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Code Editor : bussproofs.sty

%
\def\BPmessage{Proof Tree (bussproofs) style macros. Version 1.0.}
% bussproofs.sty.  Version 1.0
%     (c) 1994,1995,1996,2004,2005,2006. Copyright retained by Samuel R. Buss.
%
% ==== Legal statement: ====
% 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
%  http://www.latex-project.org/lppl.txt.
% and version 1.3 or later is part of all distributions of LaTeX
% version 2005/12/1 or later.
%
% This work has the LPPL maintenance status 'maintained'.
%
% The Current Maintainer of the work is Sam Buss.
% 
% This work consists of bussproofs.sty.
%  =====
% Informal summary of legal situation:
%     This software may be used and distributed freely, except that
%     if you make changes, you must change the file name to be different
%     than bussproofs.sty to avoid compatibility problems.
% The terms of the LaTeX Public License are the legally controlling terms
%     and override any contradictory terms of the "informal situation".
%
%     Please report comments and bugs to sbuss@ucsd.edu.
%
%  Thanks to Felix Joachimski for making changes to let these macros
%   work in plain TeX in addition to LaTeX.  Nothing has been done
%   to see if they work in AMSTeX.  The comments below mostly
%   are written for LaTeX, however.
%  July 2004, version 0.7
%       - bug fix, right labels with descenders inserted too much space.
%         Thanks to Peter Smith for finding this bug,
%     see http://www.phil.cam.ac.uk/teaching_staff/Smith/LaTeX/
%  March 2005, version 0.8.
%   Added a default definition for \fCenter at Denis Kosygin's
%   suggestion.
%  September 2005, version 0.9.
%       Fixed some subtle spacing problems, by adding %'s to the end of
%   few lines where they were inadvertantly omitted.  Thanks to
%   Arnold Beckmann for finding and fixing this problem.
%  April 2006, version 0.9.1.  Updated comments and testbp2.tex file.
%       No change to the actual macros.
%  June 2006, version 1.0.  The first integer numbered release.
%       New feature: root of proof may now be at the bottom instead of
%       at just the top.  Thanks to Alex Hertel for the suggestion to implement
%       this.

% A good exposition of how to use bussproofs.sty (version 0.9) has been written
%  by Peter Smith and is available on the internet.
% The comments below also describe the features of bussproofs.sty,
%  including user-modifiable parameters.

