TeX - LaTeX Asked by Chris_77 on April 7, 2021
I’ve recently been asked whether the command to remove navigation bars in a Beamer presentation is the longest built-in LaTeX command:
beamertemplatenavigationsymbolsempty
I’ve done some research but couldn’t find anything that comes close to its 36 characters. Neither could I find any discussion of this completely fun trivial fact (although it might be useful to know for some procedural generation applications), so this seems like the right place to start one. The rules are: only the number of characters between the slash symbol and any option symbols (
[
or {
) count, and only commands that are built into the TeX core or commonly used packages and that do not depend on user data (such as those generated by csname
).
We can (sort of) find out.
Any LaTeX “command”—in TeX terminology, the escape character (usually backslash) followed by a control sequence—is put into the TeX program's internal hash table when it is defined. Using LuaTeX, we can look up this hash table directly, with tex.hashtokens
.
documentclass{article}
usepackage{luacode}
begin{document}
begin{luacode}
function string.startswith(s, p) return string.sub(s, 1, string.len(p)) == p end
function string.contains(s, substring) return s:find(substring) ~= nil end
hashed = {}
count = 0
for i,v in pairs (tex.hashtokens()) do
count = count + 1
table.insert(hashed, v)
end
table.sort(hashed, function(a,b) return #a < #b end)
for i, v in ipairs(hashed) do
if not (
v:startswith('<')
or v:contains(' ')
or v:startswith('_')
) then
print(#v, v)
end
end
print(string.format('There are %d entries in the hash table.', count))
end{luacode}
end{document}
When compiled with LuaTeX (need to invoke it with the environment variable hash_extra
set to 0, because of a surprising behaviour/bug in LuaTeX), this prints many lines of output, ending with:
37 peek_charcode_remove_ignore_spaces:NT
37 peek_charcode_remove_ignore_spaces:NF
37 box_autosize_to_wd_and_ht_plus_dp:cnn
37 box_autosize_to_wd_and_ht_plus_dp:Nnn
37 c__text_mathchardef_group_begin_token
37 peek_catcode_remove_ignore_spaces:NTF
37 tex_scriptscriptbaselineshiftfactor:D
38 box_gautosize_to_wd_and_ht_plus_dp:cnn
38 use_none_delimit_by_q_recursion_stop:w
38 box_gautosize_to_wd_and_ht_plus_dp:Nnn
38 peek_charcode_remove_ignore_spaces:NTF
There are 13555 entries in the hash table.
Each of these would be invoked in LaTeX typically with a backslash (the escape character, that indicates to TeX that what follows is a control sequence to be looked up in the hash table), e.g. the last one as peek_charcode_remove_ignore_spaces:NTF
; we don't count the backslash in the character counts above. This is consistent with the question's example of counting beamertemplatenavigationsymbolsempty
as 36 rather than 37 characters.
The output above excluded some entries of the hash table:
The absolute longest entries in the hash table are strings like
<-5.5>"[lmroman5-regular]:+tlig;"<5.5-6.5>"[lmroman6-regular]:+tlig;"<6.5-7.5>"[lmroman7-regular]:+tlig;"<7.5-8.5>"[lmroman8-regular]:+tlig;"<8.5-9.5>"[lmroman9-regular]:+tlig;"<9.5-11>"[lmroman10-regular]:+tlig;"<11-15>"[lmroman12-regular]:+tlig;"<15->"[lmroman17-regular]:+tlig;"
which are some kind of internal font names. So let's exclude everything starting with a <
.
The next longest is the 70-character entry @err@
(ending with 65 spaces); not sure what this is. But let's exclude entries containing spaces.
The next longest are entries like __text_change_case_letterlike_titleonly:nnN
(length 43). Maybe the leading underscore indicates they're “internal” and not intended to be used by end users? Let's exclude those.
That leaves what you see above. The LuaTeX documentation mentions a caveat about tex.hashtokens
:
note that this also reports control sequences that may be unreachable at this moment due to local redefinitions: it is strictly a dump of the hash table.
But there's a bigger caveat, which is the main problem with this question. Namely, a missing definition of “built-in LaTeX command”. One could make a precise definition as “commands built into LaTeX itself”, but that's clearly not what's intended by the question, as it includes the example beamertemplatenavigationsymbolsempty
from Beamer, and also mentions “built into the TeX core or commonly used packages”. (Beamer is a package that is not part of LaTeX itself; it's just a (widely used) package that someone happens to have written, which works with LaTeX and is distributed with TeX distributions like TeX Live / MiKTeX.)
