Maths fonts, symbol lookup and accessible equations

A short document with two formulas passed the PDF/UA-2 check of veraPDF twice: once with MathML attached to both formulas and once with none at all. A validator checks rules, not whether a listener can follow x over 2a, and the font, the symbols and the description of every equation are the author’s choices.

Below you will choose an OpenType maths font in LaTeX and in Typst, find the name or command of any symbol, build a tagged LaTeX PDF whose formulas carry MathML, give every Typst equation the alternative text that PDF/UA-1 export demands, and see what a copy, a validator and a screen reader each get. Every result on this page comes from files built with TeX Live 2026 and Typst 0.15.1 and checked with veraPDF 1.30.

An OpenType maths font carries the shapes and the layout rules

Typst’s maths reference says that only special OpenType maths fonts are suitable for typesetting maths. Such an OpenType maths fontOpenType maths font: An OpenType font with a MATH table: the shapes of maths symbols in several sizes and the layout values an engine needs, such as how far to raise a superscript. Latin Modern Math and STIX Two Math are examples. holds the shapes of thousands of symbols and a table of layout values, such as how far a superscript is raised and how thick a fraction bar is, which the engine reads instead of guessing. Here is one formula, set by Typst in four of them:

The four rows differ in weight and width, but every one has its limits above and below the sum and its fractions stacked, because each font brings its own layout values. In LaTeX, the unicode-math package loads such fonts under LuaLaTeX and XeLaTeX with \setmathfont{STIX Two Math}, and its manual says that Latin Modern Math is loaded automatically when you choose none. In Typst, a show-set rule changes the font of every equation, #show math.equation: set text(font: "STIX Two Math"). The session builds one formula with three fonts in LuaLaTeX and lists what the PDFs embed, then looks at Typst’s defaults and at the figure above:

% LuaLaTeX: unicode-math sets the maths in the OpenType font named by \mathfontname, which the session passes on the
% command line, so that one file builds with each font.
\documentclass{article}
\usepackage{unicode-math}
\setmathfont{\mathfontname}
\pagestyle{empty}
\begin{document}
\[
  \sum_{n=1}^{\infty} \frac{1}{n^2} = \frac{\pi^2}{6}
\]
\end{document}

Typst's default text font with its default maths font: $sum_(n=1)^oo 1 / n^2 = pi^2 / 6$.

// The lesson's figure of four maths fonts (diagrams/fonts.src.svg): one formula per font, with the font's name.
// Built with typst compile --format svg and the fonts of TeX Live's texmf-dist/fonts/opentype/public folders,
// then svg_theme.py.
#set page(width: auto, height: auto, margin: 4pt)
#set text(font: "New Computer Modern")
#grid(
  columns: 2,
  column-gutter: 8pt,
  row-gutter: 4pt,
  align: (right + horizon, left + horizon),
  ..("New Computer Modern Math", "Latin Modern Math", "STIX Two Math", "Libertinus Math")
    .map(font => (
      text(size: 7pt, font),
      {
        show math.equation: set text(font: font)
        $ sum_(n=1)^oo 1 / n^2 = pi^2 / 6 $
      },
    ))
    .flatten(),
)

from session import files, run

# fonts.tex built with three OpenType maths fonts from the TeX tree, which LuaLaTeX finds by name: each run defines
# \mathfontname on the command line before it reads the file. pdffonts lists the fonts a PDF embeds. Then Typst: its
# defaults, and figure.typ, which finds the same fonts through --font-path.
files("fonts/fonts.tex", "fonts/default.typ", "fonts/figure.typ")
run("""
lualatex -interaction=nonstopmode -halt-on-error -jobname=latin '\\def\\mathfontname{Latin Modern Math}\\input{fonts.tex}' | grep -E "Warning|Output written"
lualatex -interaction=nonstopmode -halt-on-error -jobname=stix '\\def\\mathfontname{STIX Two Math}\\input{fonts.tex}' | grep -E "Warning|Output written"
lualatex -interaction=nonstopmode -halt-on-error -jobname=libertinus '\\def\\mathfontname{Libertinus Math}\\input{fonts.tex}' | grep -E "Warning|Output written"
pdffonts stix.pdf
typst compile default.typ
pdffonts default.pdf
typst fonts | grep -i math
typst compile --font-path "$(kpsewhich -var-value TEXMFDIST)/fonts/opentype/public" figure.typ
pdffonts figure.pdf
""")

