I don't seem to be able to capitalize a letter that has been assigned to \let.
\let\zTest=t
\uppercase{\zTest} % still small
ADDENDUM: I've tried \def\zTest{t} just now and it didn't work either (but \uppercase{t} works).
3 Answers
\uppercase and \lowercase
- do only apply to explicit character tokens.
- do not trigger expansion after finding
- either the left brace
{of the⟨balanced text⟩that is to be uppercased/lowercased. - or the single not-brace-nested unexpandable non-
⟨filler⟩-token that is to be uppercased/lowercased. (⟨filler⟩denotes a sequence of\relaxand/or explicit/implicit spaces.)
- either the left brace
When using \csname..\endcsname instead of using the control-word-token directly, you can probably do somehing like this:
\let\zTest=t
\let\ZTEST=T
\let\ztest=t
\def\Ztest{t}
% \zTest and \ZTEST and \ztest are implicit character tokens.
% Let`s use uppercased/lowercased \csname..\endcsname for selecting
% which implicit character token to use:
\csname zTest\endcsname
\uppercase{\csname zTest\endcsname}%
\lowercase{\csname zTest\endcsname}%
% \Ztest is a macro, expanding to explicit character token "t".
% You can use \expandafter for triggering "toplevel-expansion"
% while \uppercase/\lowercase still searches the "{" that
% marks the begin of the balanced text:
\Ztest
\uppercase\expandafter{\Ztest}%
\lowercase\expandafter{\Ztest}%
% With more recent TeX-engines, where \expanded is available,
% you can do:
% \lowercase\expandafter{\expanded{\Ztest}}%
% "toplevel-expansion" of \expanded<general text> will deliver
% "total expansion" of the content of the <general text>'s
% <balanced text>
\bye
answered Nov 17, 2019 at 16:40
The following is a macro that is able to uppercase a let token if it was let to a letter (e.g., with \let\foo=t assuming standard category codes). It does so by first checking whether the magic tokens the letter are the start of the meaning of the passed in token, and then grabs the letter following it and uppercases that, if the meaning doesn't seem to be a letter then the input is output. The test is only applied to the first token of the input, but it is not checked whether the input is only a single token (so \uppercaselettoken{t more stuff} would see that t is a letter but passes more stuff to \uppercase, too. So this is only a proof-of-concept not a stable implementation.
\documentclass[]{article}
\let\foo=t
\makeatletter
\def\uppercaselettoken@ifletter#1%
{%
\def\uppercaselettoken@ifletter##1#1##2\end
{%
\if\relax\detokenize{##2}\relax
\expandafter\@secondoftwo
\else
\if\relax\detokenize{##1}\relax
\expandafter\@firstoftwo
\else
\expandafter\@secondoftwo
\fi
{\expandafter\@firstoftwo}
{\expandafter\@secondoftwo}%
\fi
}%
\def\uppercaselettoken@letter#1##1\end{\uppercase{##1}}%
}
\expandafter\uppercaselettoken@ifletter\expandafter{\detokenize{the letter }}
\long\edef\uppercaselettoken@#1#2%
{%
\noexpand\uppercaselettoken@ifletter#1\detokenize{the letter }\noexpand\end
{%
\noexpand\uppercaselettoken@letter#1\noexpand\end
}%
{#2}% not a letter, no uppercasing
}
\newcommand\uppercaselettoken[1]
{%
\expandafter\uppercaselettoken@\expandafter{\meaning#1}{#1}%
}
\makeatother
\usepackage{unravel}
\begin{document}
\uppercaselettoken{\foo}
\uppercaselettoken{t}% works too
\end{document}
-
-
1@bp2017 well, we have to teach TeX something which was originally not meant to be done, so yes, this tends to be complicated.– SkillmonNov 17, 2019 at 17:12
-
@JosephWright not sure whether it should be part of
\tl_upper_case:n, but one could define a variant (something like\tl_upper_case_e:n) which does this. It's your choice :)– SkillmonNov 17, 2019 at 17:13 -
I sometimes use implicit characters and/or
\charin situations where uppercasing/lowercasing of initials and shortcuts of names and the like is to be prevented.. ;-> Nov 17, 2019 at 17:45
While it is possible to implement something that interrogates the meaning of unexpandable tokens, recognises implicit characters defined by \let and look up their upper case form, there are very few reasons to get into that situation, using \def (or \renewcommand) is the documented LaTeX interface and is essentially trivial to make work as you just have to expand the macros before uppercasing, and it works out of the box using LaTeX:
\documentclass{article}
\begin{document}
\let\zza=a
\let\zzb=b
\let\zzc=c
1 \MakeUppercase{\zza\zzb\zzc}
\renewcommand\zza{a}
\renewcommand\zzb{b}
\renewcommand\zzc{c}
2 \MakeUppercase{\zza\zzb\zzc}
\end{document}
answered Nov 17, 2019 at 18:34
\expandafter\uppercase\expandafter{\expanded{<stuff>}}, that would work with<stuff>being letters and macros defined using\newcommandor\def, but not for\let.\uppercaseand\lowercaseonly act on explicit character tokens. Implicit character tokens and macros expanding to character tokens are not touched. An character token produced with\letdoesn't have a\uccode(or\lccode) for\uppercaseto do its thing. Try\showthe\uccode`tand then\showthe\uccode`\zTest(the latter raises an error).\let, if you are prepared to normalise the charcode of{/}.\uppsercasedoes no expansion: when you use\def, the macro token is not affected as it's not a char\UD@CheckWhetherNull,\UD@CheckWhetherBrace,\UD@CheckWhetherLeadingSpacein my answer to the question "How do I pad a string argument to a macro to a set length string" might be of interest. ;-)