parse: add AMS lowercase-greek variants \varkappa and \digamma - #4
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An unknown control sequence in the math layer drops the WHOLE equation group, so a single missing symbol silently deletes real content. \varkappa was absent from the greek table though \kappa and every other var-variant (\varphi, \varrho, \vartheta, \varpi, \varsigma, \varepsilon) were present; on one arXiv article (2606.18084) it occurs 12 times and dropped two display groups. amssymb defines exactly two lowercase-greek variants beyond the standard block: \varkappa (ϰ U+03F0) and \digamma (ϝ U+03DD). Add both as clsOrd. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
tannevaled
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Aug 31, 2026
Three of the commands the go-tex/engine corpus reports as dropped formulas live
here, not in the engine.
\triangleleft and \triangleright were missing. They are BINARY operators at U+25C1
and U+25B7 — unicode-math-table.tex:704/694, and fontmath.ltx:264-265 declares both
\mathbin — and they are not the ⊲ ⊳ of \vartriangleleft/right already in the table,
which amssymb makes relations: the two pairs differ in glyph and in spacing. 98
dropped formulas over the arXiv corpus.
\genfrac{left}{right}{thickness}{style}{num}{den} is amsmath's generalised
fraction (amsmath.sty:245-250):
\edef\@tempb{\@nx\@genfrac\@mathstyle{#4}%
\csname @@\ifx @#3@over\else above\fi
\ifx\@tempa\@empty \else withdelims\fi\endcsname}
so an EMPTY thickness means \over — the font's own rule — and any other means
\above that thickness, 0pt being no rule at all. That is how \binom itself is
defined: \genfrac()\z@{} (amsmath.sty:240). The style argument is TeX's digit: 0
display, 1 text, 2 script, 3 scriptscript, empty keeping the style in force. Both
real uses in the corpus are the delimited no-rule form — a q-binomial written
\genfrac[]{0pt}{}{n}{k} and \genfrac{\{}{\}}{0pt}{} — and 88 formulas were dropped
for it. The delimiters arrive UNBRACED there, as TeX takes single tokens for
arguments, which readOptionalDelim handles beside {} for "no delimiter this side".
\z@ needs its own note: this parser has no catcodes, so amsmath's own spelling of
zero arrives as \z and @, and read as \z alone it would draw a rule where the
binomial wants none. The @ that follows a control word is absorbed with it.
Documented reduction: a non-zero explicit thickness draws the font's rule rather
than that exact width, since fraction() takes its thickness from the font's MATH
table.
tannevaled
added a commit
that referenced
this pull request
Aug 31, 2026
Three of the commands the go-tex/engine corpus reports as dropped formulas live
here, not in the engine.
\triangleleft and \triangleright were missing. They are BINARY operators at U+25C1
and U+25B7 — unicode-math-table.tex:704/694, and fontmath.ltx:264-265 declares both
\mathbin — and they are not the ⊲ ⊳ of \vartriangleleft/right already in the table,
which amssymb makes relations: the two pairs differ in glyph and in spacing. 98
dropped formulas over the arXiv corpus.
\genfrac{left}{right}{thickness}{style}{num}{den} is amsmath's generalised
fraction (amsmath.sty:245-250):
\edef\@tempb{\@nx\@genfrac\@mathstyle{#4}%
\csname @@\ifx @#3@over\else above\fi
\ifx\@tempa\@empty \else withdelims\fi\endcsname}
so an EMPTY thickness means \over — the font's own rule — and any other means
\above that thickness, 0pt being no rule at all. That is how \binom itself is
defined: \genfrac()\z@{} (amsmath.sty:240). The style argument is TeX's digit: 0
display, 1 text, 2 script, 3 scriptscript, empty keeping the style in force. Both
real uses in the corpus are the delimited no-rule form — a q-binomial written
\genfrac[]{0pt}{}{n}{k} and \genfrac{\{}{\}}{0pt}{} — and 88 formulas were dropped
for it. The delimiters arrive UNBRACED there, as TeX takes single tokens for
arguments, which readOptionalDelim handles beside {} for "no delimiter this side".
\z@ needs its own note: this parser has no catcodes, so amsmath's own spelling of
zero arrives as \z and @, and read as \z alone it would draw a rule where the
binomial wants none. The @ that follows a control word is absorbed with it.
Documented reduction: a non-zero explicit thickness draws the font's rule rather
than that exact width, since fraction() takes its thickness from the font's MATH
table.
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An unknown control sequence in the math layer drops the whole equation group, so a single missing symbol silently deletes real content.
\varkappawas absent from the greek table even though\kappaand every other var-variant (\varphi,\varrho,\vartheta,\varpi,\varsigma,\varepsilon) were present. On one arXiv article (2606.18084)\varkappaoccurs 12 times and dropped two display groups.amssymbdefines exactly two lowercase-greek variants beyond the standard block:\varkappa(ϰ U+03F0) and\digamma(ϝ U+03DD). Both added asclsOrd.TestAddedSymbolsgains\varkappa,\digamma, and combinations; full suite green.