%  bussproofs.sty allows the construction of proof trees in the
%     style of the sequent calculus and many other proof systems
%     One novel feature of these macros is they support the horizontal
%     alignment according to some center point specified with the
%     command \fCenter.  This is the style often used in sequent
%     calculus proofs.
%     Proofs are specified in left-to-right traversal order.
%       For example a proof
%               A   B
%                               -----
%                          D      C
%                         ---------
%                             E
%
%     if given in the order D,A,B,C,E.  Each line in the proof is
%     specified according to the arity of the inference which generates
%     it.  Thus, E would be specified with a \BinaryInf  or  \BinaryInfC
%     command.
%
%     The above proof tree could be displayed with the commands:
%
%               \AxiomC{D}
%               \AxiomC{A}
%               \AxiomC{B}
%               \BinaryInfC{C}
%               \BinaryInfC{E}
%               \DisplayProof
%
%     Inferences in a proof may be nullary (axioms), unary, binary, or
%     trinary.
%
%     IMPORTANT:  You must give the \DisplayProof command to make the proof
%      be printed.  To display a centered proof on a line by itself,
%      put the proof inside \begin{center} ... \end{center}.
%
%     There are two styles for specifying horizontal centering of
%     lines (formulas or sequents) in a proof.  One format \AxiomC{...}
%     just centers the formula {...} in the usual way.  The other
%     format is \Axiom$...\fCenter...$.  Here,  the \fCenter specifies
%     the center of the formula.  (It is permissable for \fCenter to
%     generate typeset material; in fact, I usually define it to generate
%     the sequent arrow.)  In unary inferences, the \fCenter
%     positions will be vertically aligned in the upper and lower lines of
%     the inference.  Unary, Binary, Trinary inferences are specified
%     with the same format as Axioms.  The two styles of centering
%     lines may be combined in a single proof.
%
%     By using the optional \EnableBpAbbreviations command, various
%   abbreviated two letter commands are enabled.  This allows
%   \AX and \AXC for \Axiom and \AxiomC, (resp.),
%   \DP for \DisplayProof,
%   \BI and \BIC for \BinaryInf and \BinaryInfC,
%   \UI and \UIC for \UnaryInf  and \UnaryInfC,
%   \TI and \TIC for \TrinaryInf and \TrinaryInfC,
%   \LL and \RL for \LeftLabel and \RightLabel.
%     The enabling of these short abbreviations is OPTIONAL, since
%       there is the possibility of conflicting with names from other
%       macro packages.
%
%     By default, the inferences have single horizontal lines (scores)
%       This can be overridden using the \doubleLine, \noLine commands.
%       These two commands affect only the next inference.  You can make
%   make a permanent override that applies to the rest of the current
%       proof using \alwaysDoubleLine and \alwaysNoLine.  \singleLine
%   and \alwaysSingleLine work in the analogous way.
%
%     The macros do their best to give good placements of for the
%     parts of the proof.  Several macros allow you to override the
%     defaults.  These are \insertBetweenHyps{...} which overrides
%     the default spacing between hypotheses of Binary and Trinary
%     inferences with {...}.  And \kernHyps{...} specifies a distance
%     to shift the whole block of hypotheses to the right (modifying
%     the default center position.
%       Other macros set the vertical placement of the whole proof.
%     The default is to try to do a good job of placement for inferences
%     included in text.  Two other useful macros are: \bottomAlignProof
%     which aligns the hbox output by \DisplayProof according to the base
%     of the bottom line of the proof, and \centerAlignProof which
%     does a precise center vertical alignment.
%
%     Often, one wishes to place a label next to an inference, usually
%   to specify the type of inference.  These labels can be placed
%       by using the commands \LeftLabel{...} and \RightLabel{...}
%       immediately before the command which specifies the inference.
%       For example, to generate
%
%                       A     B
%                      --------- X
%                          C
%
%       use the commands  
%             \AxiomC{A}
%             \AxiomC{B}
%             \RightLabel{X}
%             \BinaryInfC{C}
%             \DisplayProof
%
%     The \DisplayProof command just displays the proof as a text
%   item.  This allows you to put proofs anywhere normal text
%   might appear; for example, in a paragraph, in a table, in
%   a tabbing environment, etc.  When displaying a proof as inline text,
%   you should write \DisplayProof{}  (with curly brackets) so that
%   LaTeX will not "eat" the white space following the \DisplayProof
%   command.
%     For displaying proofs in a centered display:  Do not use the \[...\]
%   construction (nor $$...$$).  Instead use
%   \begin{center} ... \DisplayProof\end{center}.
%     Actually there is a better construction to use instead of the
%   \begin{center}...\DisplayProof\end{center}.  This is to
%   write
%       \begin{prooftree} ... \end{prooftree}.
%       Note there is no \DisplayProof used for this: the
%   \end{prooftree} automatically supplies the \DisplayProof
%   command.
%
%     Warning: Any commands that set line types or set vertical or
%   horizontal alignment that are given AFTER the \DisplayProof
%   command will affect the next proof, no matter how distant.

% Usages:
% =======
%
%   \Axiom$<antecedent>\fCenter<succedent>$
%
%   \AxiomC{<whole sequent or formula}
%
%   Note that the use of surrounding {}'s is mandatory in \AxiomC and
%   is prohibited in $\Axiom.  On the other hand, the $'s are optional
%   in \AxiomC and are mandatory in \Axiom.  To typeset the argument
%   to \AxiomC in math mode, you must use $'s (or $...$ ).
%
%   \UnaryInf$<antecendent>\fCenter<succedent>$
%
%   \UnaryInfC{<whole sequent or formula>}
%
%   \BinaryInf$<antecendent>\fCenter<succedent>$
%
%   \BinaryInfC{<whole sequent or formula>}
%
%   \TrinaryInf$<antecendent>\fCenter<succedent>$
%
%   \TrinaryInfC{<whole sequent or formula>}
%
%   \LeftLabel{<text>} - Puts <text> as a label to the left
%             of the next inference line.  (Works even if
%             \noLine is used too.)
%
%   \RightLabel{<text>} - Puts <text> as a label to the right of the
%             next inference line.  (Also works with \noLine.)
%
%   \DisplayProof - outputs the whole proof tree (and finishes it).
%           The proof tree is output as an hbox.
%
%
%   \kernHyps{<dimen>}  - Slides the upper hypotheses right distance <dimen>
%             (This is similar to shifting conclusion left)
%           - kernHyps works with Unary, Binary and Trinary
%             inferences and with centered or uncentered sequents.
%           - Negative values for <dimen> are permitted.
%
%   \insertBetweenHyps{...} - {...} will be inserted between the upper
%             hypotheses of a Binary or Trinary Inferences.
%                         It is possible to use negative horizontal space
%                 to push them closer together (and even overlap).
%             This command affects only the next inference.
%
%   \doubleLine         - Makes the current (ie, next) horizontal line doubled
%
%   \alwaysDoubleLine   - Makes lines doubled for rest of proof
%
%   \singleLine     - Makes the current (ie, next) line single
%
%   \alwaysSingleLine   - Undoes \alwaysDoubleLine or \alwaysNoLine.
%
%   \noLine     - Make no line at all at current (ie next) inference.
%
%   \alwaysNoLine       - Makes no lines for rest of proof. (Untested)
%
%   \solidLine      - Does solid horizontal line for current inference
%
%   \dottedLine     - Does dotted horizontal line for current inference
%
%   \dashedLine     - Does dashed horizontal line for current inference
%
%   \alwaysSolidLine    - Makes the indicated change in line type, permanently
%   \alwaysDashedLine       until end of proof or until overridden.
%   \alwaysDottedLine
%
%   \bottomAlignProof   - Vertically align proof according to its bottom line.
%   \centerAlignProof   - Vertically align proof proof precisely in its center.
%   \normalAlignProof   - Overrides earlier bottom/center AlignProof commands.
%             The default alignment will look good in most cases,
%               whether the proof is displayed or is
%               in-line.  Other alignments may be more
%               appropriate when putting proofs in tables or
%               pictures, etc.  For custom alignments, use
%               TeX's raise commands.
%
%   \rootAtTop  - specifies that proofs have their root a the top.  That it,
%                 proofs will be "upside down".
%   \rootAtBottom - (default) Specifies that proofs have root at the bottom
%         The \rootAtTop and \rootAtBottom commands apply *only* to the
%         current proof.  If you want to make them persistent, use one of
%         the next two commands:
%   \alwaysRootAtTop
%   \alwaysRootAtBottom (default)
%

