% \iffalse meta comment
% File: booktabs.dtx Copyright (C) 1995 Simon Fear
% \fi
%
% \iffalse
%<package>\NeedsTeXFormat{LaTeX2e}
%<package>\ProvidesPackage{booktabs}
%<package>         [1995/11/06 v1.00 publication quality tables]
%
%<*driver>
\documentclass{ltxdoc}
\usepackage{booktabs}
  \title{Publication quality tables in \LaTeX
        \thanks{This file
        has version number v1.00, last
        revised 6 November 1995.}}
 \author{Simon Fear\\University of Liverpool}
 \date{Printed \today}
 \MakeShortVerb{\=}
 \MakeShortVerb{\"}
\begin{document}
 \maketitle
 \DeleteShortVerb{\|}
 \DocInput{booktabs.dtx}
\end{document}
%</driver>
% \fi
%
% \CheckSum{319}
%
% \begin{abstract}
% This article describes some additional commands to enhance
% the quality of tables in \LaTeX. Guidelines are given as
% to what constitutes a good table in this context.
% \end{abstract}
%
% \section{Introduction}
%
% The routines described below are to enable the easy production
% of tables such as (should) appear in published scientific books and
% journals. What distinguishes these from the tables plain
% \LaTeX{} is able to produce is additional space above and below rules
% and rules of varying `thickness'. What further distinguishes them from
% the tables many people {\em do} produce using \LaTeX{} is the
% absence of vertical rules and double rules.
%
% I must draw a clear
% distinction between what I mean by a {\em formal table},
% which is a set of values/labels in columns, as distinct from
% what I will call a {\em tableau}, which is the kind of thing
% illustrated in the \LaTeX{} manual, and which is increasingly
% common as the output of of
% many database/management systems, that is with
% icons in abundance, and probably colour
% into the bargain. The layout of a {\em tableau} is determined
% (hopefully) as a one-off, given a jumble of material the
% designer is trying to combine into a meaningful configuration.
% But the layout of a {\em table} has been established over
% literally centuries of experience and should only be altered in
% truly extraordinary circumstances.
%
% By way of illustration, consider this tableau from the \LaTeX{}
% manual (p. 64 old edition):
%
% \begin{center}
% \begin{tabular}{||l|lr||} \hline
% gnats     & gram      & \$13.65 \\ \cline{2-3}
%           & each      & .01 \\ \hline
% gnu       & stuffed   & 92.50 \\ \cline{1-1} \cline{3-3}
% emu       &           & 33.33 \\ \hline
% armadillo & frozen    & 8.99 \\ \hline
% \end{tabular}
% \end{center}
%
% This is a hotch-potch of information that is probably
% reasonably clearly presented as is (but is the emu stuffed or
% not?). However, as a published table, this should 
% certainly instead appear along the lines suggested
% further down the page in the manual:
%
% \begin{center}
% \begin{tabular}{@{}llr@{}} \toprule
% \multicolumn{2}{c}{Item} \\ \cmidrule(r){1-2}
% Animal & Description & Price (\$)\\ \midrule
% Gnat  & per gram  & 13.65 \\
%       & each      & 0.01 \\
% Gnu   & stuffed   & 92.50 \\
% Emu   & stuffed   & 33.33 \\
% Armadillo & frozen & 8.99 \\ \bottomrule
% \end{tabular}
% \end{center}
%
% It may be noted that it in fact takes much less work to lay
% this out as a formal table; we don't have to work out a new
% layout for everything we do. Moreover, we can be almost certain
% that the data cannot be misread (because the reader does not
% have to learn how to read each of the infinite number of
% different possible tableaux).