$ lualatex -interaction=nonstopmode -halt-on-error -jobname=latin '\def\mathfontname{Latin Modern Math}\input{fonts.tex}' | grep -E "Warning|Output written"
Output written on latin.pdf (1 page, 5285 bytes).
$ lualatex -interaction=nonstopmode -halt-on-error -jobname=stix '\def\mathfontname{STIX Two Math}\input{fonts.tex}' | grep -E "Warning|Output written"
Output written on stix.pdf (1 page, 5129 bytes).
$ lualatex -interaction=nonstopmode -halt-on-error -jobname=libertinus '\def\mathfontname{Libertinus Math}\input{fonts.tex}' | grep -E "Warning|Output written"
Output written on libertinus.pdf (1 page, 4957 bytes).
$ pdffonts stix.pdf
name                                 type              encoding         emb sub uni object ID
------------------------------------ ----------------- ---------------- --- --- --- ---------
DTBZRU+STIXTwoMath-Regular           CID Type 0C       Identity-H       yes yes yes      4  0
CANSYA+STIXTwoMath-Regular           CID Type 0C       Identity-H       yes yes yes      5  0
$ typst compile default.typ
$ pdffonts default.pdf
name                                 type              encoding         emb sub uni object ID
------------------------------------ ----------------- ---------------- --- --- --- ---------
FACAPN+LibertinusSerif-Regular-Identity-H CID Type 0C       Identity-H       yes yes yes      9  0
XISUDI+NewCMMath-Book-Identity-H     CID Type 0C       Identity-H       yes yes yes     12  0
$ typst fonts | grep -i math
New Computer Modern Math
$ typst compile --font-path "$(kpsewhich -var-value TEXMFDIST)/fonts/opentype/public" figure.typ
$ pdffonts figure.pdf
name                                 type              encoding         emb sub uni object ID
------------------------------------ ----------------- ---------------- --- --- --- ---------
EDHZGX+NewCM10-Regular-Identity-H    CID Type 0C       Identity-H       yes yes yes     24  0
JNDSZR+NewCMMath-Book-Identity-H     CID Type 0C       Identity-H       yes yes yes     27  0
SAMQQR+LatinModernMath-Regular-Identity-H CID Type 0C       Identity-H       yes yes yes     30  0
PESKJC+STIXTwoMath-Regular-Identity-H CID Type 0C       Identity-H       yes yes yes     33  0
UGNCRR+LibertinusMath-Regular-Identity-H CID Type 0C       Identity-H       yes yes yes     36  0

LuaLaTeX found STIX Two Math in the TeX tree by its name and embedded only that font for the formula. Typst’s own default pairs two families: its text font is Libertinus Serif, but its maths font is New Computer Modern Math, the only maths font typst fonts listed. The maths font that matches Libertinus Serif is Libertinus Math, which TeX Live installs: pointed at TeX Live’s OpenType folder with --font-path, Typst found all four maths fonts of the figure.

Symbols are found by name, or typed as Unicode characters

Every symbol has a name in each system: \leq and lt.eq for ≤, \infty and infinity for ∞. To find a name you do not know, LaTeX has the Comprehensive LaTeX Symbol List on CTAN, which lists over 25,000 symbols in tables organised by topic and package, and unicode-math ships unimath-symbols.pdf, a listing of every maths symbol it defines. Typst’s symbol reference names its general symbols, and its maths reference says variants are selected by appending a modifier, such as .not or .eq. This Typst file builds a table by looking twenty names up, so it cannot list a name that Typst does not know:

