Elamur Groupantslatex-ast
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
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 |
span_quotient | span_quotient | partial source derived model | span_quotient |
normalization | normalization | partial source derived model | normalization |
traversal_order | traversal_order | partial source derived model | traversal_order |
unknown_projection | unknown_projection | partial source derived model | unknown_projection |
Parts
Model text
descriptant
latex-ast
norm collapses exactly one atom; empty is Row([]). walk is preorder and preserves row/cell order; Scripts visits base, sub, sup, optional roots visit index before body. unknowns collects names and actual stored spans; has_unknown traverses all nodes.
Epoch2026-10-31: full source reviewed before edits; prospective models retained externally. No optimization.
approximant
Forward relation
norm collapses exactly one atom; empty is Row([]). walk is preorder and preserves row/cell order; Scripts visits base, sub, sup, optional roots visit index before body. unknowns collects names and actual stored spans; has_unknown traverses all nodes.
No useful approximate executable metric for exact categorical syntax; future caps1/2/5/10% only.
invariant
Domain, invariant and cost
norm collapses exactly one atom; empty is Row([]). walk is preorder and preserves row/cell order; Scripts visits base, sub, sup, optional roots visit index before body. unknowns collects names and actual stored spans; has_unknown traverses all nodes.
Public Node permits non-normal forms; no validation enforces singleton Row absence. Span u32 represents byte coordinates but equality deliberately ignores them.
walk/size/has_unknown O(N), O(D) recursion; unknowns adds name bytes and K outputs; usize size overflow not separately guarded.
composition
Composition
norm collapses exactly one atom; empty is Row([]). walk is preorder and preserves row/cell order; Scripts visits base, sub, sup, optional roots visit index before body. unknowns collects names and actual stored spans; has_unknown traverses all nodes.
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
Span equality cannot distinguish coordinates; traversal cannot silently omit Unknown arguments or script children.
reverse_reconstruction
A structural equality class admits arbitrary span assignments. norm inverse of atom n includes [n], and when n is Row(v), v subject to normalization; original grouping/positions cannot be uniquely inferred.
span_quotient
Eq(Span a,Span b)=true independently of start/end.
normalization
norm([])=Row([]), norm([a])=a, norm(v)=Row(v) when len differs from1.
traversal_order
Root precedes children; scripts base/sub/sup and env row-major.
unknown_projection
unknowns preserves traversal order and stored offsets; has_unknown agrees with nonempty unknowns for finite valid trees.
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.
This page in Markdown → https://md.groupants.elamur.ai/free/en/mova/latex/src/ast.rs.groupant/