%
% The above table cannot be produced in pure \LaTeX,
% unfortunately. It can be laid out as it should be, but despite
% your best efforts, using plain =\hline= commands produces
%
% \begin{center}
% \begin{tabular}{@{}llr@{}} \hline
% \multicolumn{2}{c}{Item} \\ \cline{1-2}
% Animal & Description & Price (\$)\\ \hline
% Gnat  & per gram  & 13.65 \\
%       & each      & 0.01 \\
% Gnu   & stuffed   & 92.50 \\
% Emu   & stuffed   & 33.33 \\
% Armadillo & frozen & 8.99 \\ \hline
% \end{tabular}
% \end{center}
%
% Note (if it is not already obvious) that there is not enough
% space between the top line and the capital I of `Item', and so
% on for all the lines: contrast with the previous version. Also,
% the top and bottom rules (ie lines) in the first version are
% heavier than the middle rule, which is turn heavier than the
% subrule underneath `Item'. Yes, I {\em know} you can redefine
% =\doublerulesep= and then use =\hline\hline= to get something
% near the same effect, and you can use struts to improve
% the spacing. But that is a fiddle and you should not have to
% think of such things. The =booktabs= style defines its commands so
% that such things are taken care of automatically.
%
% In general, I would say that 
% this package is of no interest to those looking for
% an alternative to Pic\TeX{} to conjure up fancy tableaux.
% Rather, it is a style guide for authors of scientific papers
% and books as regards table layout. It is not going too far to
% say that if you cannot
% create a table using the commands in this package, you have
% designed it wrong.
%
% \subsection{A note on terminology}
%
% In British typesetting, a `line' is always called a `rule'. Perhaps
% confusingly (for historic reasons in fact), the `thickness' of
% rule is often referred to as is its `width' (whereas just about
% everyone else would call this `depth' or `height', if they were thinking
% of a horizontal rule). A `thick black line' is called a `heavy
% rule'. I have used this terminology in most of the new commands
% below. If nothing else it avoid confusion with =\hline=.
%
% \section{The layout of formal tables}
%
% You will not go far wrong if you remember two simple 
% commandments at all times:
% \begin{enumerate} 
%   \item Never, ever use vertical rules.
%   \item Never use double rules.
% \end{enumerate}
% These commandments may seem extreme but in years of experience I have
% never found a good argument in favour of breaking them. For
% example, if you feel that the information in the left half of 
% a table is so different from that on the right that it needs
% to be separated by a vertical line, then you should use two
% tables instead. The second commandment is very, very occasionally
% violated: I have worked for a publisher who insisted on a
% double light rule above a row of totals. But this would not
% have been my choice.
%
% There are three further guidelines I might mention here as they
% are so poorly known outside the circles of professional
% typesetters and subeditors:
% \begin{enumerate}
%   \item Put the units in the column heading (not in the body of
%           the table).
%   \item Always precede a decimal point by a digit; thus 0.1
%       {\em not} just .1.
%   \item Do not use `ditto' signs or any other such convention to
%       repeat a previous value. In many circumstances a blank
%       will serve just as well. If it won't, then repeat the value.
% \end{enumerate}
%
% Is this just me being pedantic? These last guidelines are
% violated with increasing frequency in published work. To me,
% this just indicates that the typesetting is amatuer.
%
% Anyway, whether or not you wish to follow the minor niceties,
% if you use only the following commands in your formal tables
% your reader will be grateful. (I repeat that 
% the guidelines are not just to
% keep the pedantic happy. Enforced structure of presentation
% enforces structured thought in the first instance.)
%
% \section{Use of the new commands}
%
% \DescribeMacro\toprule
% \DescribeMacro\midrule
% \DescribeMacro\bottomrule
% In the simplest of cases a table begins with a =\toprule=, has
% a single row of column headings, then a dividing rule called
% here a =\midrule=; after the columns of data we finish off with
% a =\bottomrule=. Most book publishers set the =\toprule= and 
% =\bottomrule= heavier (ie thicker, or darker; see notation)
% than the intermediate =\midrule=. However, when tables appear
% in very small typesizes it is sometimes impossible to make this
% distinction, and moreover quite a few journals use all rules of
% the same heaviness. The rule commands here all take a default
% which may be reset within the document (preferably, but not
% necessarily, in the preamble). For the top and bottom rules this
% is =\heavyrulewidth= and for midrules it is =\lightrulewidth=
% (fully described below). In very rare cases where you need to do
% something special, you may use the optional arguments to the rule
% commands which have formal syntax as follows:
% \begin{quote}
%   "\toprule["\meta{wd}"]" \\
%   "\midrule["\meta{wd}"]" \\
%   "\bottomrule["\meta{wd}"]"
% \end{quote}
% where \meta{wd} is a \TeX dimension (for example 1pt, .5em,
% etc.).