% Optional short abbreviations for commands:
\def\EnableBpAbbreviations{%
    \let\AX\Axiom
    \let\AXC\AxiomC
    \let\UI\UnaryInf
    \let\UIC\UnaryInfC
    \let\BI\BinaryInf
    \let\BIC\BinaryInfC
    \let\TI\TrinaryInf
    \let\TIC\TrinaryInfC
    \let\LL\LeftLabel
    \let\RL\RightLabel
    \let\DP\DisplayProof
}

% Parameters which control the style of the proof trees.
% The user may wish to override these parameters locally or globally.
%   BUT DON'T CHANGE THE PARAMETERS BY CHANGING THIS FILE (to avoid
%   future incompatibilities).  Instead, you should change them in your
%   TeX document right after including this style file in the 
%   header material of your LaTeX document.

\def\ScoreOverhang{4pt}         % How much underlines extend out
\def\ScoreOverhangLeft{\ScoreOverhang}
\def\ScoreOverhangRight{\ScoreOverhang}

\def\extraVskip{2pt}            % Extra space above and below lines
\def\ruleScoreFiller{\hrule}        % Horizontal rule filler.
\def\dottedScoreFiller{\hbox to4pt{\hss.\hss}}
\def\dashedScoreFiller{\hbox to2.8mm{\hss\vrule width1.4mm height0.4pt depth0.0pt\hss}}
\def\defaultScoreFiller{\ruleScoreFiller}  % Default horizontal filler.
\def\defaultBuildScore{\buildSingleScore}  % In \singleLine mode at start.

\def\defaultHypSeparation{\hskip.2in}   % Used if \insertBetweenHyps isn't given

\def\labelSpacing{3pt}      % Horizontal space separating labels and lines

\def\proofSkipAmount{\vskip.8ex plus.8ex minus.4ex}
            % Space above and below a prooftree display.

\def\defaultRootPosition{\buildRootBottom} % Default: Proofs root at bottom
%\def\defaultRootPosition{\buildRootTop}  % Makes all proofs upside down

\ifx\fCenter\undefined
\def\fCenter{\relax}
\fi

%
% End of user-modifiable parameters.
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Here are some internal paramenters and defaults.  Not really intended
%  to be user-modifiable.

\def\theHypSeparation{\defaultHypSeparation}
\def\alwaysScoreFiller{\defaultScoreFiller} % Horizontal filler.
\def\alwaysBuildScore{\defaultBuildScore}
\def\theScoreFiller{\alwaysScoreFiller} % Horizontal filler.
\def\buildScore{\alwaysBuildScore}   %This command builds the score.
\def\hypKernAmt{0pt}    % Initial setting for kerning the hypotheses.

\def\defaultLeftLabel{}
\def\defaultRightLabel{}

\def\myTrue{Y}
\def\bottomAlignFlag{N}
\def\centerAlignFlag{N}
\def\defaultRootAtBottomFlag{Y}
\def\rootAtBottomFlag{Y}

% End of internal parameters and defaults.

