Revision 2baaae799ffe3be2c7ddafb788831372122243be authored by Joseph Wright on 01 February 2020, 08:09:36 UTC, committed by Joseph Wright on 01 February 2020, 08:09:36 UTC
1 parent fdcaec9
theorem.dtx
% \iffalse meta-comment
%
% Copyright (C) 1993-2020
%
% The LaTeX3 Project and any individual authors listed elsewhere
% in this file.
%
% This file is part of the Standard LaTeX `Tools Bundle'.
% -------------------------------------------------------
%
% It may be distributed and/or modified under the
% conditions of the LaTeX Project Public License, either version 1.3c
% of this license or (at your option) any later version.
% The latest version of this license is in
% https://www.latex-project.org/lppl.txt
% and version 1.3c or later is part of all distributions of LaTeX
% version 2005/12/01 or later.
%
% The list of all files belonging to the LaTeX `Tools Bundle' is
% given in the file `manifest.txt'.
%
% \fi
%
%%
%
%
\def\FMithmInfo{2014/10/28 v2.2c Theorem extension package (FMi)}
%
% \ProvidesFile{theorem.dtx}[\FMithmInfo]
%\iffalse % this is a METACOMMENT !
%%
%% Package `theorem' to use with LaTeX2e
%% Copyright (C) 1989-1995 Frank Mittelbach, all rights reserved.
%<+package>\@ifundefined{theorem@style}{}{\endinput}
%<+package>\NeedsTeXFormat{LaTeX2e}[1995/06/01]
%<+package>\ProvidesPackage{theorem}
%<+package> [\FMithmInfo]
%
% \fi
%
% \changes{v1.0}{87/05/07}{First draft.}
% \changes{v1.0a}{87/05/07}{`thistheoremstyle' added.}
% \changes{v1.1a}{87/07/29}{New concept: redefine the internal
% \protect\LaTeX{} commands `@xnthm' etc.}
% \changes{v1.1b}{87/07/31}{`theoremfont' used to specify font.}
% \changes{v1.2a}{88/01/08}{`@endtheorem' now globally defined.}
% \changes{v1.2b}{88/01/11}{`newtheorem' only allowed in the preamble.}
% \changes{v1.3a}{88/02/14}{`theoremfont' now a toks register.}
%
% \changes{v2.0a}{88/11/16}{New implementation and new documentation.}
% \changes{v2.0a}{88/11/16}{No layout changes but internal modifications
% old substyles won't work.}
% \changes{v2.0b}{89/01/30}{`global' used for all definitions.}
% \changes{v2.0c}{89/06/15}{Documentation translated to English.
% Thanks to LLL and Nina}
% \changes{v2.1a}{90/02/15}{Support for new font selection.}
% \changes{v2.2a}{94/02/03}{Cleanup for LaTeX2e}
%
% \DoNotIndex{\@endparenv,\@ifdefinable,\@ifnextchar,\@ifundefined}
% \DoNotIndex{\@namedef,\@nameuse,\@spaces,\@tempa,\@warning}
% \DoNotIndex{\ }
% \DoNotIndex{\begingroup,\bfseries}
% \DoNotIndex{\csname}
% \DoNotIndex{\def,\do,\docdate}
% \DoNotIndex{\endcsname,\endgroup,\endinput,\endtrivlist,\expandafter}
% \DoNotIndex{\filedate,\fileversion}
% \DoNotIndex{\gdef,\global}
% \DoNotIndex{\hbox,\hskip}
% \DoNotIndex{\ignorespaces,\input,\itshape,\item}
% \DoNotIndex{\labelsep,\let,\llap}
% \DoNotIndex{\makeatletter}
% \DoNotIndex{\noexpand}
% \DoNotIndex{\refstepcounter,\relax,\rlap}
% \DoNotIndex{\setlength,\slshape,\space,\string,\strut}
% \DoNotIndex{\the,\trivlist,\typeout}
% \DoNotIndex{\vbox}
% \DoNotIndex{\xdef}
%
% \def\deflabel#1{\ttfamily #1\hfill}
% \def\deflist#1{\begin{list}{}{\settowidth\labelwidth{\ttfamily #1}%
% \setlength\leftmargin\labelwidth
% \addtolength\leftmargin\labelsep
% \let\makelabel\deflabel}}
% \def\enddeflist{\end{list}}
% \def\envfont{\normalfont\ttfamily}
%
% \MakeShortVerb{\|}
%
% \newcommand{\TUB}{{\sl TUGboat\/}}
%
% \GetFileInfo{theorem.dtx}
% \title{An Extension of the
% \LaTeX{} theorem environment\thanks{This file
% has version number \fileversion, last
% revised \filedate.}}
% \author{Frank Mittelbach}
%
% \MaintainedByLaTeXTeam{tools}
% \maketitle
%
% \begin{abstract}
% The macros described in this paper yield an extension of the
% \LaTeX{} theorem mechanism. It is designed is to satisfy the
% different requirements of various journals. Thus, the
% layout of the ``theorems'' can be manipulated by determining a
% ``style''. This article describes not only the use, but
% also the definition, of the necessary macros.
% \end{abstract}
%
% \section*{Preface to version 2.2}
%
% For \LaTeXe{} this package did not need any fundamental changes. I
% only modified the messages generated so that theorem layout styles
% will show up with the |\listfiles| command and cleaned the section
% on the New Font Selection Scheme since this is now included in
% \LaTeX.
%
% \section*{Preface to version 2.1}
%
% This version is identical to 2.0g described in \TUB\ 10\#3 except
% for some internal defaults which are now set depending on the used
% font selection scheme.