%
% All the rule commands here go immediately after the closing
% =\\= of the preceding row (except of course =\toprule=, which
% comes right after the =\tabular{}= command); in other words,
% exactly where plain \LaTeX{} allows =\hline= or =\cline=.
%
% \DescribeMacro\cmidrule
% Of course more often than not we need a rule to extend over
% certain of the columns, for which we need a =\cmidrule= (the
% analogue of \LaTeX's =\cline= command). Generally, this rule
% should not come to the full width of the end columns, and this
% is especially the case when we need to begin a =\cmidrule=
% straight after the end of another one (\LaTeX's =\cline=s crash
% into each other here if you are not extra careful with =\extracolsep=).
% Thus, you will generally want to use the
% optional `trimming' commands, which are =(r)=, =(l)= and =(rl)=
% or =(lr)=, indicated whether the right and/or left ends of the
% rule should be trimmed. Note the exceptional use of parentheses
% instead of braces or brackets for this command, the full syntax
% of which is
% \begin{quote}
%   "\cmidrule["\meta{wd}"]("\meta{trim}"){"$a$--$b$"}"
% \end{quote}
% where again \meta{wd} is an optional rule width command (the
% default here is =\cmidrulewidth=) and the last argument, which
% is not optional, gives the column numbers to be spanned.
%
% An example of the commands in use is given by the code used to
% produce the example table above:
% \begin{verbatim}
% \begin{tabular}{@{}llr@{}} \toprule
% \multicolumn{2}{c}{Item} \\ \cmidrule(r){1-2}
% Animal & Description & Price (\$)\\ \midrule
% Gnat  & per gram  & 13.65 \\
%       & each      & 0.01 \\
% Gnu   & stuffed   & 92.50 \\
% Emu   & stuffed   & 33.33 \\
% Armadillo & frozen & 8.99 \\ \bottomrule
% \end{tabular}
% \end{verbatim}
%
% \DescribeMacro\addlinespace
% Occasionally we want to put an extra space between certain rows
% of a table; for example, before the last row, if this is a
% total (space is better than another =\midrule= here, in my
% opinion). This is simply a matter of inserting
% \begin{quote}
%   "\addlinespace["\meta{wd}"]"
% \end{quote}
% after the =\\= alignment marker. It is not a bad idea to think
% of =\addlinespace= as being a white rule of width \meta{wd}.
% The default space is =\defaultaddspace= which gives rather
% less than a whole line space (such as you could create by using
% =\\ \\= at the end of the line; this is really too much space
% in most cases).
%
% \section{Abuse of the new commands}
%
% Let's face it, nobody can leave well alone, so here are some
% guidelines and extra commands for \TeX perts and meddlers.
%
% The new rule commands are not guaranteed to work with =\hline=
% or =\cline=, although these remain available and unchanged. I
% cannot foresee any reason to want to mix them.
%
% More importantly the rules generated by the new commands are in
% no way guaranteed to connect with verticals generated by ={|}=
% characters in the preamble. This is a feature (see above). You
% should not use vertical rules in tables, period.
%
% \DescribeMacro\morecmidrules
% If you just cannot stop yourself from using a double rule,
% even a construction as bizarre as =\toprule==\bottomrule==\midrule=
% will work without generating an error message (just as you can
% double =\hline=). These rules will be separated by the ordinary
% \LaTeX{} separator =\doublerulesep=. However if your perversion
% is to want double =\cmidrule=s you will need the extra command
% =\morecmidrules= to do so properly, because normally two
% =\cmidrule=s  in a row is a completely sane construction
% calling for two rules on the same `rule row'. Thus in
% \begin{quote}
%   "\cmidrule{1-2}\cmidrule{1-2}"
% \end{quote}
% the second command writes a rule that just overwrites the first
% one; I suppose you wanted
% \begin{quote}
%   "\cmidrule{1-2}\morecmidrules\cmidrule{1-2}"
% \end{quote}
% which gives you a double rule between columns one and two,
% separated by =\cmidrulesep= (note: since a =\cmidrule= is
% generally very light, the ordinary =\doublerulesep= is probably
% too much space). Finish off a whole row of rules before giving the
% =\morecmidrules= command. Note that =\morecmidrules= has no
% effect whatsoever if it does not immediately follow a
% =\cmidrule= (ie it is not a general space-generating command).