\expandafter\ifx\csname newenvironment\endcsname\relax%
% If in TeX:
\message{\BPmessage}
\def\makeatletter{\catcode`\@=11\relax}
\def\makeatother{\catcode`\@=12\relax}
\makeatletter
\def\newcount{\alloc@0\count\countdef\insc@unt}
\def\newdimen{\alloc@1\dimen\dimendef\insc@unt}
\def\newskip{\alloc@2\skip\skipdef\insc@unt}
\def\newbox{\alloc@4\box\chardef\insc@unt}
\makeatother
\else
% If in LaTeX
\typeout{\BPmessage}
\newenvironment{prooftree}%
{\begin{center}\proofSkipAmount \leavevmode}%
{\DisplayProof \proofSkipAmount \end{center} }
\fi

\def\thecur#1{\csname#1\number\theLevel\endcsname}

\newcount\theLevel    % This counter is the height of the stack.
\global\theLevel=0      % Initialized to zero
\newcount\myMaxLevel
\global\myMaxLevel=0
\newbox\myBoxA      % Temporary storage boxes
\newbox\myBoxB
\newbox\myBoxC
\newbox\myBoxD
\newbox\myBoxLL     % Boxes for the left label and the right label.
\newbox\myBoxRL
\newdimen\thisAboveSkip     %Internal use: amount to skip above line
\newdimen\thisBelowSkip     %Internal use: amount to skip below line
\newdimen\newScoreStart     % More temporary storage.
\newdimen\newScoreEnd
\newdimen\newCenter
\newdimen\displace
\newdimen\leftLowerAmt%     Amount to lower left label
\newdimen\rightLowerAmt%    Amount to lower right label
\newdimen\scoreHeight%      Score height
\newdimen\scoreDepth%       Score Depth
\newdimen\htLbox%
\newdimen\htRbox%
\newdimen\htAbox%
\newdimen\htCbox%

\setbox\myBoxLL=\hbox{\defaultLeftLabel}%
\setbox\myBoxRL=\hbox{\defaultRightLabel}%

\def\allocatemore{%
    \ifnum\theLevel>\myMaxLevel%
        \expandafter\newbox\curBox%
        \expandafter\newdimen\curScoreStart%
        \expandafter\newdimen\curCenter%
        \expandafter\newdimen\curScoreEnd%
        \global\advance\myMaxLevel by1%
    \fi%
}

\def\prepAxiom{%
    \advance\theLevel by1%
    \edef\curBox{\thecur{myBox}}%
    \edef\curScoreStart{\thecur{myScoreStart}}%
    \edef\curCenter{\thecur{myCenter}}%
    \edef\curScoreEnd{\thecur{myScoreEnd}}%
    \allocatemore%
}

\def\Axiom$#1\fCenter#2${%
    % Get level and correct names set.
    \prepAxiom%
    % Define the boxes
    \setbox\myBoxA=\hbox{$\mathord{#1}\fCenter\mathord{\relax}$}%
    \setbox\myBoxB=\hbox{$#2$}%
    \global\setbox\curBox=%
         \hbox{\hskip\ScoreOverhangLeft\relax%
        \unhcopy\myBoxA\unhcopy\myBoxB\hskip\ScoreOverhangRight\relax}%
    % Set the relevant dimensions for the boxes
    \global\curScoreStart=0pt \relax
    \global\curScoreEnd=\wd\curBox \relax
    \global\curCenter=\wd\myBoxA \relax
    \global\advance \curCenter by \ScoreOverhangLeft%
    \ignorespaces
}

\def\AxiomC#1{      % Note argument not in math mode
    % Get level and correct names set.
    \prepAxiom%
        % Define the box.
    \setbox\myBoxA=\hbox{#1}%
    \global\setbox\curBox =%
        \hbox{\hskip\ScoreOverhangLeft\relax%
                        \unhcopy\myBoxA\hskip\ScoreOverhangRight\relax}%
    % Set the relevant dimensions for the boxes
        \global\curScoreStart=0pt \relax
        \global\curScoreEnd=\wd\curBox \relax
        \global\curCenter=.5\wd\curBox \relax
        \global\advance \curCenter by \ScoreOverhangLeft%
    \ignorespaces
}

\def\prepUnary{%
    \ifnum \theLevel<1
        \errmessage{Hypotheses missing!}
    \fi%
    \edef\curBox{\thecur{myBox}}%
    \edef\curScoreStart{\thecur{myScoreStart}}%
    \edef\curCenter{\thecur{myCenter}}%
    \edef\curScoreEnd{\thecur{myScoreEnd}}%
}

\def\UnaryInf$#1\fCenter#2${%
    \prepUnary%
    \buildConclusion{#1}{#2}%
    \joinUnary%
    \resetInferenceDefaults%
    \ignorespaces%
}

\def\UnaryInfC#1{
    \prepUnary%
    \buildConclusionC{#1}%
    %Align and join the curBox and the new box into one vbox.
    \joinUnary%
    \resetInferenceDefaults%
    \ignorespaces%
}

