---
title: "latex-lex-stage1 — Mova code model"
description: "Mova code model of latex/src/lex.rs: components with their labels, obernants and the model text."
url: "https://groupants.elamur.ai/free/en/mova/latex/src/lex.rs.groupant/stage1.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**

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# latex-lex-stage1

The groupant beside latex/src/lex.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/lex.rs`](https://github.com/ElamurAI/mova-free/blob/main/latex/src/lex.rs)
- **source SHA-256:** `65c9e2c47772827a…`
- **covers:** next pops stack; peek reads last and peek2 next-to-last. push_front(t1..tk) extends reversed tokens so subsequent next yields t1..tk then the old stream. group_tokens tracks brace depth, returning at depth-zero Close; End is restored and yields failure. opt_tokens requires initial [, ignores ] within braces, restores depth-zero Close/End on failure. (bytes 4763–9128)
- **part of:** [latex-lex](https://md.groupants.elamur.ai/free/en/mova/latex/src/lex.rs.groupant/)
- **repository folder:** [`latex/src/lex.rs.groupant/stage1.groupant`](https://github.com/ElamurAI/mova-free/tree/main/latex/src/lex.rs.groupant/stage1.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) |
| `boundary_preservation` | boundary_preservation | partial source derived model | [boundary_preservation](#boundary-preservation) |
| `optional_scope` | optional_scope | partial source derived model | [optional_scope](#optional-scope) |

## Model text


### descriptant

#### latex-lex-stage1

next pops stack; peek reads last and peek2 next-to-last. push_front(t1..tk) extends reversed tokens so subsequent next yields t1..tk then the old stream. group_tokens tracks brace depth, returning at depth-zero Close; End is restored and yields failure. opt_tokens requires initial [, ignores ] within braces, restores depth-zero Close/End on failure.

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

next pops stack; peek reads last and peek2 next-to-last. push_front(t1..tk) extends reversed tokens so subsequent next yields t1..tk then the old stream. group_tokens tracks brace depth, returning at depth-zero Close; End is restored and yields failure. opt_tokens requires initial [, ignores ] within braces, restores depth-zero Close/End on failure.

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

### invariant

#### Scoped invariants

Failed collectors do not restore already consumed body tokens. End cannot be consumed permanently by group_tokens or opt_tokens; arg_tokens similarly restores Close/End and returns no argument. truncate never grows the stream.

End and an unmatched outer Close bound optional scans; group scan preserves only End, while exhausting the stack returns None. These differing failure states matter to parser fallback.

For [{]}], the bracket inside braces is data. Only a depth-zero ] closes the option; leading spaces are consumed even when no option follows.

### composition

#### Scoped interaction

Parser markers and macro argument readers call these mutators. Stack residual length is used by unknown-argument fallback, so collector failure is a state transition rather than a pure predicate.

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

Failed collectors do not restore already consumed body tokens. End cannot be consumed permanently by group_tokens or opt_tokens; arg_tokens similarly restores Close/End and returns no argument. truncate never grows the stream.

### reverse_reconstruction

After successful group_tokens, output tokens plus remaining stream reconstruct the consumed interior and a closing brace, but not the caller-consumed opening token. After failure, lost consumed tokens are not recoverable from residual stack. push_front has unique undo only if the pushed prefix and its exact length are known.

### boundary_preservation

End and an unmatched outer Close bound optional scans; group scan preserves only End, while exhausting the stack returns None. These differing failure states matter to parser fallback.

### optional_scope

For [{]}], the bracket inside braces is data. Only a depth-zero ] closes the option; leading spaces are consumed even when no option follows.

### tests

#### Evidence — 2026-10-31

lex::tests::lexes_commands_and_spaces; lex::tests::positions_are_bytes; lex::tests::render_is_stable

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.