Elamur Groupantslatex-lex
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 |
byte_coordinates | byte_coordinates | partial source derived model | byte_coordinates |
substream_boundary | substream_boundary | partial source derived model | substream_boundary |
stack_order | stack_order | partial source derived model | stack_order |
render_loss | render_loss | partial source derived model | render_loss |
Parts
Model text
descriptant
latex-lex
lex appends tokens, borrows command substrings and reports base+byte offset. ASCII command words eat following ASCII whitespace; comments consume until LF; spaces and tilde collapse. Stream reverses vectors, pushes front in reverse, and preserves End on failed substream scans. render serializes tokens with control-word separators.
Epoch2026-10-31: full source reviewed before edits; prospective models retained externally. No optimization.
approximant
Forward relation
lex appends tokens, borrows command substrings and reports base+byte offset. ASCII command words eat following ASCII whitespace; comments consume until LF; spaces and tilde collapse. Stream reverses vectors, pushes front in reverse, and preserves End on failed substream scans. render serializes tokens with control-word separators.
No useful approximate executable metric for exact categorical syntax; future caps1/2/5/10% only.
invariant
Domain, invariant and cost
lex appends tokens, borrows command substrings and reports base+byte offset. ASCII command words eat following ASCII whitespace; comments consume until LF; spaces and tilde collapse. Stream reverses vectors, pushes front in reverse, and preserves End on failed substream scans. render serializes tokens with control-word separators.
Empty appends nothing; existing trailing Space affects append coalescing. UTF-8 input valid; base+byte offset must fit u32 for nonwrapping semantics.
O(B+T) lex/storage, push O(k), group scanning O(k), render O(output); u32 addition overflow and oversized input cast excluded by representable-offset domain.
composition
Composition
lex appends tokens, borrows command substrings and reports base+byte offset. ASCII command words eat following ASCII whitespace; comments consume until LF; spaces and tilde collapse. Stream reverses vectors, pushes front in reverse, and preserves End on failed substream scans. render serializes tokens with control-word separators.
Build generates table enums consumed by parser dispatch and printers. Lexer tokens feed macros and parser; parser returns AST whose equality ignores spans. Printers and gate compare that quotient, not original bytes. Shared parent syntax backs scoped stages; stages are byte-bound projections, not independent Rust modules.
models
behavior_complement
No parser errors are returned by lex; trailing backslash and malformed parameter syntax remain characters. End may not disappear through group_tokens failure.
reverse_reconstruction
Sources producing a token stream differ by comments and whitespace and command-word spacing. render removes End and maps CmdRaw to Cmd; exact reverse is a compatible-source set with those distinctions forgotten.
byte_coordinates
Greek alpha occupies2 bytes so subsequent token offsets differ from scalar columns.
substream_boundary
Group and optional collectors restore End, consume preceding tokens, and return failure.
stack_order
next(push_front([a,b],s))=a then b then old s.
render_loss
End absent and raw flag lost; separator required only control word before ASCII letter in render.
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/