# Lambda Notation

> λambda notation — how symbols render, everywhere

- Skill: `abaj8494/lambda-notation` (Agent Skill)
- Install (CLI): `npx skillmds@latest add abaj8494/lambda-notation`
- Raw SKILL.md: https://api.skillmd.com/api/skills/abaj8494/lambda-notation/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: abaj8494 (https://skillmd.com/u/abaj8494)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/abaj8494/lambda-notation

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# λambda notation — how symbols render, everywhere

The concern this skill owns is **rendering**, not subject content: the
mechanical rules that make math, prose, and callouts render cleanly in the
LambdaMind panes, Obsidian, and terminals. Every quantitative field skill
loads this, so the discipline is written once and inherited — never copied
into a subject skill.

## Inline and display math

- **Inline `$…$`.** No space just inside the delimiters: `$x^2$`, never
  `$ x^2 $`. A dollar sign meant as **currency is escaped**: `\$150`, `\$1.20`
  — an unescaped `$…$` around prose renders the prose as broken math.
- **Display `$$…$$`.** A blank line **before and after** the block (the
  `$$` blank-line rule); a `$$` jammed against text on either side fails to
  render as a block.
- **No bare underscores in prose.** `a_i` outside math becomes italics soup —
  keep subscripts inside `$…$` (`$a_i$`), or write them out in words.
- **`<` inside math is a card/line-eating trap.** `\(p<N\)` can be parsed as
  an opening tag and swallow everything to the next `>`. Write `p < N` with a
  space, or `\lt`, when the render target is HTML-ish (Anki cards especially).

## Where each form is allowed

- **File output (session files, the worksheet, atoms, cards):** LaTeX that the
  vault renderer shows — `$…$`, `$$…$$`, `\(…\)`/`\[…\]` per SPEC schema 1.
  The session file is the source of truth and must read cleanly on its own.
- **Terminal / chat prose with no math renderer:** use **unicode** math
  (`K = Σ⁻¹`, `∑`, `√`, `≤`), not raw LaTeX — raw `$\Sigma^{-1}$` in a plain
  terminal is noise. On agents without a math renderer, restated MCQ options
  are compact unicode.
- Restate answers self-contained: `Correct: **(b)** $h = \Sigma^{-1}\mu$`,
  never a dangling letter.

## Callout hygiene

Every line of a callout — including the `[!type]` title — starts with `> `; a
bare `[!warning]` renders as literal text. Re-emit the whole callout with
prefixes intact when replacing a checkbox block with a verdict.

## Prose conventions (house style)

- **Acronyms expand on first use** in any session document: "graph neural
  network (GNN)" first, bare `GNN` after. Files are re-read cold.
- **No emoji, ever** — session files, DAG files, chat. Classical print:
  typographic glyphs only — ✓ ✗ → ⇒ · § ¶ † ☞ (the manicule ☞ is the
  "see slides/reading" pointer). Colour emoji are vetoed on sight.

## Figures and charts

Notation is text; figures are not. For any diagram, plot, or chart — including
the mermaid `xychart-beta` traps and the TikZ compile-verify loop — use the
**`lambda-draw`** skill. Do not restate its rules here.