%
% This was done to avoid unpleasant surprises if the new font selection
% scheme is in force. For further details see
% section~\ref{sec:newfonts} and \cite{bk:GMS94}.
%
% \section{Introduction}
%
% For our purposes here, ``theorems'' are labelled enunciations,
% often set off from the main text by extra space and a font change.
% Theorems, corollaries, conjectures, definitions, and remarks
% are all instances of ``theorems''. The ``header'' of these structures
% is composed of a label (such as \textsc{Theorem} or \textsc{Remark})
% and a number which serializes an item in the sequence of items
% with the same label.
%
% Shortly after the introduction of \LaTeX{} at the Fachbereich
% Mathematik in Mainz, the desire to manipulate the layout of
% ``theorems'' arose. In Mainz, the following two conventions came
% into general use:
% \begin{enumerate}
% \item The number of the theorem is shown in the margin.
% \item There is a line break at
% the end of the theorem header.
% \end{enumerate}
%
% Additionally, some journals require different formats which depend on
% the ``sort of theorem'': e.g.\ often remarks and definitions are set
% in |\upshape|, while |\itshape| is employed for main theorems.
%
% Confronted with these requirements, a theorem environment was
% developed in Mainz which allows separate determination of the
% layout of the ``theorems sets'', comparable to |\pagestyle|.
%
%
% \section{The user interface}
% \subsection{Defining new theorem sets}
%
% \DescribeMacro\newtheorem
% As in the original \LaTeX{} version, the command |\newtheorem|
% defines a new ``theorem set'' or ``theorem-like structure''.
% Two required arguments name the new environment and give the text
% to be typeset with each instance of the new ``set'', while
% an optional argument determines how
% the ``set'' is enumerated:
% \begin{description}
% \item[\ttfamily \bslash newtheorem\{foo\}\{bar\}]
% The theorem set {\envfont foo} (whose name is \texttt{bar})
% uses its own counter.
% \item[\ttfamily \bslash newtheorem\{foo2\}{[foo]}\{bar2\}]
% The theorem set {\envfont foo2} (printed name \texttt{bar2})
% uses the same counter as the theorem set \texttt{foo}.
% \item[\ttfamily \bslash newtheorem\{foo3\}\{bar3\}{[section]}]
% The theorem set {\envfont foo3} (printed name \texttt{bar3}) is
% enumerated within the counter \texttt{section}, i.e.\ with every
% new |\section| the enumeration begins again with 1, and
% the enumeration is composed from the section-number and the
% theorem counter itself.
% \end{description}
%
% \DescribeMacro\theoremstyle
% Additionally, the command |\theoremstyle| can define the layout
% of various, or all, theorem sets. It should be noted that any
% theorem set defined by |\newtheorem| is typeset in the
% |\theoremstyle| that is current at the time of the definition.
% Thus, the following
% \begin{verbatim}
% \theoremstyle{break} \newtheorem{Cor}{Corollary}
% \theoremstyle{plain} \newtheorem{Exa}{Example}[section]
%\end{verbatim} ^^A No blank at line start
% leads to the result that the set {\envfont Cor} is formatted in the
% style \texttt{break}, while the set {\envfont Exa} and all the
% following ones are formatted in the style \texttt{plain}, unless
% another |\theoremstyle| follows. Since the definitions installed by
% |\newtheorem| are global, one also can limit |\theoremstyle| locally
% by grouping braces.
%
% \DescribeMacro\theorembodyfont
% The choice of the font for the theorem body is completely
% independent of the chosen |\theoremstyle|; this has proven to
% be very advantageous. For example,
% \begin{verbatim}
% {\theorembodyfont{\upshape} \newtheorem{Rem}{Remark}}
%\end{verbatim}
% defines a theorem set {\envfont Rem}, which will be set in
% |\upshape| in the current layout (which in our example is
% \texttt{plain}). As with |\theoremstyle|, the |\theorembodyfont|
% chosen is that current at the time of |\newtheorem|. If
% |\theorembodyfont| is not specified or one defines
% |\theorembodyfont{}|, then the font used will be that defined by the
% |\theoremstyle|.
%
% \DescribeMacro\theoremheaderfont It is also possible to customize
% the font used for the theorem headers. This is, however, a global
% declaration, and therefore there should be at most one
% |\theoremheaderfont| declaration in the preamble.\footnote{If it is
% actually necessary to have different header fonts, one has to define
% new theorem styles (substituting the desired font) or specify the
% information directly in the \texttt{\bslash newtheorem} declaration
% (the unclean variant).}
%
% \DescribeMacro\theorempreskipamount
% \DescribeMacro\theorempostskipamount Two additional parameters
% affect the vertical space around the theorem environments:
% |\theorempreskipamount| and |\theorempostskipamount| define,
% respectively, the spacing before and after such an environment.
% These parameters apply for all theorem sets and can be manipulated
% with the ordinary length macros. They are rubber lengths,
% (`\textsf{skips}'), and therefore can contain \texttt{plus} and
% \texttt{minus} parts.
%
% Since the definition of theorem sets should---most sensibly---be
% placed in the preamble, we only allow installation there.
% It is therefore possible to release the memory used here after
% |\begin{document}|, in order to make room for other
% applications.
%
%
% \subsection{Existing theorem styles}
%
% The following theorem styles exist to date:
% \begin{deflist}{marginbreak}
% \item[plain]
% This theorem style emulates the original \LaTeX{} definition,
% except that additionally the parameters
% |\theorem...skipamount| are used.
% \item[break]
% In this style, the theorem header is followed by a line
% break.
% \item[marginbreak]
% The theorem number is set in the margin, and there is a line
% break as in \texttt{break}.
