---
title: "latex-ast-stage2 — Mova code model"
description: "Mova code model of latex/src/ast.rs: components with their labels, obernants and the model text."
url: "https://groupants.elamur.ai/free/en/mova/latex/src/ast.rs.groupant/stage2.groupant/"
---
Elamur: [Mova](https://md.mova.elamur.ai/free/en/) · [Dictionary](https://md.dictionary.elamur.ai/free/en/) · [Research](https://md.research.elamur.ai/free/en/) · **Groupants**

This page as HTML: <https://groupants.elamur.ai/free/en/mova/latex/src/ast.rs.groupant/stage2.groupant/>

# latex-ast-stage2

The groupant beside latex/src/ast.rs in the Mova repository: what the code computes, what it never does, how to go back from its outputs, its invariants, cost and checks.

## Facts

- **kind:** groupant_fragment
- **status:** partial source bound model
- **source:** [`latex/src/ast.rs`](https://github.com/ElamurAI/mova-free/blob/main/latex/src/ast.rs)
- **source SHA-256:** `88786b90964d7ee3…`
- **covers:** unknowns runs walk and emits (backslash+command,stored span) or (begin{name},stored span) for unknown environments. has_unknown ORs the same node predicates without short-circuiting walk. size counts each node visit, including root and empty Row. (bytes 5489–7960)
- **part of:** [latex-ast](https://md.groupants.elamur.ai/free/en/mova/latex/src/ast.rs.groupant/)
- **repository folder:** [`latex/src/ast.rs.groupant/stage2.groupant`](https://github.com/ElamurAI/mova-free/tree/main/latex/src/ast.rs.groupant/stage2.groupant)
- **repository commit:** `855da7bd4a7b`

> **Implementation material.** A Mova code model describes this code at one source revision: partial models, finite checks and their stated scope. It is not a reviewed general exposition, and its labels are shown as written, never raised.

## Components

| component | label | where |
|---|---|---|
| **approximant** | partial | [approximant](#approximant) |
| **ast** | partial | `../syntax.json` |
| **composition** | partial | [composition](#composition) |
| **descriptant** | present | [descriptant](#descriptant) |
| **invariant** | partial | [invariant](#invariant) |
| **tests** | executed bounded checks | [tests](#tests) |

## Obernants

The typed relations around the forward model: the behaviour complement (what the code never does), the reverse reconstruction (every input compatible with an output) and specialised views.

| id | type | label | where |
|---|---|---|---|
| `behavior_complement` | behavior_complement | partial source derived model | [behavior_complement](#behavior-complement) |
| `reverse_reconstruction` | reverse_reconstruction | partial source derived model | [reverse_reconstruction](#reverse-reconstruction) |
| `unknown_presence` | unknown_presence | partial source derived model | [unknown_presence](#unknown-presence) |
| `node_count` | node_count | partial source derived model | [node_count](#node-count) |

## Model text


### descriptant

#### latex-ast-stage2

unknowns runs walk and emits (backslash+command,stored span) or (begin{name},stored span) for unknown environments. has_unknown ORs the same node predicates without short-circuiting walk. size counts each node visit, including root and empty Row.

Epoch 2026-10-31: replaced stage topic lists with concrete transitions, exclusions and compatible antecedents. Four meaningful typed views replace the previous six-view bookkeeping catalog. Shared syntax and source byte bounds are unchanged.

### approximant

#### Scoped forward relation

unknowns runs walk and emits (backslash+command,stored span) or (begin{name},stored span) for unknown environments. has_unknown ORs the same node predicates without short-circuiting walk. size counts each node visit, including root and empty Row.

This is an exact source-derived partial model, not an executable approximate replacement.

### invariant

#### Scoped invariants

An unknown-looking string inside Text cannot itself appear in unknowns. has_unknown cannot be false when unknowns is nonempty for a finite tree. Span-insensitive Node equality cannot establish coordinate equality.

has_unknown(n) iff !unknowns(n).is_empty(), under terminating traversal. Names preserve the spelling stored in Unknown/EnvName; spans are copied rather than recomputed.

size(n)=1+sum(size(child)); empty Row contributes1. Replacing a known leaf by another preserves size; adding a Group increases size by1.

### composition

#### Scoped interaction

These observers use the previous traversal stage. Their output coordinates remain meaningful even though Span::eq returns true for arbitrary coordinates; the appended tests explicitly distinguish those observations.

The manifest binds this stage to the unchanged parent syntax projection and exact source byte range. Parent cost remains an upper accounting context; no independent whole-file invocation or execution count is assigned to this fragment.

### models

### behavior_complement

An unknown-looking string inside Text cannot itself appear in unknowns. has_unknown cannot be false when unknowns is nonempty for a finite tree. Span-insensitive Node equality cannot establish coordinate equality.

### reverse_reconstruction

unknowns=[] is compatible with every tree containing no Unknown node or unknown Env, including empty Row and large known trees. A listed unknown's name/span does not determine its children or surrounding known nodes. size=1 is compatible with any leaf and also empty Row.

### unknown_presence

has_unknown(n) iff !unknowns(n).is_empty(), under terminating traversal. Names preserve the spelling stored in Unknown/EnvName; spans are copied rather than recomputed.

### node_count

size(n)=1+sum(size(child)); empty Row contributes1. Replacing a known leaf by another preserves size; adding a Group increases size by1.

### tests

#### Evidence — 2026-10-31

ast::wave28_tests::normalization_and_span_quotient; ast::wave28_tests::traversal_preserves_script_and_unknown_order

Selected library filters ast:: lex:: macros:: parse:: print:: table:: and integration gate excluding document_extraction_with_preamble_macros and random_token_soup_never_panics_and_roundtrips. Direct rustc --test latex/build.rs exercises private helpers. All selected tests twice debug/release with identical sorted names. Four compiled mutants at build/AST/parser/printer boundaries fail assertions then exact restoration passes. These do not individually cover every source. Build-main failure effects, allocation failures and universal roundtrip are unproved. Strict Clippy reports existing lints. No corpus/live VMM/API/GPU/full-school/held-out tests.