📐rt-mixed-diff

The groupant beside tools/roundtrip/src/diff.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

Components

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.

Parts

• rt-mixed-diff-lcs

Model text

descriptant

Descriptant

Prospective epoch

2026-10-31 source review predicted: Compare increments sents/tokens/chrF then exact text early-return. Otherwise form LCS with skip-original tie, adjacent aligned spacing, then greedy Order, Typography, Case, lemma Tense/Form, PronName and Lexical passes; leftovers classified missing/added. Resource model: LCS O(nm) time and memory; six greedy passes O(nm*string comparison cost); output examples capped by tally, context construction bounded scalar90 but scans full input. External prospective.md predates test additions and preserves APIs, effect order, hazards and interaction hypotheses.

Observed epoch

Bounded real helper checks in tests.md constrain these models; syntax is a partial lexical projection with no macro expansion, name resolution or proof. Production expressions unchanged; six inline test modules added. Compiled mutants are temporary and exactly restored. Existing malformed-input and nonfinite domains remain explicit, not silently repaired. Parent composes this scope with siblings without adding overlapping costs twice.

Finite synthetic helper evidence only; live corpora, parser/model loading, full orchestration and filesystem failure races excluded.

approximant

Forward relation

Compare increments sents/tokens/chrF then exact text early-return. Otherwise form LCS with skip-original tie, adjacent aligned spacing, then greedy Order, Typography, Case, lemma Tense/Form, PronName and Lexical passes; leftovers classified missing/added.

Domain: Valid token fields, lengths fit allocation and u32 LCS/counters. Exact strings can bypass inconsistent Tk fields; token coordinates are indices, cut truncates90 Unicode scalars.

invariant

Invariant and cost

Invariant

Valid token fields, lengths fit allocation and u32 LCS/counters. Exact strings can bypass inconsistent Tk fields; token coordinates are indices, cut truncates90 Unicode scalars.

Cost

LCS O(nm) time and memory; six greedy passes O(nm*string comparison cost); output examples capped by tally, context construction bounded scalar90 but scans full input.

Limits

Finite synthetic helper evidence only; live corpora, parser/model loading, full orchestration and filesystem failure races excluded. No percentage surrogate is implemented: categorical parsing/effect observations lack an admitted numerical error metric. Any future profile must define its metric/domain and use only1/2/5/10 percent caps.

composition

Local composition

Compare increments sents/tokens/chrF then exact text early-return. Otherwise form LCS with skip-original tie, adjacent aligned spacing, then greedy Order, Typography, Case, lemma Tense/Form, PronName and Lexical passes; leftovers classified missing/added.

Children select narrow source functions with their exact byte intervals. Remaining branches stay in the file model; fragments are not exhaustive partitions. Calls and state joins follow the forward relation, not folder order. Shared scans/helpers are counted once in whole-file costs. Complement of composition is not union of complements; reverse composition retains compatible intermediates and caller premises.

models

Typed source-bound relations

Subject: exact source SHA-256 in manifest. Domain and resource premises are in invariant.md. Each model is partial, source-derived, over a single helper invocation or the described finite trace. Complements are proposed inner exclusions under those premises; reverse relations retain all compatible antecedents, with no unique inverse claim. The oracle is the named checks in tests.md; unexecuted cases remain hypotheses. No numerical approximation certificate.

behavior_complement

Excluded: class counts are an invertible edit script or semantic equivalence judgment; exact text produces class divergences.

reverse_reconstruction

Divergence cells admit many alignments and original strings; LCS witness is deterministic but repeated forms have alternative optimal alignments.

alignment_tie

At equal unequal-form suffix scores, advance original i; greedy later pairing scans earliest unused j.

precedence

Typography before Case, lemma before PronName/Lexical; changing pass order changes classes.

spacing_scope

Only adjacent LCS neighbors in both sequences compare spacing; final-token spacing not independently counted.

scalar_preview

cut uses chars not byte slicing; previews retain90 scalars then ellipsis and lose remaining text.

tests

Checks and evidence

Named source/helper checks: diff::tests::classes_of_changes.

Wave32 on2026-10-31:10 distinct exact tests passed twice debug and twice release, with equal sorted named outcomes. This node claims only its listed subset; empty subset means source review only. Five actual source-behavior mutants compiled, failed assertions, restored exact bytes/hash, and passed focused green reruns. No assertion-only mutants; existing swapped-input controls are separate. Receipt bundle: $MOVA_DATA/runs/octopus-wave32-rt_mixed-2026-10-31 (native-commands.json, source-test-map.json, mutation-results.json, .status/.log). No live corpus, teacher, frozen assessment, download or production data used.

Finite synthetic helper evidence only; live corpora, parser/model loading, full orchestration and filesystem failure races excluded.

This page in Markdown → https://md.groupants.elamur.ai/free/en/mova/tools/roundtrip/src/diff.rs.groupant/