% \item[changebreak]
% Like \texttt{break}, but with header number and text
% interchanged.
% \item[change]
% Header number and text are interchanged, without a line break.
% \item[margin]
% The number is set in the left margin, without a line break.
% \end{deflist}
% All styles (except \texttt{plain}) select |\slshape| as the default
% |\theorembodyfont|.
%
%
% \subsection{Examples}
%
% Given the above theorem sets {\envfont Cor}, {\envfont Exa}
% and {\envfont Rem},
% suppose that the preamble also contains the declarations:
% \begin{verbatim}
% \theoremstyle{marginbreak} \newtheorem{Lem}[Cor]{Lemma}
% \theoremstyle{change}
% \theorembodyfont{\itshape} \newtheorem{Def}[Cor]{Definition}
%
% \theoremheaderfont{\scshape}
%\end{verbatim}
% Then the following are some typical examples of the typeset output
% resulting from their use.
%
% \begin{Cor}
% This is a sentence typeset in the theorem environment {\envfont
% Cor}.
% \end{Cor}
%
% \begin{Exa}
% This is a sentence typeset in the theorem environment {\envfont
% Exa}.
% \end{Exa}
%
% \begin{Rem}
% This is a sentence typeset in the theorem environment {\envfont
% Rem}.
% \end{Rem}
%
% \begin{Lem}[Ben User]
% This is a sentence typeset in the theorem environment {\envfont
% Lem}.
% \end{Lem}
%
% \begin{Def}[Very impressive Definition]
% This is a sentence typeset in the theorem environment {\envfont
% Def}.
% \end{Def}
%
% The last two examples show the effect of the optional argument to
% a theorem environment (it is the text typeset in parentheses).
%
%
% \section{Special Considerations}
% \label{sec:newfonts}
%
% Theoremheader and body are implemented as a unit. This means that
% the |\theoremheaderfont| will inherit characteristics of the
% |\theorembodyfont| in \LaTeXe. Thus, if for example
% |\theorembodyfont| is |\itshape| and |\theoremheaderfont|
% is |\bfseries| the font selected for the header will have the
% characteristics `bold extended italic'. If this is not desired one
% should set the |\theoremheaderfont| to something like
% \begin{verbatim}
% \theoremheaderfont{\normalfont\bfseries}
%\end{verbatim}
% i.e.\ supplying all necessary font information explicitly.
%
%
%
% \section{Acknowledgements}
%
% The publication of this set of macros was only possible with the
% help of Christina Busse (translating the manuscript into English),
% Joachim Pense (playing the r\^ole of typist), Chris Rowley
% (looking everything over) and many others providing useful
% suggestions.
%
% \StopEventually{%
% \begin{thebibliography}{9}
% \bibitem{bk:GMS94} \textsc{M.~Goossens}, \textsc{F.~Mittelbach}
% and \textsc{A.~Samarin}.
% \newblock The \LaTeX{} Companion.
% \newblock
% Addison-Wesley, Reading, Massachusetts, 1994.
% \bibitem{latex:source} \textsc{Lamport, Leslie.} \newblock
% \texttt{latex.tex}, version 2.09, date
% Feb. 1990.
% \end{thebibliography}
% \PrintIndex
% \PrintChanges}
%
%
% \section{The documentation driver file}
%
% The next bit of code contains the documentation driver file for
% \TeX{}, i.e., the file that will produce the documentation you are
% currently reading. It will be extracted from this file by the
% \texttt{docstrip} program. Since it is the first code in the file
% one can alternatively process this file directly with \LaTeXe{} to
% obtain the documentation.
%
% \begin{macrocode}
%<*driver>
\documentclass{ltxdoc}
\usepackage{theorem}
%<+driver>% The next few lines define theorem sets which are used
%<+driver>% in the example section of the documentation.
\theoremstyle{break} \newtheorem{Cor}{Corollary}
\theoremstyle{plain} \newtheorem{Exa}{Example}[section]
{\theorembodyfont{\upshape}\newtheorem{Rem}{Remark}}
\theoremstyle{marginbreak} \newtheorem{Lem}[Cor]{Lemma}
\theoremstyle{change}
\theorembodyfont{\itshape} \newtheorem{Def}[Cor]{Definition}
\theoremheaderfont{\scshape}
\RecordChanges
\begin{document}
\DocInput{theorem.dtx}
\end{document}
%</driver>
% \end{macrocode}
%
% \section{Definition of the Macros}
%
% If the file has been loaded before, we abort immediately. If not the
% package announces itself (this is actually done at the very top if
% the file---the way it is done isn't good style so don't copy it).
% \changes{v2.0e}{89/07/19}{Spaces removed from `typeout'.}
% \changes{v2.2b}{95/11/19}{Announce moved to top of file}
% \begin{macrocode}
%<*package>
%\@ifundefined{theorem@style}{}{\endinput}
%\def\FMithmInfo{1995/11/19 v2.2b Theorem extension package (FMi)}
%\ProvidesPackage{theorem}[\FMithmInfo]
% \end{macrocode}
%
%
% \subsection{Definition of theorem styles and fonts}
%
% All the definitions in this file are done globally to allow
% inputting this file inside a group.
%
% \begin{macro}{\theoremstyle}
% Before a theorem style can be installed, the chosen style must be
% known. For that reason, we must test to see that
% |\th@|\meta{style} is known or, more precisely, that it is
% different from |\relax|. If the style is not known then
% |\th@plain| is used.
% \begin{macrocode}
\gdef\theoremstyle#1{%
\@ifundefined{th@#1}{\@warning
{Unknown theoremstyle `#1'. Using `plain'}%
\theorem@style{plain}}%
% \end{macrocode}
% We save the theorem style to be used in the token register
% |\theorem@style|.
