TeX：\if の抜き打ちテストを実際に実行してみる

ifquiz.tex

\countdef\QN=255 \QN=0
\def\TEST#1{\advance\QN1 \immediate\write16
  {\the\QN. #1True\else False\fi}}

% preconditions
\let\a=a
\let\b=a
\def\c{c}
\chardef\d=`d
\let\primA\indent
\chardef\chardefA=42
\newcount\countA \countA=42
\def\macroA{42}
\def\empty{}
\let\X\relax
\catcode`\X=13 \def X{c}
\catcode`\Y=13 \let Y=c
\catcode`\Z=13 \let Z\advance
\catcode`\&=13 \let &\expandafter
\catcode`\?=13 \let ?\undefinedA

% the tests
\TEST{\if a\a}
\TEST{\if b\b}
\TEST{\if \a\b}
\TEST{\if 42}
\TEST{\if c\c}
\TEST{\if ""}
\TEST{\if \empty{}}
\TEST{\if \indent\noindent}
\TEST{\if \countA\chardefA}
\TEST{\if \empty\macroA}
\TEST{\if a\noexpand\a}
\TEST{\if b\noexpand\b}
\TEST{\if c\noexpand\c}
\TEST{\if \primA\noexpand\macroA}
\TEST{\if \noexpand\empty\noexpand\macroA}
\TEST{\if \noexpand'\string'}
\TEST{\if \noexpand\undefinedA\noexpand\undefinedB}
\TEST{\if \noexpand$\relax}
\TEST{\if \noexpand\macroA\countA}
\TEST{\if \noexpand\c\noexpand\undefinedA}
\TEST{\if \noexpand\undefinedB\noexpand\a}
\TEST{\if d\d}
\TEST{\if XY}
\TEST{\if \string X\noexpand X}
\TEST{\if \noexpandY\stringY}
\TEST{\if \noexpandX\relax}
\TEST{\if \noexpandX\c}
\TEST{\if \noexpandX\noexpand\c}
\TEST{\if \noexpandX\chardefA}
\TEST{\if \noexpandYc}
\TEST{\if \noexpandY\primA}
\TEST{\if \noexpandY\string c}
\TEST{\if \noexpandY\countA}
\TEST{\if \noexpandZ\multiply}
\TEST{\if \noexpandZ\noexpand\undefinedA}
\TEST{\if \noexpandZ\stringZ}
\TEST{\if \noexpand&\noexpand\futurelet}
\TEST{\if \noexpand&\noexpand\undefinedA}
\TEST{\if \noexpand&\string&}
\TEST{\if \noexpand?\noexpand\undefinedB}
\TEST{\if \noexpandX\noexpandY}
\TEST{\if \noexpand?\noexpand&}

% done
\csname stop\endcsname % for LaTeX
\end

参照→ じゃあ \if の抜き打ちテストやるぞー ― マクロツイーター