// Twenty symbols with their Typst names and LaTeX commands. Each row looks its symbol up by name, sym.<name>, and
// prints the character and its code point, so the table cannot list a name that Typst does not have.
#set page(width: auto, height: auto, margin: 8pt)
#let pairs = (
  ("alpha", "\\alpha"), ("pi", "\\pi"), ("Delta", "\\Delta"), ("plus.minus", "\\pm"),
  ("times", "\\times"), ("dot.op", "\\cdot"), ("lt.eq", "\\leq"), ("gt.eq", "\\geq"),
  ("eq.not", "\\neq"), ("approx", "\\approx"), ("in", "\\in"), ("subset", "\\subset"),
  ("infinity", "\\infty"), ("partial", "\\partial"), ("nabla", "\\nabla"), ("sum", "\\sum"),
  ("integral", "\\int"), ("arrow.r", "\\to"), ("RR", "\\mathbb{R}"), ("dots.h", "\\ldots"),
)
#let code(ch) = {
  let hex = upper(str(ch.to-unicode(), base: 16))
  "U+" + "0" * calc.max(0, 4 - hex.len()) + hex
}
#table(
  columns: 4,
  [Symbol], [Typst name], [LaTeX command], [Code point],
  ..pairs
    .map(((name, latex)) => {
      let ch = str(eval("sym." + name))
      (text(font: "New Computer Modern Math", ch), raw(name), raw(latex), code(ch))
    })
    .flatten(),
)

\documentclass{article}
\begin{document}
Typed as characters: $α ≤ β$.
\end{document}

% LuaLaTeX with unicode-math: maths characters may be typed directly.
\documentclass{article}
\usepackage{unicode-math}
\begin{document}
Typed as characters: $α ≤ β$.
\end{document}

from session import files, run

# The table of twenty symbols that symbols.typ builds by looking each name up, read back with pdftotext; then the
# same two Greek letters typed straight into maths, in pdfLaTeX and in LuaLaTeX with unicode-math.
files("symbols/symbols.typ", "symbols/unicode.tex", "symbols/unicode-lua.tex")
run("""
typst compile symbols.typ
pdftotext -layout symbols.pdf - | head -21
!pdflatex -interaction=nonstopmode -halt-on-error unicode.tex > /dev/null
grep -E -A1 "^! LaTeX Error" unicode.log
lualatex -interaction=nonstopmode -halt-on-error unicode-lua.tex | grep -E "Warning|Output written"
pdftotext unicode-lua.pdf - | head -1
""")

$ typst compile symbols.typ
$ pdftotext -layout symbols.pdf - | head -21
Symbol Typst name LaTeX command Code point
α      alpha        \alpha       U+03B1
π      pi           \pi          U+03C0
Δ      Delta        \Delta       U+0394
±      plus.minus   \pm          U+00B1
×      times        \times       U+00D7
⋅      dot.op       \cdot        U+22C5
≤      lt.eq        \leq         U+2264
≥      gt.eq        \geq         U+2265
≠      eq.not       \neq         U+2260
≈      approx       \approx      U+2248
∈      in           \in          U+2208
⊂      subset       \subset      U+2282
∞      infinity     \infty       U+221E
∂      partial      \partial     U+2202
∇      nabla        \nabla       U+2207
∑      sum          \sum         U+2211
∫      integral     \int         U+222B
→      arrow.r      \to          U+2192
ℝ      RR           \mathbb{R}   U+211D
…      dots.h       \ldots       U+2026
$ pdflatex -interaction=nonstopmode -halt-on-error unicode.tex > /dev/null
[exit status 1]
$ grep -E -A1 "^! LaTeX Error" unicode.log
! LaTeX Error: Unicode character α (U+03B1)
               not set up for use with LaTeX.
$ lualatex -interaction=nonstopmode -halt-on-error unicode-lua.tex | grep -E "Warning|Output written"
Output written on unicode-lua.pdf (1 page, 5794 bytes).
$ pdftotext unicode-lua.pdf - | head -1
Typed as characters: 𝛼 ≤ 𝛽.

Each row shows the character sym.<name> gave, its code point and the LaTeX command for the same symbol: RR is ℝ, U+211D, which LaTeX writes \mathbb{R}, and dot.op is ⋅, U+22C5, LaTeX’s \cdot. When all you have is the symbol itself, copied from a PDF or a web page, its code point is the key to both names.

You can also type a symbol as itself. Typst’s symbol reference says you can always enter Unicode symbols directly into your text and formulas. LaTeX depends on the engine: pdfLaTeX stopped at $α ≤ β$ with Unicode character α (U+03B1) not set up for use with LaTeX, while LuaLaTeX with unicode-math set it, and its text read 𝛼 ≤ 𝛽.