% \begin{macrocode}
{\theorem@style{#1}}%
% \end{macrocode}
% Now we ``evaluate'' the theorem style: this means, we call the
% macro |\th@|\meta{style} which will activate the relevant
% definitions which are contained in a separate file. This is done
% in a group to suppress changes to the current font. This could
% otherwise pose problems together with the new font selection
% scheme\footnote{When I printed the original article using the new
% font selection scheme I ended with a document with slanted
% typefaces (text headings and all) simply because one of the
% theorem styles used \texttt{\bslash sl} at toplevel.} if the
% |\th@|\meta{style} is evaluated a second time.
% \changes{v2.1a}{90/02/15}{Group added around `th@..}
% \changes{v2.1a}{90/02/15}{Reseting of `..@begintheorem removed.}
% \begin{macrocode}
\begingroup
\csname th@\the\theorem@style \endcsname
\endgroup}
% \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\@begintheorem}
% \changes{v2.1a}{90/02/15}{Relaxed at toplevel.}
% \begin{macro}{\@opargbegintheorem}
% \changes{v2.1a}{90/02/15}{Relaxed at toplevel.}
% We reset |\@begintheorem| and |\@opargbegintheorem| to
% |\relax| since these commands are no longer necessary at
% toplevel. This will save a few tokens.
% \begin{macrocode}
\global\let\@begintheorem\relax
\global\let\@opargbegintheorem\relax
% \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\theorem@style}
% Obviously the \textsf{token} register used above has to be
% allocated. To assure the utmost compatibility with the
% original \LaTeX{} definition, we set the default theorem style to
% \texttt{plain}, which implements the usual \LaTeX{} convention.
% \changes{v2.0f}{89/07/20}{Unnecessary `global' removed.}
% \begin{macrocode}
\newtoks\theorem@style
\global\theorem@style{plain}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\theorembodyfont}
% \begin{macro}{\theorem@bodyfont}
% If the |\theorembodyfont| is set by the user then it should not
% interact with the default font set in the theorem style. When the
% new font selection is in force this may happen if, for example,
% the default is |\itshape| and the new |\theorembodyfont| is
% |\sffamily|. So we add a |\reset@font| command in front of the
% user definition.
% \changes{v2.0f}{89/07/20}{Unnecessary `global' removed.}
% \changes{v2.0g}{89/09/19}{`theoremfont to `theorembodyfont.}
% \changes{v2.1c}{92/06/22}{`reset@font added and logic changed.}
% \changes{v2.1d}{92/10/28}{Reset to empty if arg is empty}
% \begin{macrocode}
\gdef\theorembodyfont#1{%
% \end{macrocode}
% We check if the argument supplied is empty and if so put nothing
% into the |\theorem@bodyfont| token register to allow for
% |\theorembodyfont{}| as a mean of using the default of the
% current |\theoremstyle|.
% \begin{macrocode}
\def\@tempa{#1}%
\ifx\@tempa\@empty
\theorem@bodyfont{}%
\else
\theorem@bodyfont{\reset@font#1}%
\fi
}
\newtoks\theorem@bodyfont
\global\theorem@bodyfont{}
% \end{macrocode}
% \end{macro}
% \end{macro}
%
%
% \begin{macro}{\theoremheaderfont}
% \changes{v2.0g}{89/09/19}{Macro added.}
% The font for the theorem headers is handled differently because
% this definition applies to all theorem styles.
% \begin{macrocode}
\gdef\theoremheaderfont#1{\gdef\theorem@headerfont{#1}%
% \end{macrocode}
% After using the macro once it is redefined to produce an error
% message.
% \begin{macrocode}
\gdef\theoremheaderfont##1{%
\typeout{\string\theoremheaderfont\space should be used
only once.}}}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\theorem@headerfont}
% \changes{v2.0g}{89/09/19}{Macro added.}
% To set the |\theorem@headerfont| default we first test if
% the new fontselection scheme is in force.
% \changes{v2.1a}{90/02/15}{Support for new font selection.}
% \begin{macrocode}
\ifx\upshape\undefined
% \end{macrocode}
% If not we define it to expand into |\bfseries|. We don't use
% |\let| just in case a following style option redefines this
% macro.
% \begin{macrocode}
\gdef\theorem@headerfont{\bfseries}
% \end{macrocode}
% Otherwise we reset the current shape before calling |\bfseries|.
% \begin{macrocode}
\else \gdef\theorem@headerfont{\normalfont\bfseries}\fi
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\th@plain}
% \begin{macro}{\th@break}
% \begin{macro}{\th@marginbreak}
% \begin{macro}{\th@changebreak}
% \begin{macro}{\th@change}
% \begin{macro}{\th@margin}
% The different styles are defined in macros such as
% |\th@plain|. Since memory space is precious in
% ``non-Big-versions'', we have to avoid offering too many unused
% definitions. Therefore we define these styles in separate files
% that can be loaded on demand. Thus the commands themselves only
% load these files. We use |\@input@| a \LaTeXe{} internal command
% that ensures that the file will be listed with |\listfiles|
% \changes{v2.2a}{94/02/02}{Use `@input@ to load theorem layout files}
% \begin{macrocode}
\gdef\th@plain{\@input@{thp.sty}}
\gdef\th@break{\@input@{thb.sty}}
\gdef\th@marginbreak{\@input@{thmb.sty}}
\gdef\th@changebreak{\@input@{thcb.sty}}
\gdef\th@change{\@input@{thc.sty}}
\gdef\th@margin{\@input@{thm.sty}}
% \end{macrocode}
% This list will be expanded when new styles become
% available. For testing, just append new theorem substyles
% as document options.
