+% @asis just yields its argument. Used with @table, for example.
+%
+\def\asis#1{#1}
+
+% @math outputs its argument in math mode.
+%
+% One complication: _ usually means subscripts, but it could also mean
+% an actual _ character, as in @math{@var{some_variable} + 1}. So make
+% _ active, and distinguish by seeing if the current family is \slfam,
+% which is what @var uses.
+{
+ \catcode`\_ = \active
+ \gdef\mathunderscore{%
+ \catcode`\_=\active
+ \def_{\ifnum\fam=\slfam \_\else\sb\fi}%
+ }
+}
+% Another complication: we want \\ (and @\) to output a math (or tt) \.
+% FYI, plain.tex uses \\ as a temporary control sequence (for no
+% particular reason), but this is not advertised and we don't care.
+%
+% The \mathchar is class=0=ordinary, family=7=ttfam, position=5C=\.
+\def\mathbackslash{\ifnum\fam=\ttfam \mathchar"075C \else\backslash \fi}
+%
+\def\math{%
+ \tex
+ \mathunderscore
+ \let\\ = \mathbackslash
+ \mathactive
+ % make the texinfo accent commands work in math mode
+ \let\"=\ddot
+ \let\'=\acute
+ \let\==\bar
+ \let\^=\hat
+ \let\`=\grave
+ \let\u=\breve
+ \let\v=\check
+ \let\~=\tilde
+ \let\dotaccent=\dot
+ $\finishmath
+}
+\def\finishmath#1{#1$\endgroup} % Close the group opened by \tex.
+
+% Some active characters (such as <) are spaced differently in math.
+% We have to reset their definitions in case the @math was an argument
+% to a command which sets the catcodes (such as @item or @section).
+%
+{
+ \catcode`^ = \active
+ \catcode`< = \active
+ \catcode`> = \active
+ \catcode`+ = \active
+ \catcode`' = \active
+ \gdef\mathactive{%
+ \let^ = \ptexhat
+ \let< = \ptexless
+ \let> = \ptexgtr
+ \let+ = \ptexplus
+ \let' = \ptexquoteright
+ }
+}
+
+
+\message{glyphs,}
+% and logos.
+
+% @@ prints an @.
+\def\@{\char64 }
+
+% Used to generate quoted braces. Unless we're in typewriter, use
+% \ecfont because the CM text fonts do not have braces, and we don't
+% want to switch into math.
+\def\mylbrace{{\ifmonospace\else\ecfont\fi \char123}}
+\def\myrbrace{{\ifmonospace\else\ecfont\fi \char125}}
+\let\{=\mylbrace
+\let\}=\myrbrace
+\begingroup
+ % Definitions to produce \{ and \} commands for indices,
+ % and @{ and @} for the aux/toc files.
+ \catcode`\{ = \other \catcode`\} = \other
+ \catcode`\[ = 1 \catcode`\] = 2
+ \catcode`\! = 0 \catcode`\\ = \other
+ !gdef!lbracecmd[\{]%
+ !gdef!rbracecmd[\}]%
+ !gdef!lbraceatcmd[@{]%
+ !gdef!rbraceatcmd[@}]%
+!endgroup
+
+% @comma{} to avoid , parsing problems.
+\let\comma = ,
+
+% Accents: @, @dotaccent @ringaccent @ubaraccent @udotaccent
+% Others are defined by plain TeX: @` @' @" @^ @~ @= @u @v @H.
+\let\, = \ptexc
+\let\dotaccent = \ptexdot
+\def\ringaccent#1{{\accent23 #1}}
+\let\tieaccent = \ptext
+\let\ubaraccent = \ptexb
+\let\udotaccent = \d
+
+% Other special characters: @questiondown @exclamdown @ordf @ordm
+% Plain TeX defines: @AA @AE @O @OE @L (plus lowercase versions) @ss.
+\def\questiondown{?`}
+\def\exclamdown{!`}
+\def\ordf{\leavevmode\raise1ex\hbox{\selectfonts\lllsize \underbar{a}}}
+\def\ordm{\leavevmode\raise1ex\hbox{\selectfonts\lllsize \underbar{o}}}
+
+% Dotless i and dotless j, used for accents.