%
% \DescribeMacro\specialrule
% Talking of which brings us to the abuse of =\addlinespace= to
% generate weird extra space between rules. Don't do it. (It's
% not actually illegal though.) Instead use
% \begin{quote}
%   "\specialrule{"\meta{wd}"}{"\meta{abovespace}"}{"\meta{belowspace}"}"
% \end{quote}
% where it should be noted all three arguments are mandatory (I
% couldn't be bothered to program in defaults). If you use this
% frequently, you have misunderstood the purpose and content
% of the guidelines given above.
% Technical note: no space is added
% after a preceding rule, but a following rule will generate a
% =\doublerulesep= above itself. Why are you reading this section?
%
% \section{Technical summary of commands}
%
% The new rule commands are valid inside the =tabular= (and in
% fact also =array=) environment, in all versions of \LaTeX{} (you
% must remove the
% \begin{quote}
% 	"\ProvidesPackage{booktabs}"
% \end{quote}
%  line from
% =booktabs.sty= to run in \LaTeX{}2.09 and earlier), and
% fully compatible with the extended array environment of the
% \LaTeX2$\epsilon$ tools package.
%
% The commands follow the standard placement syntax of =\hline=.
% If rule commands are doubled, it is safest to ensure there is
% no space between the commands. (In many circumstances
% violations of this safety rule will give the weird message
% ``=misplaced noalign{=''.) Don't use double rules!
%
% For the present purposes a `rule' is any of =\toprule=,
% =\midrule=, =\bottomrule=, =\cmidrule=, =\specialrule= or
% =\addlinespace=. Note especially the inclusion of
% =\addlinespace= in this list; and the exclusion of =\hline= and
% =\cline=, which will give unpredicatble results if mixed with these.
%
% \begin{quote}
%   "\toprule["\meta{wd}"]"
% \end{quote}
% A rule of width \meta{wd} (default =\heavyrulewidth=) with
% =\belowrulesep= extra vertical space inserted below it (unless
% followed by another rule command, in which case
% =\doublerulesep= vertical space follows).
% \begin{quote}
%   "\midrule["\meta{wd}"]"
% \end{quote}
% A \meta{wd} (default =\lightrulewidth=) rule with
% =\aboverulesep= space above it (unless preceded by another
% rule, from which it will be separated by =\doublerulesep=) and
% with =\belowrulesep= space below it (unless another rule
% follows).
% \begin{quote}
%   "\bottomrule["\meta{wd}"]"
% \end{quote}
% A \meta{wd} (default =\heavyrulewidth=) rule with
% =\aboverulesep= space above it (unless preceded by another
% rule, from which it will be separated by =\doublerulesep=) and
% with =\belowrulesep= space below it (unless another rule
% follows). The extra space below is to make space for table footnotes.
% \begin{quote}
%   "\cmidrule["\meta{wd}"]("\meta{trim}"){"$a$--$b$"}"
% \end{quote}
% A \meta{wd} (default =\cmidrulewidth=) rule with
% =\aboverulesep= space above it (unless following another
% =\cmidrule=, in which case it is on the same vertical alignment;
% or if following any other rule, separated by =\doublerulesep=; or
% if following =\morecmidrules=, separated by =\cmidrulesep=), and
% with =\belowrulesep= below it (unless followed by another
% =\cmidrule=, in which case the following rule is on the same
% vertical alignment; or if followed by =\morecmdirules=, with
% =\cmidrulesep= below it).
%
% The rule spans columns $a$ to $b$. The optional argument
% \meta{trim} which note goes in parentheses if at all, can be
% either =r= for right trimming, =l= for left trimming, or both.
% \begin{quote}
%   "\addlinespace["\meta{wd}"]"
% \end{quote}
% Actually classed as a zero-width rule with no extra 
% space above and with \meta{wd} (default =\defaultaddspace=)
% space below (if another rule follows, this will be separated by
% a further =\doublerulesep=). In practice use this only to add
% space between rows in the body of the table.
