Elamur Groupantslatex-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
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 |
| ast | partial | ../syntax.json |
| composition | partial | composition |
| descriptant | present | descriptant |
| invariant | partial | invariant |
| tests | executed bounded checks | 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 |
reverse_reconstruction | reverse_reconstruction | partial source derived model | reverse_reconstruction |
boundary_preservation | boundary_preservation | partial source derived model | boundary_preservation |
optional_scope | optional_scope | partial source derived model | 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.
This page in Markdown → https://md.groupants.elamur.ai/free/en/mova/latex/src/lex.rs.groupant/stage1.groupant/