+\def\imacro{i}
+\def\jmacro{j}
+\def\dotless#1{%
+ \def\temp{#1}%
+ \ifx\temp\imacro \ifmmode\imath \else\ptexi \fi
+ \else\ifx\temp\jmacro \ifmmode\jmath \else\j \fi
+ \else \errmessage{@dotless can be used only with i or j}%
+ \fi\fi
+}
+
+% The \TeX{} logo, as in plain, but resetting the spacing so that a
+% period following counts as ending a sentence. (Idea found in latex.)
+%
+\edef\TeX{\TeX \spacefactor=1000 }
+
+% @LaTeX{} logo. Not quite the same results as the definition in
+% latex.ltx, since we use a different font for the raised A; it's most
+% convenient for us to use an explicitly smaller font, rather than using
+% the \scriptstyle font (since we don't reset \scriptstyle and
+% \scriptscriptstyle).
+%
+\def\LaTeX{%
+ L\kern-.36em
+ {\setbox0=\hbox{T}%
+ \vbox to \ht0{\hbox{%
+ \ifx\textnominalsize\xwordpt
+ % for 10pt running text, \lllsize (8pt) is too small for the A in LaTeX.
+ % Revert to plain's \scriptsize, which is 7pt.
+ \count255=\the\fam $\fam\count255 \scriptstyle A$%
+ \else
+ % For 11pt, we can use our lllsize.
+ \selectfonts\lllsize A%
+ \fi
+ }%
+ \vss
+ }}%
+ \kern-.15em
+ \TeX
+}
+
+% Some math mode symbols.
+\def\bullet{$\ptexbullet$}
+\def\geq{\ifmmode \ge\else $\ge$\fi}
+\def\leq{\ifmmode \le\else $\le$\fi}
+\def\minus{\ifmmode -\else $-$\fi}
+
+% @dots{} outputs an ellipsis using the current font.
+% We do .5em per period so that it has the same spacing in the cm
+% typewriter fonts as three actual period characters; on the other hand,
+% in other typewriter fonts three periods are wider than 1.5em. So do
+% whichever is larger.
+%
+\def\dots{%
+ \leavevmode
+ \setbox0=\hbox{...}% get width of three periods
+ \ifdim\wd0 > 1.5em
+ \dimen0 = \wd0
+ \else
+ \dimen0 = 1.5em
+ \fi
+ \hbox to \dimen0{%
+ \hskip 0pt plus.25fil
+ .\hskip 0pt plus1fil
+ .\hskip 0pt plus1fil
+ .\hskip 0pt plus.5fil
+ }%
+}
+
+% @enddots{} is an end-of-sentence ellipsis.
+%
+\def\enddots{%
+ \dots
+ \spacefactor=\endofsentencespacefactor
+}
+
+% @point{}, @result{}, @expansion{}, @print{}, @equiv{}.
+%
+% Since these characters are used in examples, they should be an even number of
+% \tt widths. Each \tt character is 1en, so two makes it 1em.
+%
+\def\point{$\star$}
+\def\arrow{\leavevmode\raise.05ex\hbox to 1em{\hfil$\rightarrow$\hfil}}
+\def\result{\leavevmode\raise.05ex\hbox to 1em{\hfil$\Rightarrow$\hfil}}
+\def\expansion{\leavevmode\hbox to 1em{\hfil$\mapsto$\hfil}}
+\def\print{\leavevmode\lower.1ex\hbox to 1em{\hfil$\dashv$\hfil}}
+\def\equiv{\leavevmode\hbox to 1em{\hfil$\ptexequiv$\hfil}}
+
+% The @error{} command.
+% Adapted from the TeXbook's \boxit.
+%
+\newbox\errorbox
+%
+{\tentt \global\dimen0 = 3em}% Width of the box.
+\dimen2 = .55pt % Thickness of rules
+% The text. (`r' is open on the right, `e' somewhat less so on the left.)
+\setbox0 = \hbox{\kern-.75pt \reducedsf error\kern-1.5pt}
+%
+\setbox\errorbox=\hbox to \dimen0{\hfil
+ \hsize = \dimen0 \advance\hsize by -5.8pt % Space to left+right.
+ \advance\hsize by -2\dimen2 % Rules.
+ \vbox{%
+ \hrule height\dimen2
+ \hbox{\vrule width\dimen2 \kern3pt % Space to left of text.
+ \vtop{\kern2.4pt \box0 \kern2.4pt}% Space above/below.
+ \kern3pt\vrule width\dimen2}% Space to right.
+ \hrule height\dimen2}
+ \hfil}
+%
+\def\error{\leavevmode\lower.7ex\copy\errorbox}
+