LuaLaTeX tags every formula with MathML

A tagged PDFtagged PDF: A PDF that also stores its structure, such as headings, paragraphs and reading order, so screen readers and text extraction can follow it. Typst writes tagged PDF by default. More in “LaTeX and Typst: what they are and when to use each” stores a structure tree beside the page, and for a formula the most useful thing it can hold is MathMLMathML: The W3C's markup language for mathematics, which records a formula's structure, such as which part is a fraction or a power, so that browsers can lay it out and assistive technology can read it., the W3C’s markup for the structure of mathematics: which part is a fraction, which is a power. LaTeX’s tagging code is switched on with \DocumentMetadata, before \documentclass. The LaTeX Project’s usage instructions call LuaLaTeX the preferred engine and say it includes a basic TeX to MathML converter, and that with LuaLaTeX and unicode-math the mathematics is tagged with an associated fileassociated file: A file embedded in a PDF and attached to part of its structure. LaTeX's tagging code attaches the MathML and the TeX source of a formula to the formula this way., an embedded stream of XML. The session builds the same document with LuaLaTeX twice and with pdfLaTeX twice, checks each with veraPDF, and counts the MathML files in each PDF:

% LuaLaTeX: tagged PDF/UA-2, with MathML written for every formula by the tagging code.
\DocumentMetadata{lang=en, pdfstandard=ua-2, tagging=on}
\documentclass{article}
\usepackage{unicode-math}
\title{Roots of a quadratic}
\author{A. Learner}
\begin{document}
\section{Roots}
The equation $ax^2 + bx + c = 0$ has the roots
\[
  x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}.
\]
\end{document}

% pdfLaTeX: the same tagged document, with amsmath instead of unicode-math.
\DocumentMetadata{lang=en, pdfstandard=ua-2, tagging=on}
\documentclass{article}
\usepackage{amsmath}
\title{Roots of a quadratic}
\author{A. Learner}
\begin{document}
\section{Roots}
The equation $ax^2 + bx + c = 0$ has the roots
\[
  x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}.
\]
\end{document}

from session import files, require, run

# The same tagged document built twice by LuaLaTeX with unicode-math, as the tagging code needs a first run to write
# the MathML of every formula, and twice by pdfLaTeX. veraPDF checks each PDF against PDF/UA-2 (2>/dev/null hides the
# warnings its Java runtime prints). qpdf rewrites each PDF uncompressed, so grep can count the MathML and the TeX
# source files attached to its formulas. Last, the MathML LuaLaTeX wrote for the inline formula. The size of a tagged
# LuaLaTeX PDF changes by a byte from one temporary folder to the next, so the session prints it as [size].
require("verapdf", "qpdf")
files("a11y/math-a11y.tex", "a11y/math-a11y-pdf.tex")
run("""
lualatex -interaction=nonstopmode -halt-on-error math-a11y.tex | grep -E "^WARNING|Output written"
lualatex -interaction=nonstopmode -halt-on-error math-a11y.tex | grep -E "^WARNING|Output written"
verapdf --flavour ua2 --format text math-a11y.pdf 2>/dev/null
qpdf --qdf --object-streams=disable math-a11y.pdf lua-qdf.pdf
grep -a -c "application#2fmathml+xml" lua-qdf.pdf
grep -a -c "application#2fx-tex" lua-qdf.pdf
pdflatex -interaction=nonstopmode -halt-on-error math-a11y-pdf.tex > /dev/null
pdflatex -interaction=nonstopmode -halt-on-error math-a11y-pdf.tex | grep -E "^WARNING|Output written"
verapdf --flavour ua2 --format text math-a11y-pdf.pdf 2>/dev/null
qpdf --qdf --object-streams=disable math-a11y-pdf.pdf pdf-qdf.pdf
!grep -a -c "application#2fmathml+xml" pdf-qdf.pdf
grep -a -c "application#2fx-tex" pdf-qdf.pdf
sed -n '/<math/,/<\\/math>/p' math-a11y-luamml-mathml.html | head -14
""", mask=[(r"\(1 page, \d+ bytes\)", "(1 page, [size])")])