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
%
%
%
% \subsection{Definition of a new theorem set}
%
% As already pointed out, a new theorem environment can be defined in
% three different ways:
% \begin{verbatim}
% \newtheorem{Lem}{Lemma}
% \newtheorem{Lem}{Lemma}[section]
% \newtheorem{Lem}[Theorem]{Lemma}
%\end{verbatim}
% The function of the macro |\newtheorem| is to recognize these cases
% and then to branch into one of the three macros |\@ynthm|, |\@xnthm|
% or |\@othm|. This mechanism is adopted unchanged from
% \cite{latex:source}; the essential point here is that, for example,
% in the second case, the arguments \texttt{Lem}, \texttt{Lemma} and
% \texttt{section} are passed over to the macro |\@xnthm|.
%
% We inspect this case first because the others present fewer problems,
% and thus are easily derived from this one.
%
% \begin{macro}{\@xnthm}
% For our example arguments, the macro |\@xnthm| must fulfill
% the following:
% \begin{itemize}
% \item
% Define a new \LaTeX-counter `Lem'
% \item
% reset this counter within a |\section|
% \item
% define the macro |\theLem|
% \item
% define the environment macros |\Lem| and
% |\endLem| using the current
% |\theoremstyle| and |\theorem@bodyfont|.
% \end{itemize}
% Obviously, all this should happen only if the first argument
% of |\@xnthm| (i.e.\ \texttt{Lem} in our example) is chosen so
% as not to conflict with any previously defined commands or
% environments. This test is performed by the \LaTeX{} macro
% |\@ifdefinable|.
% \begin{macrocode}
\gdef\@xnthm#1#2[#3]{\expandafter\@ifdefinable\csname #1\endcsname
% \end{macrocode}
% Therefore, the first argument of |\@ifdefinable| is the
% expansion (in the example, |\Lem|) of
% |\csname||#1\endcsname|. The second argument is
% executed only if the test has been completed successfully.
% \begin{macrocode}
{%
% \end{macrocode}
% Now we define the new counter. The names of the \LaTeX{}
% macros employed should speak for themselves:
% \changes{v2.2b}{1995/10/07}{Use \cs{@newctr}}
% \changes{v2.2c}{1995/11/23}{Use \cs{@newctr} properly.}
% \begin{macrocode}
\@definecounter{#1}\@newctr{#1}[#3]%
% \end{macrocode}
% Using |\@newctr| will give a proper error message if the counter
% in |#3| is not defined.
% In defining `|\theLem|' we must generate the desired macro
% name by use of |\expandafter| and |\csname|.
% \begin{macrocode}
\expandafter\xdef\csname the#1\endcsname
% \end{macrocode}
% An |\xdef| is used in order to make the definition global,
% and to ensure that it contains the replacement texts of
% |\@thmcountersep| and |\@thmcounter|.\footnote{These
% two macros can be defined by the document style. Their default
% values produce a `\texttt{.}' as separation and an arabic
% representation of the number.} However, not everything should be
% expanded. For example, it saves space to use |\thesection|
% instead of its---at times---lengthy expansion.
% \begin{macrocode}
{\expandafter \noexpand \csname the#3\endcsname
\@thmcountersep \@thmcounter{#1}}%
% \end{macrocode}
% Thus with the defaults of \LaTeX{}, |\theLem| would be
% replaced by the command sequence |\thesection.\arabic{Lem}|.
%
% We will now look at the definition of the macro which is executed
% at the beginning of the actual environment (in our example this
% macro is |\Lem|). It should be noted that we use an
% ``|\expandafter| trick'' to expand only certain parts of the
% replacement text at the time of the definition.
% \begin{macrocode}
\def\@tempa{\global\@namedef{#1}}%
\expandafter \@tempa \expandafter{%
% \end{macrocode}
% First, the macro that contains the current definitions of
% |\@begintheorem| and |\@opargtheorem| should be called
% up. The name of this macro---as is already known---has the form
% |\th@|\meta{theorem\ style}; therefore, it must be called by
% \begin{macrocode}
\csname th@\the \theorem@style
% \end{macrocode}
% In addition the default theorem font should be changeable, i.e.\
% we have to insert the contents of |\theorem@bodyfont|. For
% that reason, we expand even further, beyond |\endcsname|,
% and thus insert the contents of the \textsf{token} register
% |\theorem@bodyfont| in the replacement text.
% \begin{macrocode}
\expandafter \endcsname \the \theorem@bodyfont
% \end{macrocode}
% Now it is time to call the macro |\@thm| which takes over
% the further processing. It has two arguments: the current
% counter name (in our example, \texttt{Lem}), and the text of the
% label (in our example, \texttt{Lemma}).
% \begin{macrocode}
\@thm{#1}{#2}}%
% \end{macrocode}
% With this, the `sub-definition' is complete. The macro
% |\@endtheorem| ends a theorem environment and is, so far, nothing
% but an |\endtrivlist|. (Hence it is defined globally, and not
% within the theorem styles.\footnote{This has to be changed as
% soon as theorem styles that change \texttt{\bslash @endtheorem}
% exist. In such a case, all existing styles must be changed as
% well since they will have to reset the macro.}) Therefore, we can
% set it equivalent to the macro that ends the theorem set (in our
% example, |\endLem|). However, if some day theorem styles exist
% that do change |\@endtheorem|, we would have to use the
% commented-out line instead.
% \begin{macrocode}
\global \expandafter \let \csname end#1\endcsname \@endtheorem
% \global\@namedef{end#1}{\@endtheorem}%
% \end{macrocode}
% With these commands all the required definitions are employed,
% unless the test |\@ifdefinable| has failed. Therefore, we
% end the second argument of this macro and with it the definition
% of |\@xnthm|.
