pTeX: ある fontdef トークンが欧文フォントか和文横組フォントか和文縦組フォントか

20190727-fontdef.tex

\catcode`\@=11

\ifx\@firstoftwo\@undefined
  \def\@firstoftwo#1#2{#1}
\fi
\ifx\@secondoftwo\@undefined
  \def\@secondoftwo#1#2{#2}
\fi

\def\ptexutil@ifjfont#1{\putl@parse@fontdef{#1}%
  \if j\putl@fonttype \expandafter\@firstoftwo
  \else \expandafter\@secondoftwo \fi}
\def\ptexutil@iftfont#1{\putl@parse@fontdef{#1}%
  \if t\putl@fonttype \expandafter\@firstoftwo
  \else \expandafter\@secondoftwo \fi}
\def\ptexutil@ifafont#1{\putl@parse@fontdef{#1}%
  \if a\putl@fonttype \expandafter\@firstoftwo
  \else \expandafter\@secondoftwo \fi}

{\escapechar-1 \xdef\putl@select@font{\string\select\space\string\font\space}}
\def\putl@parse@fontdef#1{%
  \def\reserved@a{#1}%
  \edef\putl@parse@tmp{\meaning#1 \putl@select@font}%
  \expandafter\putl@parse@@fontdef\putl@parse@tmp\@nil}
\expandafter\def\expandafter\putl@parse@@fontdef
  \expandafter#\expandafter1\putl@select@font#2\@nil{%
  \ifx\relax#1\relax \putl@dist@font \else \putl@err@notfontdef \fi}
\def\putl@dist@font{{\reserved@a
  \expandafter\expandafter\expandafter\ifx
  \expandafter\the\expandafter\jfont\reserved@a
    \global\def\putl@fonttype{j}\else
  \expandafter\expandafter\expandafter\ifx
  \expandafter\the\expandafter\tfont\reserved@a
    \global\def\putl@fonttype{t}\else
  \expandafter\expandafter\expandafter\ifx
  \expandafter\the\expandafter\font\reserved@a
    \global\def\putl@fonttype{a}\else
    \global\def\putl@fonttype{n}\fi
  \fi\fi
}}
\def\putl@err@notfontdef{%
  \errhelp{This command cannot be used for non-font.}%
  \errmessage{\expandafter\string\reserved@a\space is not a font}}

\newlinechar`^^J

\font\TEST=min10
\ptexutil@ifjfont\TEST{\TTTT}{\FFFF}
\ptexutil@iftfont\TEST{\TTTT}{\FFFF}

\font\X=tmin10
\ptexutil@iftfont\X{\TTTT}{\FFFF}

\ptexutil@iftfont\nullfont{\TTTT}{\FFFF}
\ptexutil@ifafont\nullfont{\TTTT}{\FFFF}

\def\TEST{\endgroup}
\ptexutil@ifjfont\TEST{\TTTT}{\FFFF}

\ptexutil@ifjfont\putl@select@font{\TTTT}{\FFFF}
\ptexutil@ifafont\relax{\TTTT}{\FFFF}

\catcode`\@=12
\end

texjporg/tex-jp-build#97 を実装する前に，マクロで強引にやろうとしたやつ。