$ lualatex -interaction=nonstopmode -halt-on-error math-a11y.tex | grep -E "^WARNING|Output written"
WARNING: mathml missing for hash 15B9E78F3A7CB11EA59B95C9553FB928
WARNING: mathml missing for hash 820A61339C34FF574758C4EB3BA0B09F
Output written on math-a11y.pdf (1 page, [size]).
$ lualatex -interaction=nonstopmode -halt-on-error math-a11y.tex | grep -E "^WARNING|Output written"
Output written on math-a11y.pdf (1 page, [size]).
$ verapdf --flavour ua2 --format text math-a11y.pdf 2>/dev/null
PASS ~/demo/math-a11y.pdf ua2
$ qpdf --qdf --object-streams=disable math-a11y.pdf lua-qdf.pdf
$ grep -a -c "application#2fmathml+xml" lua-qdf.pdf
2
$ grep -a -c "application#2fx-tex" lua-qdf.pdf
2
$ pdflatex -interaction=nonstopmode -halt-on-error math-a11y-pdf.tex > /dev/null
$ pdflatex -interaction=nonstopmode -halt-on-error math-a11y-pdf.tex | grep -E "^WARNING|Output written"
Output written on math-a11y-pdf.pdf (1 page, [size]).
$ verapdf --flavour ua2 --format text math-a11y-pdf.pdf 2>/dev/null
PASS ~/demo/math-a11y-pdf.pdf ua2
$ qpdf --qdf --object-streams=disable math-a11y-pdf.pdf pdf-qdf.pdf
$ grep -a -c "application#2fmathml+xml" pdf-qdf.pdf
0
[exit status 1]
$ grep -a -c "application#2fx-tex" pdf-qdf.pdf
2
$ sed -n '/<math/,/<\/math>/p' math-a11y-luamml-mathml.html | head -14
<math xmlns="http://www.w3.org/1998/Math/MathML">
 <mi>𝑎</mi>
 <msup>
 <mi>𝑥</mi>
 <mn>2</mn>
 </msup>
 <mo lspace="0.222em" rspace="0.222em">+</mo>
 <mi>𝑏</mi>
 <mi>𝑥</mi>
 <mo lspace="0.222em" rspace="0.222em">+</mo>
 <mi>𝑐</mi>
 <mo lspace="0.278em" rspace="0.278em">=</mo>
 <mn>0</mn>
</math>

The first LuaLaTeX run warned that MathML was missing for both formulas; the second run embedded it, and the PDF held 2 MathML files and 2 files with each formula’s TeX source. The MathML of the inline formula is at the end of the session: <msup><mi>𝑥</mi><mn>2</mn></msup> says that 2 is a power of x, which the copied text ax2 could not say. Step through the two runs:

pdfLaTeX’s build also passed PDF/UA-2, yet it held 0 MathML files: the instructions say that other engines need the MathML supplied in a separate file, which a LuaLaTeX run can write. veraPDF, which describes itself as a validator for all PDF/A and PDF/UA parts, checks the rules of the standard; it does not check that the maths makes sense to a listener.

Typst’s PDF/UA-1 export refuses an equation without alt text

Typst writes tagged PDF by default, and its accessibility guide says that PDF/UA-1 enforces alternative descriptions for images and mathematics and requires a document title. For maths, Typst’s equations take the description as their alt parameter, which the equation reference says should describe the full equation in natural language. The session exports the same document twice with --pdf-standard ua-1, first without any alternative textalternative text: A description in words that a PDF or web page gives instead of something a reader may not see, such as an image or an equation. For an equation it reads the formula aloud.:

#set document(title: [Roots of a quadratic])
#set text(lang: "en")
= Roots
The equation $a x^2 + b x + c = 0$ has the roots
$ x = (-b plus.minus sqrt(b^2 - 4 a c)) / (2 a). $