% \begin{macrocode}
}}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@ynthm}
% The definition of |\@ynthm| is completely analogous. In
% this case the new counter that is defined is not reset within
% another counter; thus the definition of |\the...|
% is simplified:
% \begin{macrocode}
\gdef\@ynthm#1#2{\expandafter\@ifdefinable\csname #1\endcsname
{\@definecounter{#1}%
\expandafter\xdef\csname the#1\endcsname{\@thmcounter{#1}}%
% \end{macrocode}
% The rest of the definition corresponds literally to that of
% |\@xnthm|:
% \begin{macrocode}
\def\@tempa{\global\@namedef{#1}}\expandafter \@tempa
\expandafter{\csname th@\the \theorem@style \expandafter
\endcsname \the\theorem@bodyfont \@thm{#1}{#2}}%
\global \expandafter \let \csname end#1\endcsname \@endtheorem}}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@othm}
% The definition of |\@othm| does not contain anything new.
% \begin{macrocode}
\gdef\@othm#1[#2]#3{%
% \end{macrocode}
% \changes{v2.2b}{95/10/07}{Build in check for counter defined}
% We do not define a new counter but instead use one that has
% already been defined. Thus the only definition we need is that
% of this pseudo-counter (i.e.\ |\the|\meta{env.\ name}).
% First we check if |#2| corresponds to a known counter name.
% \begin{macrocode}
\expandafter\ifx\csname c@#2\endcsname\relax
\@nocounterr{#2}%
\else
\expandafter\@ifdefinable\csname #1\endcsname
{\expandafter \xdef \csname the#1\endcsname
{\expandafter \noexpand \csname the#2\endcsname}%
% \end{macrocode}
% All other parts of the definition can be adopted from
% |\@xnthm|. We have to remember, though, that in this case
% the name of the current counter and the theorem label have moved
% to the second and third arguments.
% \begin{macrocode}
\def\@tempa{\global\@namedef{#1}}\expandafter \@tempa
\expandafter{\csname th@\the \theorem@style \expandafter
\endcsname \the\theorem@bodyfont \@thm{#2}{#3}}%
\global \expandafter \let \csname end#1\endcsname \@endtheorem}%
\fi}
% \end{macrocode}
% \end{macro}
%
% \subsection{Macros that are employed in a {\envfont theorem}
% environment}
%
% \begin{macro}{\@thm}
% The macro |\@thm| has to increase the current counter. Then,
% depending on whether the environment has (or does not have) an
% optional argument, it has to branch into either |\@begintheorem|
% or |\@opargtheorem|.
% \begin{macrocode}
\gdef\@thm#1#2{\refstepcounter{#1}%
% \end{macrocode}
% Now we start a {\envfont trivlist} environment, and give
% |\@topsep| and |\@topsepadd| the values of the \textsf{skip}
% registers |\theorempreskipamount| and |\theorempostskipamount|.
% The value in |\@topsep| is the vertical space that is inserted by
% the first (and only) |\item| in our |\trivlist| whilst
% |\@topsepadd| is inserted by |\@endparenv| at the end of that
% {\envfont trivlist} environment. By using these registers, we
% obtain the desired space around a {\envfont theorem} environment.
% \begin{macrocode}
\trivlist
\@topsep \theorempreskipamount % used by first \item
\@topsepadd \theorempostskipamount % used by \@endparenv
% \end{macrocode}
% Now we have to test whether an optional argument has been given.
% \changes{v2.0d}{89/07/18}{Forgotten percent added.}
% \begin{macrocode}
\@ifnextchar [%
% \end{macrocode}
% If there is an optional argument, we will call |\@ythm|, and
% move the arguments read back into the input stream.
% \begin{macrocode}
{\@ythm{#1}{#2}}%
% \end{macrocode}
% If not, we call |\@begintheorem|. Its first argument is the
% name of the theorem set (hence the second argument of
% |\@thm|). Its second argument is the macro that produces the
% current number.
% \begin{macrocode}
{\@begintheorem{#2}{\csname the#1\endcsname}\ignorespaces}}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@xthm}
% \begin{macro}{\@ythm}
% Both these macros were originally called by |\@thm|. We do
% not need |\@xthm| anymore, hence we reset it to
% |\relax|. The definition of |\@ythm| has not changed at
% all from its definition in \LaTeX. In order to make the macros
% easier to understand, we will
% nevertheless present it (commented out).
% \begin{macrocode}
\global\let\@xthm\relax
% \def\@ythm#1#2[#3]{\@opargbegintheorem{#2}{\csname
% the#1\endcsname}{#3}\ignorespaces}
%</package>
% \end{macrocode}
% The primitive |\ignorespaces| in |\@ythm| and
% |\@thm| is needed to remove the spaces between the
% |\begin{...}| and the actual text.
% \end{macro}
% \end{macro}
%
%
% \subsection{Definition of the theorem substyles}
%
% As already pointed out, the theorem substyles, defined below, are
% only loaded when necessary. Note that all these substyles, except
% \texttt{plain}, have |\slshape| as the default body font.
%
% \subsubsection{The \texttt{plain} style}
%
% \label{dok:th@plain} As the following macros use |@|, we have
% to locally set the |\catcode| of this symbol to ``letter''.
% This happens within a group, so that we do not have to worry about
% which |\catcode| that symbol had before.
% \begin{macrocode}
%<*thp>
\begingroup \makeatletter
% \end{macrocode}
% Since we are now within a group, we must make all definitions
% globally. First we make sure that \texttt{theorem.sty} is loaded.
