The typographic measure function m defined below satisfies m(a) + m(b) ≤ m(a+b), but does not always take equality.
In jargon, m is subadditive, but many contents do not meet the Carathéodory’s criterion and thus not Lebesgue measurable.
let m(a) = measure(a).width
Solution
let x = [一口]
let y = [一、]
let z = [一 ]
let w = h(0.3em, weak: true)
Full code
#set page(height: auto, width: auto, margin: 2em)
#set text(10pt, font: "Noto Serif CJK SC", fallback: false)
#let solution = (
x: [一口],
y: [一、],
z: [一 ],
w: h(0.3em, weak: true),
)
```typc
let m(a) = measure(a).width
let x = ??
let y = ??
let z = ??
let w = ??
```
#let twin(expr, irregular: false) = (
{
set raw(lang: "typc")
expr
},
box(
outset: 0.25em,
stroke: if irregular { aqua },
eval(expr.text, scope: (
m: a => context measure(a).width,
..solution,
)),
),
)
#set table.hline(stroke: 0.5pt)
#table(
columns: 2 * (1 + 4),
align: (start, end),
stroke: (x, y) => if x > 0 and calc.even(x) { (left: 0.5pt) },
table.cell(colspan: 2, {}),
..twin(`m(x)`),
..twin(`m(y)`),
..twin(`m(z)`),
..twin(`m(w)`),
table.hline(),
..twin(`m(x)`),
..twin(`m(x + x)`),
..twin(`m(x + y)`),
..twin(`m(x + z)`),
..twin(`m(x + w)`),
..twin(`m(y)`),
..twin(`m(y + x)`, irregular: true),
..twin(`m(y + y)`, irregular: true),
..twin(`m(y + z)`, irregular: true),
..twin(`m(y + w)`, irregular: true),
..twin(`m(z)`),
..twin(`m(z + x)`, irregular: true),
..twin(`m(z + y)`, irregular: true),
..twin(`m(z + z)`, irregular: true),
..twin(`m(z + w)`),
..twin(`m(w)`),
..twin(`m(w + x)`),
..twin(`m(w + y)`),
..twin(`m(w + z)`),
..twin(`m(w + w)`),
table.hline(),
[], [],
..twin(`m(x + w + x)`, irregular: true),
..twin(`m(y + w + y)`, irregular: true),
..twin(`m(z + w + z)`, irregular: true),
..twin(`m(w + w + w)`, irregular: true),
)
Background
It makes the auto hanging indents of multiline headings inaccurate.
Roughly speaking, the auto indent should be m(numbering + h(0.3em)), but typst uses m(numering) + 0.3em, which can be larger.
I found this mystery while I was developing Fix auto hanging-indent for `一、` heading numbering by YDX-2147483647 · Pull Request #7247 · typst/typst · GitHub.
An additional joke
(Once posted to the Discord discussions channel on 2025-07-30)
#let x = state("x", 5)
#let x-- = x.update(x => x - 1)
- #context x.get();
- #x--;
- #context x.get();
- #x--;
- #context x.get();
