Surprising result with “fontenc” when \detokenize is applied to `-`

Question

Whether \detokenize is applied to - or -- under the fontenc package T1 fonts the results are the same.

\documentclass[border=10pt]{standalone}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\begin{document}

\begin{tabular}{lcl}
Command    & applied to        & result                    \\\hline
Verb       & two minus signs   & \verb=--=                 \\
Detokenize & two minus signs   & \ttfamily\detokenize{--}  \\
Detokenize & one minus sing    & \ttfamily\detokenize{-}   \\
Detokenize & three minus signs & \ttfamily\detokenize{---} \\
\end{tabular}

\end{document}

It's as if \detokenize is allowing some kind of expansion occur before applying its magic to its argument. But I thought that's exactly what it's not supposed to do.

Could someone explain what's happening here? And, why the difference with \verb?

Answer 1

With both xelatex and lualatex I get the same result with or without \detokenize which is as expected as - has catcode 12 by default, so \detokenize just returns the same tokens as its argument in this case. Ligatures are not done via catcode tricks.

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\begin{document}

\begin{tabular}{lcl}
Command    & applied to        & result                    \\\hline
Verb       & two minus signs   & \verb=--=                 \\
Detokenize & two minus signs   & \ttfamily\detokenize{--}  \\
Detokenize & one minus sing    & \ttfamily\detokenize{-}   \\
Detokenize & three minus signs & \ttfamily\detokenize{---} \\
\end{tabular}


\begin{tabular}{lcl}
Command    & applied to        & result                    \\\hline
Verb       & two minus signs   & \verb=--=                 \\
Detokenize & two minus signs   & \detokenize{--}  \\
Detokenize & one minus sing    & \detokenize{-}   \\
Detokenize & three minus signs & \detokenize{---} \\
\end{tabular}



\begin{tabular}{lcl}
Command    & applied to        & result                    \\\hline
Verb       & two minus signs   & \verb=--=                 \\
Detokenize & two minus signs   & \ttfamily{--}  \\
Detokenize & one minus sing    & \ttfamily{-}   \\
Detokenize & three minus signs & \ttfamily{---} \\
\end{tabular}

\begin{tabular}{lcl}
Command    & applied to        & result                    \\\hline
Verb       & two minus signs   & \verb=--=                 \\
Detokenize & two minus signs   & {--}  \\
Detokenize & one minus sing    & {-}   \\
Detokenize & three minus signs & {---} \\
\end{tabular}

\end{document}