% This will allow us to use this file as a document style option
% without having to call \texttt{theorem} itself as an option. At the
% same time, we assure that at least version 2 is loaded, since
% |\theorem@style| was not defined in earlier versions.
% \begin{macrocode}
\@ifundefined{theorem@style}{\input{theorem.sty}}{}
\ProvidesFile{thp.sty}
[\FMithmInfo]
% \end{macrocode}
%
%
% \begin{macro}{\th@plain}
% \begin{macro}{\@begintheorem}
% \begin{macro}{\@opargbegintheorem}
% |\theoremstyle{plain}| corresponds to the original
% definition, except that the distances to the surrounding text are
% determined by the parameters |\theorempreskipamount| and
% |\theorempostskipamount|.
% First we set the default body font.
% \begin{macrocode}
\gdef\th@plain{\normalfont\itshape
% \end{macrocode}
% Then we define |\@begintheorem| and
% |\@opargbegintheorem|. These two macros define how the
% header of a theorem is typeset. |\@opargbegintheorem| will
% be called if a \textsf{theorem} environment with an optional
% argument is encountered; otherwise, the header is constructed by
% calling |\@begintheorem|. If one of these macros is
% executed, we are within a \textsf{trivlist} environment started by
% |\@thm|. So the theorem header is produced with an
% |\item| command.
%
% Instead of specifying the header font directly, all standard
% theorem styles use the |\theorem@headerfont| macro to allow
% customization. The extra space (|\labelsep|) is necessary
% because of problems in the \textsf{trivlist} environment.
% \begin{macrocode}
\def\@begintheorem##1##2{%
\item[\hskip\labelsep \theorem@headerfont ##1\ ##2]}%
% \end{macrocode}
% The definition of |\@opargbegintheorem| is completely
% analogous. The only difference is the fact that there exists a
% third argument (which is the optional parameter of the
% environment and contains additional information about the
% theorem). Customarily we enclose it in parentheses.
% \begin{macrocode}
\def\@opargbegintheorem##1##2##3{%
\item[\hskip\labelsep \theorem@headerfont ##1\ ##2\ (##3)]}}
% \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \noindent
% We conclude with an |\endgroup| to restore the
% |\catcode| of |@|.
% \begin{macrocode}
\endgroup
%</thp>
% \end{macrocode}
%
%
% \subsubsection{The \texttt{break} style}
%
% This style option is stored in the file |thb.sty|.
% For the next two lines see the documentation for |\th@plain| on
% page~\pageref{dok:th@plain}.
% \begin{macrocode}
%<*thb>
\begingroup \makeatletter
\@ifundefined{theorem@style}{\input{theorem.sty}}{}
\ProvidesFile{thb.sty}
[\FMithmInfo]
% \end{macrocode}
%
% \begin{macro}{\th@break}
% |\theoremstyle{break}| produces a line break after the name
% of the theorem. The font is |\slshape|. Hence, we define
% |\th@break| as follows:
% \begin{macrocode}
\gdef\th@break{\normalfont\slshape
\def\@begintheorem##1##2{\item[%
% \end{macrocode}
% We run into the following problem: it is not possible to create
% the header with |\item[|\meta{title}|]| and then start
% a new line by, for example, |\mbox{}\\|. Such a definition
% will fail whenever a list environment follows immediately. With
% the above construction, the |\mbox{}| causes the switch
% |@inlabel| (cf.\ definition of |\list| and
% |\trivlist| in \cite{latex:source}) to be set to \texttt{false}
% and so the following list will insert additional vertical
% space (|\topskip|). This is quite annoying. Therefore, we
% create the line break within the |\item|. In order to ensure
% that the text will begin at the proper position in the following
% line, we simply pretend that the label does not take any
% room.\footnote{This will lead to problems whenever very high
% symbols occurring in the line tower into the
% heading. So, something else has to be done here sometime.}
% \begin{macrocode}
\rlap{\vbox{\hbox{\hskip \labelsep\theorem@headerfont ##1\ ##2}%
\hbox{\strut}}}]}%
% \end{macrocode}
% Again, the definition of |\@opargbegintheorem| is
% completely analogous.
% \begin{macrocode}
\def\@opargbegintheorem##1##2##3{%
\item[\rlap{\vbox{\hbox{\hskip \labelsep \theorem@headerfont
##1\ ##2\ (##3)}%
\hbox{\strut}}}]}}
\endgroup
%</thb>
% \end{macrocode}
% \end{macro}
%
%
% \subsubsection{The \texttt{changebreak} style}
%
% \begin{macrocode}
% This style option is stored in the file |thcb.sty|.
% \begin{macrocode}
%<*thcb>
\begingroup \makeatletter
\@ifundefined{theorem@style}{\input{theorem.sty}}{}
\ProvidesFile{thcb.sty}
[\FMithmInfo]
% \end{macrocode}
%
% \begin{macro}{\th@changebreak}
% The \texttt{change-break} theorem style is like \texttt{break}
% but with interchange of theorem name and theorem number. Thus we
% define |\th@changebreak| as follows:
% \begin{macrocode}
\gdef\th@changebreak{\normalfont\slshape
\def\@begintheorem##1##2{\item
[\rlap{\vbox{\hbox{\hskip\labelsep \theorem@headerfont ##2\ ##1}%
\hbox{\strut}}}]}%
\def\@opargbegintheorem##1##2##3{%
\item[\rlap{\vbox{\hbox{\hskip\labelsep \theorem@headerfont
##2\ ##1\ (##3)}%
\hbox{\strut}}}]}}
\endgroup
%</thcb>
% \end{macrocode}
% \end{macro}
%
%
% \subsubsection{The \texttt{change} style}
%
% This style option is stored in the file |thc.sty|.
