clat

Colin's LaTeX Tidy — somewhere between a clang and a splat.

clat is a configurable LaTeX source formatter with opinions. It cleans up untidy .tex files: merging stray \labels onto their headings, spacing display math, splitting one sentence per line, normalising units, and a dozen more transformations — each one you can dial up, dial down, or switch off.

pip install clat-tidy
clat main.tex

The installed command is clat. (The PyPI distribution is clat-tidy because clat was already taken; everything you type is still clat.)

clang, clunk, splat

Every rule has a weight (0–10; 0 disables). You set a single threshold. What happens to a given rule depends on the combination of its weight, the threshold, and whether the rule is auto-fixable:

Outcome	Condition	Meaning
clang	weight ≥ threshold and fixable	auto-fixed in place
clunk	weight ≥ threshold and not fixable	needs your attention
splat	0 < weight < threshold	advisory — take it or leave it
off	weight ≤ 0	disabled

Fixable splats are still fixed

A fixable rule that falls below the threshold still rewrites the text — it's just reported as a quiet splat rather than a loud clang. The threshold controls how much noise clat makes, not whether safe fixes happen. Set a rule's weight to 0 to disable it entirely.

Why "clat"?

Prosaically, clat is Colin's LaTeX Tool. But the name also has a bit of printer's noise in it.

In the "Aeolus" episode of Ulysses — "How a great daily organ is turned out" — Bloom moves through the newspaper office amid the machinery of print: clanking, rhythmic, three-four time; thump, thump, thump. My great-great-grandfather, a Dublin printer, is mentioned there too, though some editions mangle Caprani as Cuprani.

So clat is meant to sound a little like that composing-room racket: a small, opinionated machine for turning untidy copy into clean type.

How clat compares

The usual LaTeX formatting tools — latexindent, tex-fmt, prettier-plugin-latex — are excellent at indentation and line wrapping. They normalise whitespace, align tables, and keep columns tidy.

clat operates at a different layer. It doesn't touch indentation. Instead, it applies content-aware style rules that those tools don't cover:

What you need	Tool
Indentation, line wrapping, alignment	latexindent, tex-fmt
Style conventions and writing hygiene	clat

For example, clat can:

• Merge stray \labels onto their \section lines
• Split prose to one sentence per line
• Replace {\bf text} with \textbf{text}
• Configure inline and display math delimiter preferences separately
• Ensure ~ before \ref, \cite, and similar commands
• Replace ... with \dots
• Normalise number-unit spacing (100\,kN)
• Detect hardcoded references (Figure 3 instead of \cref{...})
• Add trailing punctuation to display equations
• Convert superscript ordinals (1\textsuperscript{st} → 1st)
• And more

None of these are available in latexindent, tex-fmt, or prettier-plugin-latex. clat is complementary — you can (and should) run both. A typical pipeline:

tex-fmt main.tex    # indentation, line wrapping
clat main.tex       # style rules

The weight/threshold system (clang/clunk/splat/off) also gives you granular control over which rules auto-fix, which flag for manual review, which are just advisory noise, and which are disabled — something the existing tools don't offer.

Where to next

• Installation

  Install from PyPI or set up a development checkout.

• Quick start

  Format your first file and read a clat report.

• Rules

  All 18 rules, what each does, and before/after examples.

• Configuration

  Tune weights and the threshold via .clat.toml.

• CLI reference

  Every command and flag.

• Python API

  Call clat from your own scripts.