#set document(title: [Roots of a quadratic])
#set text(lang: "en")
= Roots
The equation #math.equation(
  alt: "a x squared plus b x plus c equals 0",
  $a x^2 + b x + c = 0$,
) has the roots
#math.equation(
  block: true,
  alt: "x equals minus b plus or minus the square root of b squared minus 4 a c, all over 2 a",
  $ x = (-b plus.minus sqrt(b^2 - 4 a c)) / (2 a). $,
)

from session import files, require, run

# Typst's PDF/UA-1 export of the same document, first without any alternative text, then with a description on both
# equations. veraPDF checks the second PDF against PDF/UA-1, and pdfinfo -struct-text shows the structure tree. Last,
# Typst's HTML export of the same file, which writes every equation as MathML.
require("verapdf")
files("a11y/missing-alt.typ", "a11y/math-a11y.typ")
run("""
!typst compile --pdf-standard ua-1 missing-alt.typ
typst compile --pdf-standard ua-1 math-a11y.typ
verapdf --flavour ua1 --format text math-a11y.pdf 2>/dev/null
pdfinfo -struct-text math-a11y.pdf | grep -a -E "Document|H1|P \\\\(|Formula"
typst compile --features html --format html math-a11y.typ
grep -o "<math[^>]*>" math-a11y.html
grep -o "<msqrt>.*</msqrt>" math-a11y.html
""")

$ typst compile --pdf-standard ua-1 missing-alt.typ
error: PDF/UA-1 error: missing alt text
  ┌─ missing-alt.typ:4:13
  │
4 │ The equation $a x^2 + b x + c = 0$ has the roots
  │              ^^^^^^^^^^^^^^^^^^^^^
  │
  = hint: make sure your images and equations have alt text

error: PDF/UA-1 error: missing alt text
  ┌─ missing-alt.typ:5:0
  │
5 │ $ x = (-b plus.minus sqrt(b^2 - 4 a c)) / (2 a). $
  │ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  │
  = hint: make sure your images and equations have alt text

[exit status 1]
$ typst compile --pdf-standard ua-1 math-a11y.typ
$ verapdf --flavour ua1 --format text math-a11y.pdf 2>/dev/null
PASS ~/demo/math-a11y.pdf ua1
$ pdfinfo -struct-text math-a11y.pdf | grep -a -E "Document|H1|P \\(|Formula"
Document
  H1 "Roots" (block)
  P (block)
    Formula ["a x squared plus b x plus c equals 0"]:
  Formula ["x equals minus b plus or minus the square root of b squared minus 4 a c, all over 2 a"]:
$ typst compile --features html --format html math-a11y.typ
warning: html export is under active development and incomplete
 = hint: its behaviour may change at any time
 = hint: do not rely on this feature for production use cases
 = hint: see https://github.com/typst/typst/issues/5512 for more information

$ grep -o "<math[^>]*>" math-a11y.html
<math>
<math display="block">
$ grep -o "<msqrt>.*</msqrt>" math-a11y.html
<msqrt><msup><mi>𝑏</mi><mn>2</mn></msup><mo>−</mo><mn>4</mn><mi>𝑎</mi><mi>𝑐</mi></msqrt>

Typst refused the first file with PDF/UA-1 error: missing alt text, once for each equation, the inline one included, and wrote no PDF. With math.equation(alt: …) around both, the export succeeded, veraPDF printed PASS for PDF/UA-1, and the structure tree held two Formula elements whose text is the description. The same file exported as HTML wrote both equations as MathML, <math> and <math display="block">, as the 0.15.0 changelog announced; the HTML export printed a warning that it is under active development. The guide says that MathML in PDF 2.0 is still to come, so a Typst PDF carries the description and not the structure.

Four routes, four results. Answer the questions about your own document:

Alt text reads the formula aloud

Typst’s guide asks you to describe a formula as if read out loud in natural language. A description is written for a listener who cannot see the layout, so it says what the layout shows: “x equals minus b plus or minus the square root of b squared minus 4 a c, all over 2 a”. The words “all over” do the work of the fraction bar, and “the square root of … squared” makes the order of the operations clear.

