Math

Typst’s native math notation works inside Mosaic slides. Incremental commands can then focus attention on one part of an equation at a time without changing its layout.

Incremental equations

The timing commands documented on the Reveal and replace page work inside math as well. Wrapping each term in m.steps.replace annotates one part of an equation at a time, and because the largest alternative sets the slot, the surrounding math never moves.

#import "@preview/mosaic:0.0.1" as m

#show: m.setup
#set text(size: 20pt)

// Enlarge the display equation so the annotations are easy to read.
#show math.equation.where(block: true): set text(size: 1.5em)

#let reward = rgb("#c2410c")
#let discount = rgb("#2563eb")
#let future = rgb("#15803d")

// A zero-width strut carrying a fixed descender depth. Adding it to each term
// gives every `underbrace` body the same depth, so all braces sit at the same
// level regardless of the term's own descenders.
#let dstrut = context { hide($j$) + h(-measure($j$).width) }

// Draw the annotated term, but constrain its measured footprint to the bare
// term's height. The brace and label then hang below the baseline instead of
// inflating the box, so `replace` keeps every term on the equation's baseline
// and nothing shifts when later annotations appear.
#let explained(color, term, label) = context {
  let braced = text(fill: color, $underbrace(#term #dstrut, #label)$)
  box(height: measure(text(fill: color, $#term$)).height, braced)
}

// The heading goes in the layout's header cell (anchored at the top) and the
// equation fills the body cell, which we align on the horizon to center it
// through the body cell's <mosaic-cell-body> label.
#show label("mosaic-cell-body"): set align(center + horizon)

#m.slide(layout: m.layouts.content(variant: "header-body"))[
  == Bellman optimality equation
][
  $
    V^star(s) = max_a
      #m.steps.replace(
        align: top + center,
        [$R(s, a)$],
        [#explained(reward, $R(s, a)$, [immediate reward])],
        [#explained(reward, $R(s, a)$, [immediate reward])],
        [#explained(reward, $R(s, a)$, [immediate reward])],
      )
      + #m.steps.replace(
        align: top + center,
        [$gamma$],
        [$gamma$],
        [#explained(discount, $gamma$, [discount factor])],
        [#explained(discount, $gamma$, [discount factor])],
      )
      #m.steps.replace(
        align: top + center,
        [$sum_(s') P(s' | s, a) V^star(s')$],
        [$sum_(s') P(s' | s, a) V^star(s')$],
        [$sum_(s') P(s' | s, a) V^star(s')$],
        [#explained(
          future,
          $sum_(s') P(s' | s, a) V^star(s')$,
          [expected optimal future value],
        )],
      )
  $
]

Annotate an equation one part at a time, first frame of 4

Open slideshow · 4 frames

LaTeX

The MiTeX package converts LaTeX math source into Typst content. Import mi for inline equations and mitex for display equations, useful when reusing existing equations or collaborating with LaTeX authors.

#import "@preview/mosaic:0.0.1" as m
#import "@preview/mitex:0.2.7": mi, mitex

#show: m.setup
#set text(size: 20pt)
#let slide = m.slide

#slide("content", variant: "body")[
  == LaTeX equations with MiTeX

  Write inline LaTeX such as #mi("\int_{-\infty}^{\infty} e^{-x^2}\,dx = \sqrt{\pi}") in ordinary text.

  #mitex(`
    \begin{aligned}
      \operatorname{Var}(X)
        &= \mathbb{E}\!\left[(X - \mathbb{E}[X])^2\right] \\
        &= \mathbb{E}\!\left[X^2 - 2X\,\mathbb{E}[X] + \mathbb{E}[X]^2\right] \\
        &= \mathbb{E}[X^2] - 2\,\mathbb{E}[X]^2 + \mathbb{E}[X]^2 \\
        &= \underbrace{\mathbb{E}[X^2]}_{\text{second moment}}
           - \big(\mathbb{E}[X]\big)^2 .
    \end{aligned}
  `)
]

Render LaTeX equations with MiTeX, first frame of 1

Open slideshow · 1 frame

Theorem

The ctheorems package provides numbered, referenceable theorem and proof environments. Define the environments once, install its thmrules show rule, and use them normally inside a Mosaic slide.

#import "@preview/mosaic:0.0.1" as m
#import "@preview/ctheorems:1.1.3": thmbox, thmproof, thmrules

#show: thmrules.with(qed-symbol: $square$)
#show: m.setup
#set text(size: 18pt)

#let theorem = thmbox(
  "theorem",
  "Theorem",
  fill: rgb("#eff6ff"),
)
#let proof = thmproof("proof", "Proof")

#let slide = m.slide

#slide("content", variant: "body")[
  == A theorem environment

  #theorem("Pythagoras")[
    For a right triangle with legs $a$, $b$ and hypotenuse $c$,
    $a^2 + b^2 = c^2$.
  ]

  #proof[
    Rearranging four congruent triangles inside a square shows that the
    uncovered area is both $c^2$ and $a^2 + b^2$.
  ]
]

Typeset a theorem and proof, first frame of 1

Open slideshow · 1 frame