\def\prepBinary{%
    \ifnum\theLevel<2
        \errmessage{Hypotheses missing!}
    \fi%
    \edef\rcurBox{\thecur{myBox}}%   Set up names of right hypothesis
    \edef\rcurScoreStart{\thecur{myScoreStart}}%
    \edef\rcurCenter{\thecur{myCenter}}%
    \edef\rcurScoreEnd{\thecur{myScoreEnd}}%
    \advance\theLevel by-1%
    \edef\lcurBox{\thecur{myBox}}% Set up names of left hypothesis
    \edef\lcurScoreStart{\thecur{myScoreStart}}%
    \edef\lcurCenter{\thecur{myCenter}}%
    \edef\lcurScoreEnd{\thecur{myScoreEnd}}%
}

\def\BinaryInf$#1\fCenter#2${%
    \prepBinary%
    \buildConclusion{#1}{#2}%
    \joinBinary%
    \resetInferenceDefaults%
    \ignorespaces%
}

\def\BinaryInfC#1{%
    \prepBinary%
    \buildConclusionC{#1}%
    \joinBinary%
    \resetInferenceDefaults%
    \ignorespaces%
}

\def\prepTrinary{%
    \ifnum\theLevel<3
        \errmessage{Hypotheses missing!}
    \fi%
    \edef\rcurBox{\thecur{myBox}}%   Set up names of right hypothesis
    \edef\rcurScoreStart{\thecur{myScoreStart}}%
    \edef\rcurCenter{\thecur{myCenter}}%
    \edef\rcurScoreEnd{\thecur{myScoreEnd}}%
    \advance\theLevel by-1%
    \edef\ccurBox{\thecur{myBox}}% Set up names of center hypothesis
    \edef\ccurScoreStart{\thecur{myScoreStart}}%
    \edef\ccurCenter{\thecur{myCenter}}%
    \edef\ccurScoreEnd{\thecur{myScoreEnd}}%
    \advance\theLevel by-1%
    \edef\lcurBox{\thecur{myBox}}% Set up names of left hypothesis
    \edef\lcurScoreStart{\thecur{myScoreStart}}%
    \edef\lcurCenter{\thecur{myCenter}}%
    \edef\lcurScoreEnd{\thecur{myScoreEnd}}%
}

\def\TrinaryInf$#1\fCenter#2${%
    \prepTrinary%
    \buildConclusion{#1}{#2}%
    \joinTrinary%
    \resetInferenceDefaults%
    \ignorespaces%
}

\def\TrinaryInfC#1{%
    \prepTrinary%
    \buildConclusionC{#1}%
    \joinTrinary%
    \resetInferenceDefaults%
    \ignorespaces%
}

\def\buildConclusion#1#2{% Build lower sequent w/ center at \fCenter position.
    % Define the boxes
        \setbox\myBoxA=\hbox{$\mathord{#1}\fCenter\mathord{\relax}$}%
        \setbox\myBoxB=\hbox{$#2$}%
    % Put them together in \myBoxC
    \setbox\myBoxC =%
          \hbox{\hskip\ScoreOverhangLeft\relax%
        \unhcopy\myBoxA\unhcopy\myBoxB\hskip\ScoreOverhangRight\relax}%
    % Calculate the center of the \myBoxC string.
    \newScoreStart=0pt \relax%
    \newCenter=\wd\myBoxA \relax%
    \advance \newCenter by \ScoreOverhangLeft%
    \newScoreEnd=\wd\myBoxC%
}

\def\buildConclusionC#1{% Build lower sequent w/o \fCenter present.
        % Define the box.
    \setbox\myBoxA=\hbox{#1}%
    \setbox\myBoxC =%
        \hbox{\hbox{\hskip\ScoreOverhangLeft\relax%
                        \unhcopy\myBoxA\hskip\ScoreOverhangRight\relax}}%
    % Calculate kerning to line up centers
    \newScoreStart=0pt \relax%
    \newCenter=.5\wd\myBoxC \relax%
    \newScoreEnd=\wd\myBoxC%
        \advance \newCenter by \ScoreOverhangLeft%
}

\def\joinUnary{%Align and join \curBox and \myBoxC into a single vbox
    \global\advance\curCenter by -\hypKernAmt%
    \ifnum\curCenter<\newCenter%
        \displace=\newCenter%
        \advance \displace by -\curCenter%
        \kernUpperBox%
    \else%
        \displace=\curCenter%
        \advance \displace by -\newCenter%
        \kernLowerBox%
    \fi%
        \ifnum \newScoreStart < \curScoreStart %
        \global \curScoreStart = \newScoreStart \fi%
    \ifnum \curScoreEnd < \newScoreEnd %
        \global \curScoreEnd = \newScoreEnd \fi%
    % Leave room for the left label.
    \ifnum \curScoreStart<\wd\myBoxLL%
        \global\displace = \wd\myBoxLL%
        \global\advance\displace by -\curScoreStart%
        \kernUpperBox%
        \kernLowerBox%
    \fi%
    % Draw the score
    \buildScore%
    % Form the score and labels into a box.
    \buildScoreLabels%
    % Form the new box and its dimensions
    \ifx\rootAtBottomFlag\myTrue%  
        \buildRootBottom%
    \else%
        \buildRootTop%
    \fi%
    \global \curScoreStart=\newScoreStart%
    \global \curScoreEnd=\newScoreEnd%
    \global \curCenter=\newCenter%
}

