Would the redefinition of \k and \H cause trouble?

Question

In my current document, the commands \k and \H are defined to be \PU-cmd\k\Pu\k and \PU-cmd\H\Pu\H, which seems to be part of the package hyperref. However, for the convenience, I redefined them as follows:

\def\k{\Bbbk}
\def\H{\mathbb{H}}

My question is, would these redefinitions cause serious trouble? It seems fine in my document, but I'm afraid if I have broken some important internal commands and the retribution shall come sooner or later.

Untested: You can use \newcommand instead of \def. If the comment already exists, then you will get sn error. — Dr. Manuel Kuehner, Apr 04 '22 at 13:59
@Dr.ManuelKuehner I already know that these commands exist, and that's why I'm asking if it is safe to re-define them. — Jinwen, Apr 04 '22 at 14:02
@marquinho Thank you this! Knowing that \k and \H are diacritics, I think it would be safe (for me) to redefine them, as I'm using Unicode engines and can type in the accented letters directly when needed. — Jinwen, Apr 04 '22 at 14:07
[EDIT: sorry for deleting my former comment!] Those are standard LaTeX diacritics, aren't they? \H is a long Hungarian umlaut as in "ő" and \k is a Polish ogonek as in "ą" (source). hyperref does change the encoding to PU, for use in a PDF, but not the meaning. So redefining them wouldn't break hyperref, if you never use those commands for diacritics — marquinho, Apr 04 '22 at 14:07
They aren't commands specific to hyperref, the accents are defined without them too, hyperref only adds its encoding. I wouldn't redefine them. These commands are standard LaTeX commands and you can't know if some command from some package internally uses \k or \H to produce an accent (it doesn't matter if you use an unicode engine or not). — Ulrike Fischer, Apr 04 '22 at 14:15
When your bibliography cites a paper by “Erdős and Szczęsny” you'll know why redefining \k and \H is a bad idea. Using \kk and \HH is even more semantic, besides avoiding the problem of redefinition. — egreg, Apr 04 '22 at 15:33
Crosslink to related question: macros - How to redefine one-letter commands? - TeX - LaTeX Stack Exchange Short names for macros - TeX - LaTeX Stack Exchange — user202729, Nov 05 '22 at 09:30

score 2 · Accepted Answer · answered Apr 04 '22 at 15:42

2

When you cite a paper by “Erdős and Szczęsny”, you'll know why redefining \k and \H is a bad idea.

\begin{filecontents*}{\jobname.bib}
@article{test,
  author={Erdős, P. and Szczęsny, W.},
  title={Title},
  journal={Journal},
  year={2022},
}
\end{filecontents*}
\documentclass{article}
\usepackage{amsmath,amssymb}
\renewcommand\k{\Bbbk}
\renewcommand\H{\mathbb{H}}
\begin{document}
$\k+\H$ \cite{test}
\bibliographystyle{plain}
\bibliography{\jobname}
\end{document}

The console after running LaTeX and BibTeX and LaTeX again:

! LaTeX Error: \mathbb allowed only in math mode.
See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...
l.4 P.~Erdő
            s and W.~Szczęsny.
?
! Missing $ inserted.
<inserted text>
                $
l.4 P.~Erdős and W.~Szczę
                           sny.

answered Apr 04 '22 at 15:42

egreg

1,121,712

It is not bad idea to redefine sort control sequences at user level. It is bad idea to use them in laTeX as an internal control sequences. Moreover, it is only problem with old LaTeX, non-unicode LaTeX and non-Unicode Bibtex. With Unicode-ready software this problem is not occur. – wipet Apr 04 '22 at 15:57
@wipet Uh? Try and redefine \tenrm in plain TeX. Or \box. The latter is a very nice name for my command, isn't it? – egreg Apr 04 '22 at 16:18
Try to redefine \box or \fi or whatever in OpTeX. Nothing horrible happens. OpTeX will work without problems. – wipet Apr 04 '22 at 16:42
@wipet That's completely irrelevant. LaTeX users may not want to use XeTeX or LuaTeX and they may need to input Erd\H{o}s because they are not required to know how to use Unicode input. And there are thousands (or millions) of documents that need to be typeset without having to change them. That's not so small a difference, is it? – egreg Apr 04 '22 at 17:21
Please allow me to ask one more question, what if I define \k and \H to be my meaning in math mode while keep the original meaning in text mode, using \mode_if_math:TF? – Jinwen Apr 05 '22 at 20:57
@Jinwen It should work, but I wouldn't recommend it: uselessly confusing. I stand with my opinion that \kk and \HH are more semantic. – egreg Apr 05 '22 at 20:58
@egreg OK, thank you, that is indeed a good suggestion. – Jinwen Apr 05 '22 at 21:02

Would the redefinition of \k and \H cause trouble?

1 Answers1