Elamur Groupantslatex-print
The groupant beside latex/src/print.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 |
token_separation | token_separation | partial source derived model | token_separation |
optional_scope | optional_scope | partial source derived model | optional_scope |
fault_support | fault_support | partial source derived model | fault_support |
text_loss | text_loss | partial source derived model | text_loss |
Parts
Model text
descriptant
latex-print
to_latex walks AST using command-word and digit separators; optional right brackets escape, unknown followed by brace gets relax, aligned leading bracket gets relax. Scripts print primes/sub/sup, trailing empty table row compensated. to_text projects style/group distinctions to Unicode with all-or-none sub/sup conversion; to_sexpr exposes selected structure and unknown start positions.
Epoch2026-10-31: full source reviewed before edits; prospective models retained externally. No optimization.
approximant
Forward relation
to_latex walks AST using command-word and digit separators; optional right brackets escape, unknown followed by brace gets relax, aligned leading bracket gets relax. Scripts print primes/sub/sup, trailing empty table row compensated. to_text projects style/group distinctions to Unicode with all-or-none sub/sup conversion; to_sexpr exposes selected structure and unknown start positions.
No useful approximate executable metric for exact categorical syntax; future caps1/2/5/10% only.
invariant
Domain, invariant and cost
to_latex walks AST using command-word and digit separators; optional right brackets escape, unknown followed by brace gets relax, aligned leading bracket gets relax. Scripts print primes/sub/sup, trailing empty table row compensated. to_text projects style/group distinctions to Unicode with all-or-none sub/sup conversion; to_sexpr exposes selected structure and unknown start positions.
Arbitrary publicly constructed ASTs need not round trip; empty string prints empty Row, numeric boundary spaces preserve separate Num nodes, prime count bounded by u8 representation.
LaTeX O(N+output) with recursive stack O(D); text creates subtree strings and can repeat copying across nested wrappers, conservative O(D*output+N). Allocation failure unmodeled.
composition
Composition
to_latex walks AST using command-word and digit separators; optional right brackets escape, unknown followed by brace gets relax, aligned leading bracket gets relax. Scripts print primes/sub/sup, trailing empty table row compensated. to_text projects style/group distinctions to Unicode with all-or-none sub/sup conversion; to_sexpr exposes selected structure and unknown start positions.
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
Normal printer cannot use fault substitutions; intentional SwapFrac/DropSup/DropLast change only applicable structures. Plain text is not an injective encoding of the AST.
reverse_reconstruction
Canonical string preimage includes ASTs differing only spans and potentially nonnormalized structures; normalized parser trees are the intended round-trip domain. Text preimage additionally varies styles, groups, presentation variants and column metadata.
token_separation
Control word before alphanumeric and adjacent numeric fragments get separating space.
optional_scope
Right bracket prints rbrack in optional context; explicit Group resets optional flag inside.
fault_support
SwapFrac affects fractions, DropSup scripts, DropLast rows len>=3; unaffected trees can remain green.
text_loss
Text trims ends, drops dollar markers/styles, font families may collapse; no inverse guarantee.
tests
Evidence — 2026-10-31
print::tests::canonical_latex; print::tests::plain_text; integration golden outputs and corrupted_printer_turns_gate_red
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/print.rs.groupant/