% \begin{macrocode}
%<*thc>
\begingroup \makeatletter
\@ifundefined{theorem@style}{\input{theorem.sty}}{}
\ProvidesFile{thc.sty}
[\FMithmInfo]
% \end{macrocode}
%
% \begin{macro}{\th@change}
% The \texttt{change} theorem style corresponds to the
% \texttt{change break} style without a linebreak after the header.
% To say it in another way, it's the same as the \texttt{plain}
% style but with number and name interchanged and |\slshape| as the
% default font.
% \begin{macrocode}
\gdef\th@change{\normalfont\slshape
\def\@begintheorem##1##2{\item
[\hskip\labelsep \theorem@headerfont ##2\ ##1]}%
\def\@opargbegintheorem##1##2##3{%
\item[\hskip\labelsep \theorem@headerfont ##2\ ##1\ (##3)]}}
\endgroup
%</thc>
% \end{macrocode}
% \end{macro}
%
%
% \subsubsection{The \texttt{marginbreak} style}
%
% This style option is the one used most often at Mainz. It is saved
% in the file |thmb.sty|.
% \begin{macrocode}
%<*thmb>
\begingroup \makeatletter
\@ifundefined{theorem@style}{\input{theorem.sty}}{}
\ProvidesFile{thmb.sty}
[\FMithmInfo]
% \end{macrocode}
%
% \begin{macro}{\th@marginbreak}
% The \texttt{margin break} style is nearly the same as the
% \texttt{change break} style. The only difference is the placement
% of the theorem number. We use |\llap| to place it in the left
% margin.
%
% In this style |\labelsep| denotes the separation between the
% number and the text.
% \begin{macrocode}
\gdef\th@marginbreak{\normalfont\slshape
\def\@begintheorem##1##2{\item
[\rlap{\vbox{\theorem@headerfont
\hbox{\llap{##2}\hskip\labelsep ##1}%
\hbox{\strut}}}]}%
\def\@opargbegintheorem##1##2##3{%
\item[\rlap{\vbox{\theorem@headerfont
\hbox{\llap{##2}\hskip\labelsep ##1\ (##3)}%
\hbox{\strut}}}]}}
\endgroup
%</thmb>
% \end{macrocode}
% \changes{v2.1c}{90/02/17}{`endgroup outside macrocode env.}
% \end{macro}
%
%
%
% \subsubsection{The \texttt{margin} style}
%
% This style option is stored in the file |thm.sty|.
% \begin{macrocode}
%<*thm>
\begingroup \makeatletter
\@ifundefined{theorem@style}{\input{theorem.sty}}{}
\ProvidesFile{thm.sty}
[\FMithmInfo]
% \end{macrocode}
%
% \begin{macro}{\th@margin}
% Again this is only a variant of the theorem styles described
% above without any new ideas.
% \begin{macrocode}
\gdef\th@margin{\normalfont\slshape
\def\@begintheorem##1##2{\item
[\theorem@headerfont \llap{##2}\hskip\labelsep ##1]}%
\def\@opargbegintheorem##1##2##3{%
\item[\theorem@headerfont \llap{##2}\hskip\labelsep ##1\ (##3)]}}
\endgroup
%</thm>
% \end{macrocode}
% \end{macro}
%
%
%
%
% \subsection{Final Definitions}
%
% \begin{macro}{\theorempreskipamount}
% \begin{macro}{\theorempostskipamount}
% The \textsf{skip} parameters that regulate the vertical empty space
% before and after the {\envfont theorem} environment have
% to be allocated as well.
% \changes{v2.0f}{89/07/20}{Unnecessary `global' removed.}
% \begin{macrocode}
%<*package>
\newskip\theorempreskipamount
\newskip\theorempostskipamount
% \end{macrocode}
% Since we have used the same values for all theorem sets, we now can
% assign them.
% \begin{macrocode}
\global\setlength\theorempreskipamount{12pt plus 5pt minus 3pt}
\global\setlength\theorempostskipamount{8pt plus 3pt minus 1.5pt}
% \end{macrocode}
% \end{macro}
% \end{macro}
%
%
% \begin{macro}{\@endtheorem}
% The same holds for the macro |\@endtheorem|, which ends a
% {\envfont theorem} environment. Since it is the same for all
% theorem sets, it is removed from the macros |\th@|\meta{style}.
% It simply ends the {\envfont trivlist} environment, which was
% begun in |\@thm|.
% \begin{macrocode}
\global\let\@endtheorem=\endtrivlist
% \end{macrocode}
% \end{macro}
%
%
%
% \begin{macro}{\@preamblecmds}
% All macros defined above are to be used only in the preamble.
% Therefore, we insert them in |\@preamblecmds| which will disable
% them at begin document. This is done by the internal \LaTeXe{}
% command |\@onlypreamble|.
% \changes{v2.0g}{89/09/19}{`theoremheaderfont and `theorembodyfont
% added.}
% \changes{v2.2a}{94/02/03}{Use \LaTeXe{} interface}
% \begin{macrocode}
\@onlypreamble\@xnthm
\@onlypreamble\@ynthm
\@onlypreamble\@othm
\@onlypreamble\newtheorem
\@onlypreamble\theoremstyle
\@onlypreamble\theorembodyfont
\@onlypreamble\theoremheaderfont
% \end{macrocode}
% \end{macro}
%
% Finally we declare the \texttt{plain} theorem style to be the default.
% \changes{v2.1b}{90/06/04}{Fixed missing `item by declaring default
% style.}
% \begin{macrocode}
\theoremstyle{plain}
%</package>
% \end{macrocode}
%
% \Finale
\endinput
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