For example, if we add usepackage{tikz}
near the top of the above file, we get different output:
44 pgfmath@operation@pgfmath@bgroup@precedence
44 pgfmath@operation@pgfmath@egroup@precedence
44 pgf@arrows@direct@name@end@{latex}[reversed]
44 pgfqkeysactivatesinglefamilyandfilteroptions
45 pgfkeys@ifexecutehandler@handlefullorexisting
45 pgf@plot@closedcurve@after@initial@presupport
45 pgfmathprintnumber@fixed@styleDEFAULT@DEC@SEP
45 pgfincludeexternalgraphics@read@dpth@line@EOI
45 pgfmathprintnumber@thousand@sep@in@fractional
46 pgfmathroundto@impl@ADD@ONE@ITERATE@gobble@dot
46 ifpgfmathround@impl@PREPERIOD@is@negative@zero
46 pgf@arrows@direct@name@end@{stealth}[reversed]
47 ifpgfmathprintnumber@thousand@sep@in@fractional
47 pgfmathprintnumber@RELATIVE@choice@roundtofixed
48 pgfmathroundto@impl@discard@suffix@zeros@ITERATE
48 pgfmathround@impl@PREPERIOD@is@negative@zerotrue
49 pgfmathprintnumber@fixed@styleDEFAULT@impl@period
49 pgfmathprintnumber@thousand@sep@in@fractionaltrue
49 pgfmathround@impl@PREPERIOD@is@negative@zerofalse
50 pgfmathprintnumber@fixed@styleDEFAULT@DEC@SEP@MARK
50 pgfmath@token@group@pgfmath@bgrouppgfmath@egroup
50 pgfmathprintnumber@thousand@sep@in@fractionalfalse
50 pgfincludeexternalgraphics@read@dpth@line@getfirst
50 pgfmathprintnumber@fixed@styleDEFAULT@THOUSAND@SEP
51 pgfmathprintnumber@fixed@styleDEFAULT@impl@noperiod
52 pgfmathprintnumber@thousand@sep@in@fractional@finish
52 pgfmathprintnumber@RELATIVE@choice@roundtofixed@warn
53 pgfmathprintnumber@thousand@sep@in@fractional@finish@
56 pgfmathprintnumber@fixed@styleDEFAULT@impl@noperiod@NEXT
60 pgfmathprintnumber@fixed@styleDEFAULT@impl@noperiod@printall
61 pgfmathprintnumber@fixed@styleDEFAULT@impl@noperiod@printall@
61 pgfmathprintnumber@fixed@styleDEFAULT@impl@noperiod@printsign
67 pgfmathprintnumber@fixed@styleDEFAULT@impl@noperiod@counteverythird
71 pgfmathprintnumber@fixed@styleDEFAULT@impl@noperiod@printtrailingdigits
There are 24340 entries in the hash table.