% \begin{quote}
%   "\specialrule{"\meta{wd}"}{"\meta{abovespace}"}{"\meta{belowspace}"}"
% \end{quote}
% A \meta{wd} rule (note mandatory argument) with
% \meta{abovespace} above it and \meta{belowspace} below it
% (unless another rule follows, in which case this will be
% separated by a further =\doublerulesep=).
% \begin{quote}
%   "\morecmidrules"
% \end{quote}
% Instructs \LaTeX{} to begin a new row of =\cmidrules=,
% separated from the last by =\cmidrulesep=. Has no effect
% outside this environment.
%
% The default dimensions are
% \begin{quote}
%   "\heavyrulewidth=.08em" \\
%   "\lightrulewidth=0.5em" \\
%   "\cmidrulewidth=0.3em" \\
%   "\belowrulesep=.65ex" \\
%   "\aboverulesep=.4ex" \\
%   "\defaultaddspace=.5em" \\
%   "\cmidrulekern=.25em"
% \end{quote}
% The last of these, =\cmidrulekern=, is the amount by which a
% =\cmidrule= is trimmed at each end indicated in the =()=
% options. In the construction
% \begin{quote}
%   "\cmidrule(r){1-2}\cmidrule(l){3-4}"
% \end{quote}
% there is a total of .5 em separating the two rules. Currently
% the only way to get special effects is to reset =\cmidrulekern=
% as appropriate; the amount of trimming is not available as an
% argument in the current implementation of =\cmidrule=.
%
% The user can change these defaults on the fly by simply
% inserting a command in exactly the same format as above; the
% redefinition will stay in effect for the rest of the document
% or until redefined again.
%
%
% \section{Support for \texttt{firsthline} and
% \texttt{lasthline}}
%
% Yes in a way, but mostly no. Just not applicable. The commands
% here are not about doing neat things with boxes; those are
% tableaux not tables. You do not ever, ever want a formal table
% in the middle of a line of text.
%
% However, if you use the =array.sty= package, the commands are
% not altered by the present code (just as =\hline= and =\cline=
% remain active).
%
% \section{Acknowledgments}
% Hugely indebted of course to DEK and Lamport; the optional
% argument and =\cmidrule=
% stuff especially is filched and adapted from =latex.sty=.
% The documentation driver stuff is stolen wholesale from the
% tools package description =dcolumn.dtx= by David Carlisle.
%
% For beta testing and encouragement ...
%
% \StopEventually
%
% \section{The code}
%
%    The current version is defined at the top of the file looking
%    something like this
%    \begin{macrocode}
%<*package>
\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{booktabs}
        [\filedate\space version\fileversion]
%    \end{macrocode}
%
% First we set up the new dimensions described above:
%    \begin{macrocode}
\newdimen\heavyrulewidth 
\newdimen\lightrulewidth 
\newdimen\cmidrulewidth  
\newdimen\belowrulesep   
\newdimen\aboverulesep   
\newdimen\cmidrulesep    
\newdimen\cmidrulekern   
\newdimen\defaultaddspace
\heavyrulewidth=.08em
\lightrulewidth=.05em
\cmidrulewidth=.03em
\belowrulesep=.65ex
\aboverulesep=.4ex
\cmidrulesep=\doublerulesep
\cmidrulekern=.25em
\defaultaddspace=.5em
%    \end{macrocode}
% And some internal counters of no interest to the end user:
%    \begin{macrocode}
\newcount\rulesflag
\newdimen\@cmidrulewidth
\newcount\@cmidla
\newcount\@cmidlb
\rulesflag=0
%    \end{macrocode}
% which will be described as needed below.
%
% \subsection{Full width rules}
%
% We put the full width rules into a =\noalign{}= group, using a
% dirty trick ("\ifnum=0`}") to fool the parser that the bracket
% count is OK. The bracket really gets closed after all the skipping
% at the end of the =\@endrule= macro.
%
% \begin{macro}{\toprule}
%    \begin{macrocode}
\def\toprule{\noalign{\ifnum0=`}\fi
    \@ifnextchar[{\@toprule}{\@toprule[\heavyrulewidth]}}
%    \end{macrocode}
% This allows for =\toprule='s optional argument; 
% if it has one, it is passed to
% =\@toprule=, otherwise we call this with the default =\heavyrulewidth=.
