new_deprecated_statement:nnnn { Delims } { }
+ { use~\token_to_str:c{delims}~instead } { \ebproofdelims }
+\@@_new_deprecated_statement:nnnn { Ellipsis } { }
+ { use~\token_to_str:c{ellipsis}~instead } { \ebproofellipsis }
+\@@_new_deprecated_statement:nnnn { Hypo } { }
+ { use~\token_to_str:c{hypo}~instead } { \ebproofhypo }
+\@@_new_deprecated_statement:nnnn { Infer } { }
+ { use~\token_to_str:c{infer}~instead } { \ebproofinfer }
+% \end{macrocode}
+%
+%
+% \subsubsection{Environment interface}
+%
+% The stack is initialised globally. The \env{prooftree} environment does not
+% clear the stack, instead it saves the initial level in order to check that
+% statements are properly balanced. This allows for nested uses of the
+% environment, if it ever happens to be useful.
+%
+% \begin{macrocode}
+\@@_clear_stack:
+\tl_new:N \l_@@_start_level_tl
+% \end{macrocode}
+%
+% \begin{macro}{prooftree,prooftree*}
+% The \env{prooftree} environment.
+% \begin{macrocode}
+\NewDocumentEnvironment { prooftree } { s O{} } {
+ \group_align_safe_begin:
+ \keys_set_known:nnN { ebproof / proof~style } { #2 } \l_tmpa_tl
+ \keys_set:nV { ebproof } \l_tmpa_tl
+ \tl_set:Nx \l_@@_start_level_tl { \int_use:N \g_@@_level_int }
+ \vbox_set:Nw \l_tmpa_box
+ \@@_setup_statements:
+} {
+ \vbox_set_end:
+ \@@_pop:N \l_@@_a_box
+ \int_compare:nNnF { \g_@@_level_int } = { \tl_use:N \l_@@_start_level_tl } {
+ \PackageError{ebproof}{Malformed~proof~tree}{
+ Some~hypotheses~were~declared~but~not~used~in~this~tree.}
+ }
+ \IfBooleanTF { #1 } {
+ \[ \box_use:c { \@@_box:N \l_@@_a_box } \]
+ \ignorespacesafterend
+ } {
+ \hbox_unpack:N \c_empty_box
+ \bool_if:NTF \l_@@_center_bool {
+ \hbox:n { $ \tex_vcenter:D { \box_use:c { \@@_box:N \l_@@_a_box } } $ }
+ } {
+ \box_use:c { \@@_box:N \l_@@_a_box }
+ }
+ }
+ \group_align_safe_end:
+}
+% \end{macrocode}
+% A trick for the starred version:
+% \begin{macrocode}
+\cs_new:cpn { prooftree* } { \prooftree* }
+\cs_new:cpn { endprooftree* } { \endprooftree }
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macrocode}
+%</package>
+% \end{macrocode}
+%
+% \end{implementation}