\def\buildRootBottom{%         
    \global \setbox \curBox =%
        \vbox{\box\curBox%
            \vskip\thisAboveSkip \relax%
            \nointerlineskip\box\myBoxD%
            \vskip\thisBelowSkip \relax%
            \nointerlineskip\box\myBoxC}%
}

\def\buildRootTop{%
    \global \setbox \curBox =%
        \vbox{\box\myBoxC%
            \vskip\thisAboveSkip \relax%
            \nointerlineskip\box\myBoxD%
            \vskip\thisBelowSkip \relax%
            \nointerlineskip\box\curBox}%
}

\def\kernUpperBox{%
        \global\setbox\curBox =%
            \hbox{\hskip\displace\box\curBox}%
        \global\advance \curScoreStart by \displace%
        \global\advance \curScoreEnd by \displace%
        \global\advance\curCenter by \displace%
}

\def\kernLowerBox{%
        \global\setbox\myBoxC =%
            \hbox{\hskip\displace\unhbox\myBoxC}%
        \global\advance \newScoreStart by \displace%
        \global\advance \newScoreEnd by \displace%
        \global\advance\newCenter by \displace%
}

\def\joinBinary{% Construct the binary inference into a vbox.
    % Join the two hypotheses's boxes into one hbox.
    \setbox\myBoxA=\hbox{\theHypSeparation}%
    \lcurScoreEnd=\rcurScoreEnd%
    \advance\lcurScoreEnd by\wd\lcurBox%
    \advance\lcurScoreEnd by\wd\myBoxA%
    \displace=\lcurScoreEnd%
    \advance\displace by -\lcurScoreStart%
    \lcurCenter=.5\displace%
    \advance\lcurCenter by\lcurScoreStart%
    \ifx\rootAtBottomFlag\myTrue%
        \setbox\lcurBox=%
            \hbox{\box\lcurBox\unhcopy\myBoxA\box\rcurBox}%
    \else%
        \htLbox = \ht\lcurBox%
        \htAbox = \ht\myBoxA%
        \htRbox = \ht\rcurBox%
        \setbox\lcurBox=%
            \hbox{\lower\htLbox\box\lcurBox%
                  \lower\htAbox\box\myBoxA\lower\htRbox\box\rcurBox}%
    \fi%
    % Adjust center of upper hypotheses according to how much
    %   the lower sequent is off-center.
    \displace=\newCenter%
    \advance\displace by -.5\newScoreStart%
    \advance\displace by -.5\newScoreEnd%
    \advance\lcurCenter by \displace%
    %Align and join the curBox and the two hypotheses's box into one vbox.
    \edef\curBox{\lcurBox}%
    \edef\curScoreStart{\lcurScoreStart}%
    \edef\curScoreEnd{\lcurScoreEnd}%
    \edef\curCenter{\lcurCenter}%
    \joinUnary%
}

\def\joinTrinary{% Construct the trinary inference into a vbox.
    % Join the three hypotheses's boxes into one hbox.
    \setbox\myBoxA=\hbox{\theHypSeparation}%
    \lcurScoreEnd=\rcurScoreEnd%
    \advance\lcurScoreEnd by\wd\lcurBox%
    \advance\lcurScoreEnd by\wd\ccurBox%
    \advance\lcurScoreEnd by2\wd\myBoxA%
    \displace=\lcurScoreEnd%
    \advance\displace by -\lcurScoreStart%
    \lcurCenter=.5\displace%
    \advance\lcurCenter by\lcurScoreStart%
    \ifx\rootAtBottomFlag\myTrue%
        \setbox\lcurBox=%
            \hbox{\box\lcurBox\unhcopy\myBoxA\box\ccurBox%
                      \unhcopy\myBoxA\box\rcurBox}%
    \else%
        \htLbox = \ht\lcurBox%
        \htAbox = \ht\myBoxA%
        \htCbox = \ht\ccurBox%
        \htRbox = \ht\rcurBox%
        \setbox\lcurBox=%
            \hbox{\lower\htLbox\box\lcurBox%
                  \lower\htAbox\box\myBoxA\lower\htCbox\box\ccurBox%
                  \lower\htAbox\box\myBoxA\lower\htRbox\box\rcurBox}%
    \fi%
    % Adjust center of upper hypotheses according to how much
    %   the lower sequent is off-center.
    \displace=\newCenter%
    \advance\displace by -.5\newScoreStart%
    \advance\displace by -.5\newScoreEnd%
    \advance\lcurCenter by \displace%
    %Align and join the curBox and the two hypotheses's box into one vbox.
    \edef\curBox{\lcurBox}%
    \edef\curScoreStart{\lcurScoreStart}%
    \edef\curScoreEnd{\lcurScoreEnd}%
    \edef\curCenter{\lcurCenter}%
    \joinUnary%
}