%
% In the following,
% if =\rulesflag= has been set (to one) we have just done a
% previous rule that has been exceptionally modified to not have
% its normal space below, so we need to put =\doublerulesep=
% before this =\toprule=; then we clear the flag.
%   Note: we can't just always add =\belowrulesep= below a =\toprule=,
%   because there should be =\doublerulesep= between succesive rules.
%   But we could just ban double rules!
%    \begin{macrocode}
\def\@toprule[#1]{\ifnum\rulesflag=1\vskip 
    \doublerulesep\global\rulesflag=0\fi
    \hrule \@height#1\futurelet\@tempa\@endrule}
%    \end{macrocode}
% In the third line above we have put in the rule, and we call
% the closing routine =\@endrules= with =\@tempa= set to the token
% following the rule command in the document.
%    \begin{macrocode}
\def\@endrule{\ifx\@tempa\toprule\global\rulesflag=1%
    \else\ifx\@tempa\midrule\global\rulesflag=1%
    \else\ifx\@tempa\bottomrule\global\rulesflag=1%
    \else\ifx\@tempa\cmidrule\global\rulesflag=1%
    \else\ifx\@tempa\specialrule\global\rulesflag=1%
    \else\ifx\@tempa\addlinespace\global\rulesflag=1%
    \else\vskip \belowrulesep\fi\fi\fi\fi\fi\fi\ifnum0=`{\fi}}
%    \end{macrocode}
% Here if the next command is another 
% rule or linespace (shame on user!) we
% have set the =\rulesflag= to 1 (and added no space); 
% otherwise we have added the proper space below.
% \end{macro}
%
% \begin{macro}{\midrule}
% \begin{macro}{\bottomrule}
% The code is almost the same as for a =\toprule= except for the
% addition of space above.
%
% Note that as far as programming is concerned, a =\bottomrule=
% is just a heavy =\midrule= (but the end user should not think of
% it in this way).
%    \begin{macrocode}
\def\midrule{\noalign{\ifnum0=`}\fi
    \@ifnextchar[{\@midrule}{\@midrule[\lightrulewidth]}}
\def\@midrule[#1]{\ifnum\rulesflag=1\vskip
    \doublerulesep\global\rulesflag=0
    \else\vskip \aboverulesep\fi
    \hrule \@height#1\futurelet\@tempa\@endrule}
\def\bottomrule{\noalign{\ifnum0=`}\fi
    \@ifnextchar[{\@midrule}{\@midrule[\heavyrulewidth]}}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\addlinespace}
% An =\addlinespace= is handled like a zero-width rule with
% no space above and argument (or default) space below.
% Note that a following rule will be added after an {\em additional}
% =\doublerulesep= space. (Users are not encouraged to add space
% before/after rules with =\addlinespace=. If this is needed, they
% should use a =\specialrule=.)
%    \begin{macrocode}
\def\addlinespace{\noalign{\ifnum0=`}\fi
    \@ifnextchar[{\@addspace}{\@addspace[\defaultaddspace]}}
\def\@addspace[#1]{\ifnum\rulesflag=1\global\rulesflag=0\fi
    \vskip #1\futurelet\@tempa\@endrule}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\specialrule}
% This is included with some misgivings as it allows the user to
% do silly things. But a style designer might need this (or a
% modification of it) in times of need.
%
% Note that a following 
% =\toprule= will behave as expected (no extra space above), but
% a =\midrule= or =\bottomrule= will add =\aboverulespace=, whereas a
% following =\cmidrule= will add =\doublerulesep=. Why would you ever
% want to do this anyway?
%    \begin{macrocode}
\def\specialrule#1#2#3{\noalign{
    \ifnum\rulesflag=1\global\rulesflag=0
    \else\vskip #2\fi\hrule \@height#1\vskip #3}}
%    \end{macrocode}
% \end{macro}
%
% \subsection{Special subrules}
%
% \begin{macro}{\cmidrule}
% The =\cmidrule= uses =\rulesflag= in a slightly different way. This
% is (left) set to one if you are in the middle of a row of
% =\cmidrules=, or starting a new one (with =\morecmidrules=).
% Otherwise, when =\rulesflag= is zero, we precede the
% rule with =\aboverulesep=.