Practise: find equations without alt text, then check the descriptions

Two small tools for a document that must pass PDF/UA-1. The first finds every Typst equation that has no alt text yet, before an export refuses the file; the second flags descriptions that read the markup instead of the maths. Each step has sample tests that run in your browser:

def equations_without_alt(source):
    """Return (line number, equation) for every equation of the Typst source that has no alt text."""
    # Replace this comment: find the equations of each line and check the call around each one.
    return []

from alts import equations_without_alt

MISSING = """#set document(title: [Roots of a quadratic])
#set text(lang: "en")
= Roots
The equation $a x^2 + b x + c = 0$ has the roots
$ x = (-b plus.minus sqrt(b^2 - 4 a c)) / (2 a). $"""


def test_the_lesson_file_without_alt_text():
    """both equations of missing-alt.typ, the inline one included"""
    assert equations_without_alt(MISSING) == [
        (4, "$a x^2 + b x + c = 0$"),
        (5, "$ x = (-b plus.minus sqrt(b^2 - 4 a c)) / (2 a). $"),
    ]


def test_an_equation_with_alt_text():
    """an equation inside math.equation with alt: is described"""
    assert equations_without_alt('The value #math.equation(alt: "x squared", $x^2$) is short.') == []


def test_an_equation_after_the_call():
    """the call ends at its closing parenthesis"""
    line = '#math.equation(alt: "y", $y$) and $z$'
    assert equations_without_alt(line) == [(1, "$z$")]


def test_a_call_without_alt():
    """math.equation alone does not describe the equation"""
    assert equations_without_alt("#math.equation(block: true, $ f(x) $)") == [(1, "$ f(x) $")]


def test_escaped_dollars_are_text():
    """a price is not an equation"""
    assert equations_without_alt("It costs \\$5, and $x$ is the count.") == [(1, "$x$")]

def alt_problems(alt):
    """Return the problems of one equation description: "empty", "markup", "names-the-layout"."""
    # Replace this comment: check for an empty text, then for markup, then for words about the layout.
    return []

from altcheck import alt_problems


def test_a_good_description():
    """the lesson's description of the quadratic formula"""
    text = "x equals minus b plus or minus the square root of b squared minus 4 a c, all over 2 a"
    assert alt_problems(text) == []


def test_an_empty_description():
    """spaces only"""
    assert alt_problems("   ") == ["empty"]


def test_markup_instead_of_words():
    """the formula's source code"""
    assert alt_problems("x^2") == ["markup"]
    assert alt_problems("x = (-b plus.minus sqrt(b^2 - 4 a c)) / (2 a)") == ["markup"]


def test_words_about_the_picture():
    """image of, and a description that starts with Equation"""
    assert alt_problems("Image of an equation") == ["names-the-layout"]
    assert alt_problems("Equation for the area") == ["names-the-layout"]


def test_both_problems():
    """markup and layout words together, in order"""
    assert alt_problems("formula: \\frac{a}{b}") == ["markup", "names-the-layout"]

Last, take one question at a time on each idea of the lesson; missed ideas return first:

Interview questions

Warm-up (fresher to 2–5 years): why can’t any OpenType font be used to set maths?

Because setting maths needs more than letter shapes. An OpenType maths font also carries a table of layout values: how far to raise a superscript, how thick to draw a fraction bar, how a sum sign grows in a display and how brackets stretch. Typst’s maths reference says that only special OpenType maths fonts are suitable for typesetting maths, and in LaTeX the unicode-math package loads them with \setmathfont under LuaLaTeX or XeLaTeX. A text font such as Libertinus Serif has none of that, so its companion Libertinus Math is the font to choose for its formulas; in a recorded build, the same formula set in New Computer Modern Math, Latin Modern Math, STIX Two Math and Libertinus Math differed in weight and width but kept its limits and fractions in place in every one.

Two harder questions follow, about making a thesis’s maths accessible and about 300 equations without alt text. Decide your first step before you open each one:

Key takeaways

• An OpenType maths font carries the symbols and their layout rules; unicode-math loads one with \setmathfont under LuaLaTeX or XeLaTeX, Typst with a show-set rule, and its maths font should match the text font.
• Symbols have names in both systems: the Comprehensive LaTeX Symbol List and unimath-symbols.pdf for LaTeX, the symbol reference for Typst; Typst and LuaLaTeX with unicode-math also take the characters themselves.
• LuaLaTeX with unicode-math and \DocumentMetadata{…, tagging=on} attaches MathML to every formula after two runs; pdfLaTeX’s build passed PDF/UA-2 with no MathML, so check the file, not only the verdict.
• Typst’s PDF/UA-1 export refuses every equation without alt, inline ones included, and its HTML export writes equations as MathML.
• Alt text reads the formula aloud in words, with “all over” or “divided by” where the layout groups, never the source code and never “image of”.