\def\DisplayProof{%
    % Display (and purge) the proof tree.
    % Choose the appropriate vertical alignment.
    \ifnum \theLevel=1 \relax \else%x
        \errmessage{Proof tree badly specified.}%
    \fi%
    \edef\curBox{\thecur{myBox}}%
    \ifx\bottomAlignFlag\myTrue%
        \displace=0pt%
    \else%
        \displace=.5\ht\curBox%
        \ifx\centerAlignFlag\myTrue\relax
        \else%
                \advance\displace by -3pt%
        \fi%
    \fi%
    \leavevmode%
    \lower\displace\hbox{\copy\curBox}%
    \global\theLevel=0%
    \global\def\alwaysBuildScore{\defaultBuildScore}% Restore "always"
    \global\def\alwaysScoreFiller{\defaultScoreFiller}% Restore "always"
    \global\def\bottomAlignFlag{N}%
    \global\def\centerAlignFlag{N}%
    \resetRootPosition
    \resetInferenceDefaults%
    \ignorespaces
}

\def\buildSingleScore{% Make an hbox with a single score.
    \displace=\curScoreEnd%
    \advance \displace by -\curScoreStart%
    \global\setbox \myBoxD =%
        \hbox to \displace{\expandafter\xleaders\theScoreFiller\hfill}%
    %\global\setbox \myBoxD =%
        %\hbox{\hskip\curScoreStart\relax \box\myBoxD}%
}

\def\buildDoubleScore{% Make an hbox with a double score.
    \buildSingleScore%
    \global\setbox\myBoxD=%
        \hbox{\hbox to0pt{\copy\myBoxD\hss}\raise2pt\copy\myBoxD}%
}

\def\buildNoScore{% Make an hbox with no score (raise a little anyway)
    \global\setbox\myBoxD=\hbox{\vbox{\vskip1pt}}%
}

\def\doubleLine{%
    \gdef\buildScore{\buildDoubleScore}% Set next score to this type
    \ignorespaces
}
\def\alwaysDoubleLine{%
    \gdef\alwaysBuildScore{\buildDoubleScore}% Do double for rest of proof.
    \gdef\buildScore{\buildDoubleScore}% Set next score to be double
    \ignorespaces
}
\def\singleLine{%
    \gdef\buildScore{\buildSingleScore}% Set next score to be single
    \ignorespaces
}
\def\alwaysSingleLine{%
    \gdef\alwaysBuildScore{\buildSingleScore}% Do single for rest of proof.
    \gdef\buildScore{\buildSingleScore}% Set next score to be single
    \ignorespaces
}
\def\noLine{%
    \gdef\buildScore{\buildNoScore}% Set next score to this type
    \ignorespaces
}
\def\alwaysNoLine{%
    \gdef\alwaysBuildScore{\buildNoScore}%Do nolines for rest of proof.
    \gdef\buildScore{\buildNoScore}% Set next score to be blank
    \ignorespaces
}
\def\solidLine{%
    \gdef\theScoreFiller{\ruleScoreFiller}% Use solid horizontal line.
    \ignorespaces
}
\def\alwaysSolidLine{%
    \gdef\alwaysScoreFiller{\ruleScoreFiller}% Do solid for rest of proof
    \gdef\theScoreFiller{\ruleScoreFiller}% Use solid horizontal line.
    \ignorespaces
}
\def\dottedLine{%
    \gdef\theScoreFiller{\dottedScoreFiller}% Use dotted horizontal line.
    \ignorespaces
}
\def\alwaysDottedLine{%
    \gdef\alwaysScoreFiller{\dottedScoreFiller}% Do dotted for rest of proof
    \gdef\theScoreFiller{\dottedScoreFiller}% Use dotted horizontal line.
    \ignorespaces
}
\def\dashedLine{%
    \gdef\theScoreFiller{\dashedScoreFiller}% Use dashed horizontal line.
    \ignorespaces
}
\def\alwaysDashedLine{%
    \gdef\alwaysScoreFiller{\dashedScoreFiller}% Do dashed for rest of proof
    \gdef\theScoreFiller{\dashedScoreFiller}% Use dashed horizontal line.
    \ignorespaces
}
\def\kernHyps#1{%
    \gdef\hypKernAmt{#1}%
    \ignorespaces
}
\def\insertBetweenHyps#1{%
    \gdef\theHypSeparation{#1}%
    \ignorespaces
}