%    \begin{macrocode}
\def\cmidrule{\noalign{\ifnum0=`}\fi
    \@ifnextchar[{\@cmidrule}{\@cmidrule[\cmidrulewidth]}}
\def\@cmidrule[#1]{\@ifnextchar({\@@cmidrule[#1]}{\@@cmidrule[#1]()}}
\def\@@cmidrule[#1](#2)#3{\@@@cmidrule[#3]{#1}{#2}}
%    \end{macrocode}
% The above is fiddling around to set defaults for missing optional
% arguments. We also pass to =\@@@cmidrule= in a different order,
% namely =[a-b]=={width required}= ={kerning commands}= (can't
% remember why I did this):
%    \begin{macrocode}
\def\@@@cmidrule[#1-#2]#3#4{\global\@cmidla#1\relax
    \global\advance\@cmidla\m@ne
    \ifnum\@cmidla>0\global\let\@gtempa\@cmidrulea\else
    \global\let\@gtempa\@cmidruleb\fi
    \global\@cmidlb#2\relax
    \global\advance\@cmidlb-\@cmidla
%    \end{macrocode}
% This has set up a switch to call the relevant routine,
% =\@cmidrulea= or =\@cmidruleb=, depending on whether we start
% from column one or not (what a faff).
%    \begin{macrocode}
    \global\@cmidrulewidth=#3
%    \end{macrocode}
% That is, set per default or given argument.
%
% Now we parse the trimming arguments (if there are any):
%    \begin{macrocode}
    \global\let\cmlkern@l\z@ \global\let\cmlkern@r\z@
    \@tfor\@tempa :=#4\do{\global\expandafter\let
        \csname cmlkern@\@tempa\endcsname\cmidrulekern}%
%    \end{macrocode}
% Now insert space above if needed, close the =\noalign=,
% then switch to appropriate rule drawing routine as determined
% above (=\let= to =\@gtempa=):
%    \begin{macrocode}
\ifnum\rulesflag=0\vskip \aboverulesep\fi\ifnum0=`{\fi}\@gtempa
%    \end{macrocode}
% Now open another =\noalign=, and call the closing routine:
%    \begin{macrocode}
    \noalign{\ifnum0=`}\fi\futurelet\@tempa\@xcmidrule}
%    \end{macrocode}
%
% This code (called above) actually draws the rules:
%    \begin{macrocode}
\def\@cmidrulea{\multispan\@cmidla&\multispan\@cmidlb
    \unskip\hskip \cmlkern@l\leaders\hrule \@height\@cmidrulewidth\hfill
    \hskip \cmlkern@r\cr}
\def\@cmidruleb{\multispan\@cmidlb
    \unskip\hskip \cmlkern@l\leaders\hrule \@height\@cmidrulewidth\hfill
    \hskip \cmlkern@r\cr}
%    \end{macrocode}
% Finally, the closing routine. 
% If another =\cmidrule= follows, backspace
% vertical so it will line up, and "\rulesflag=1" will suppress
% adding space above the next. If a =\morecimdrules= follows,
% we add (positive) =\cmidrulesep= (and again set =\rulesflag=
% to one). Otherwise this is the last rule of the current group
% and we can just add =\belowrulesep=.
%
% Finally, we close the =\noalign=.
%    \begin{macrocode}
\def\@xcmidrule{\ifx\@tempa\cmidrule\vskip-\@cmidrulewidth
    \global\rulesflag=1\else
    \ifx\@tempa\morecmidrules\vskip \cmidrulesep
    \global\rulesflag=1\else
    \vskip \belowrulesep\global\rulesflag=0\fi\fi
    \ifnum0=`{\fi}}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\morecmidrules}
% This is really a dummy command; all the work is done above
% within the =\cmidrule= routine. We look one step ahead there
% to see if a =\morecmidrules= follows the current =\cmidrule=,
% and if so set the flag. Otherwise,  =\morecmidrules= itself
% does nothing.
%    \begin{macrocode}
\def\morecmidrules{\noalign{\relax}}
%    \end{macrocode}
% \end{macro}
%
%    \begin{macrocode}
%</package>
%    \end{macrocode}
%
% \Finale
%