Many of the above are names internally generated by the package using csname
. You may want to exclude commands containing @
as they can be input only after makeatletter
, and are probably internal by convention. Still:
39 pgfmathfloatroundmayneedrenormalizetrue
39 pgfkeysactivatefamiliesandfilteroptions
40 pgfmathfloatroundmayneedrenormalizefalse
40 pgfmathfloatparsenumberpendingperiodtrue
40 pgfqkeysactivatefamiliesandfilteroptions
41 pgfmathfloatparsenumberpendingperiodfalse
43 pgfkeysactivatesinglefamilyandfilteroptions
44 pgfqkeysactivatesinglefamilyandfilteroptions
Loading further macros (adding further packages, or usetikzlibrary
etc) will change the output and somewhere there may exist a package that defines longer commands. For example, still excluding ones with @
, with pgfmanual
(suggested by user muzimuzhi Z
in the comments):
38 box_gautosize_to_wd_and_ht_plus_dp:Nnn
38 ifpgfmathfloatparsenumberpendingperiod
38 use_none_delimit_by_q_recursion_stop:w
38 pgfmanualprettyprinternumcollectedargs
38 box_gautosize_to_wd_and_ht_plus_dp:cnn
38 peek_charcode_remove_ignore_spaces:NTF
39 pgfkeysactivatefamiliesandfilteroptions
39 ifpgfmanualprettyprinterfoundterminator
39 pgfmathfloatroundmayneedrenormalizetrue
40 pgfqkeysactivatefamiliesandfilteroptions
40 pgfmathfloatparsenumberpendingperiodtrue
40 pgfmathfloatroundmayneedrenormalizefalse
41 pgfmathfloatparsenumberpendingperiodfalse
41 pgfmanualprettyprinterhandlecollectedargs
41 pgfmanualprettyprinterfoundterminatortrue
42 pgfmanualprettyprinterfoundterminatorfalse
43 pgfkeysactivatesinglefamilyandfilteroptions
44 pgfqkeysactivatesinglefamilyandfilteroptions
45 ifpgfmanualprettyprinterarghasunmatchedbraces
45 pgfmanualprettyprinterhandlecollectedargsVtwo
47 pgfmanualprettyprinterarghasunmatchedbracestrue
48 pgfmanualprettyprinterarghasunmatchedbracesfalse
And as a sanity check, with documentclass{beamer}
instead, we do get the question's beamertemplatenavigationsymbolsempty
and a few longer ones as well (this time I also removed expressions containing -
or underscore or backslash, to keep this output smaller):
36 pgfmathprintnumberskipzeroperiodtrue
36 insertsubsectionnavigationhorizontal
36 beamertemplatenavigationsymbolsframe
36 beamertemplatenavigationsymbolsempty
36 pgfmathpointintersectionoflineandarc
36 beamertemplatesidebarverticalshading
36 pgfpagescurrentpagewillbelogicalpage
36 beamertemplatetransparentcoveredhigh
36 pgfrememberpicturepositiononpagetrue
36 MakeUppercaseUnsupportedInPdfStrings
36 beamertemplatenumberedballsectiontoc
36 MakeLowercaseUnsupportedInPdfStrings
37 useleftsidebarverticalshadingtemplate
37 pgfapproximatenonlineartransformation
37 pgfkeysaddhandleonlyexistingexception
37 pgfhorizontaltransformationadjustment
37 insertbackfindforwardnavigationsymbol
37 beamertemplatesphereminiframeinverted
37 ifpgfmathfloatroundmayneedrenormalize
37 beamertemplatecircleminiframeinverted
37 pgfmathprintnumberskipzeroperiodfalse
37 pgfrememberpicturepositiononpagefalse
38 beamertemplatenumberedcirclesectiontoc
38 beamertemplatesidebarhorizontalshading
38 ifpgfmathfloatparsenumberpendingperiod
38 beamertemplatetransparentcoveredmedium
38 userightsidebarverticalshadingtemplate
38 beamertemplatenumberedsquaresectiontoc
39 beamertemplatenavigationsymbolsvertical
39 pgfkeysactivatefamiliesandfilteroptions
39 useleftsidebarhorizontalshadingtemplate
39 beamertemplatetransparentcoveredhighest
39 beamertemplatetransparentcovereddynamic
39 pgfmathfloatroundmayneedrenormalizetrue
40 pgfqkeysactivatefamiliesandfilteroptions
40 pgfmathfloatroundmayneedrenormalizefalse
40 pgfmathfloatparsenumberpendingperiodtrue
40 userightsidebarhorizontalshadingtemplate
40 beamertemplaterightsidebarlogonavigation
41 pgfmathfloatparsenumberpendingperiodfalse
41 beamertemplatenavigationsymbolshorizontal
43 pgfkeysactivatesinglefamilyandfilteroptions
44 pgfqkeysactivatesinglefamilyandfilteroptions
45 beamertemplatetransparentcovereddynamicmedium
Correct answer by ShreevatsaR on April 7, 2021
This is actually very hard to answer. The LaTeX kernel (very frequently used package ;)) loads expl3
. It has commands like use_none_delimit_by_q_recursion_stop:w
(39 chars).
I don't actually know whether there are longer macro names but many packages do something like
csname module@property@#1endcsname`
and therefore generate macro names often based on user data (e.g. keys in key-value interfaces etc.). Are these built-in? Probably yes, because they are implicitly defined in commonly used packages.
So while I think that thorough investigation will yield very long macro names, without a clear definition of built into
in a language of TeX's kind this question does not have a definitive answer.
Answered by TeXnician on April 7, 2021
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