\def\centerAlignProof{%
    \def\centerAlignFlag{Y}%
    \def\bottomAlignFlag{N}%
    \ignorespaces
}
\def\bottomAlignProof{%
    \def\centerAlignFlag{N}%
    \def\bottomAlignFlag{Y}%
    \ignorespaces
}
\def\normalAlignProof{%
    \def\centerAlignFlag{N}%
    \def\bottomAlignFlag{N}%
    \ignorespaces
}

\def\LeftLabel#1{%
    \global\setbox\myBoxLL=\hbox{{#1}\hskip\labelSpacing}%
    \ignorespaces
}
\def\RightLabel#1{%
    \global\setbox\myBoxRL=\hbox{\hskip\labelSpacing #1}%
    \ignorespaces
}

\def\buildScoreLabels{%
    \scoreHeight = \ht\myBoxD%
    \scoreDepth = \dp\myBoxD%
    \leftLowerAmt=\ht\myBoxLL%
    \advance \leftLowerAmt by -\dp\myBoxLL%
    \advance \leftLowerAmt by -\scoreHeight%
    \advance \leftLowerAmt by \scoreDepth%
    \leftLowerAmt=.5\leftLowerAmt%
    \rightLowerAmt=\ht\myBoxRL%
    \advance \rightLowerAmt by -\dp\myBoxRL%
    \advance \rightLowerAmt by -\scoreHeight%
    \advance \rightLowerAmt by \scoreDepth%
    \rightLowerAmt=.5\rightLowerAmt%
    \displace = \curScoreStart%
    \advance\displace by -\wd\myBoxLL%
    \global\setbox\myBoxD =%
        \hbox{\hskip\displace%
            \lower\leftLowerAmt\copy\myBoxLL%
            \box\myBoxD%
            \lower\rightLowerAmt\copy\myBoxRL}%
    \global\thisAboveSkip = \ht\myBoxLL%
    \global\advance \thisAboveSkip by -\leftLowerAmt%
    \global\advance \thisAboveSkip by -\scoreHeight%
    \ifnum \thisAboveSkip<0 %
        \global\thisAboveSkip=0pt%
    \fi%
    \displace = \ht\myBoxRL%
    \advance \displace by -\rightLowerAmt%
    \advance \displace by -\scoreHeight%
    \ifnum \displace<0 %
        \displace=0pt%
    \fi%
    \ifnum \displace>\thisAboveSkip %
        \global\thisAboveSkip=\displace%
    \fi%
    \global\thisBelowSkip = \dp\myBoxLL%
    \global\advance\thisBelowSkip by \leftLowerAmt%
    \global\advance\thisBelowSkip by -\scoreDepth%
    \ifnum\thisBelowSkip<0 %
        \global\thisBelowSkip = 0pt%
    \fi%
    \displace = \dp\myBoxRL%
    \advance\displace by \rightLowerAmt%
    \advance\displace by -\scoreDepth%
    \ifnum\displace<0 %
        \displace = 0pt%
    \fi%
    \ifnum\displace>\thisBelowSkip%
        \global\thisBelowSkip = \displace%
    \fi%
    \global\thisAboveSkip = -\thisAboveSkip%
    \global\thisBelowSkip = -\thisBelowSkip%
    \global\advance\thisAboveSkip by\extraVskip% Extra space above line
    \global\advance\thisBelowSkip by\extraVskip% Extra space below line
}

\def\resetInferenceDefaults{%
    \global\def\theHypSeparation{\defaultHypSeparation}%
    \global\setbox\myBoxLL=\hbox{\defaultLeftLabel}%
    \global\setbox\myBoxRL=\hbox{\defaultRightLabel}%
    \global\def\buildScore{\alwaysBuildScore}%
    \global\def\theScoreFiller{\alwaysScoreFiller}%
    \gdef\hypKernAmt{0pt}% Restore to zero kerning.
}

\def\rootAtBottom{%
    \global\def\rootAtBottomFlag{Y}%
}

\def\rootAtTop{%
    \global\def\rootAtBottomFlag{N}%
}

\def\resetRootPosition{%
    \global\edef\rootAtBottomFlag{\defaultRootAtBottomFlag}
}

\def\alwaysRootAtBottom{%
    \global\def\defaultRootAtBottomFlag{Y}
    \rootAtBottom
}

\def\alwaysRootAtTop{%
    \global\def\defaultRootAtBottomFlag{N}
    \rootAtTop
}

${this.title}

Code Editor : bussproofs.sty