Elamur Groupantsrt-mixed-diff-lcs
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
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 |
| cost | symbolic source derived | invariant |
| 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 |
score_bounds | score_bounds | partial source derived model | score_bounds |
tie_direction | tie_direction | partial source derived model | tie_direction |
form_only | form_only | partial source derived model | form_only |
quadratic_storage | quadratic_storage | partial source derived model | quadratic_storage |
Model text
descriptant
Descriptant
Prospective epoch
2026-10-31 source review predicted: Suffix DP uses equal-form diagonal+1 else max; traversal advances original on ties. Resource model: O(n*m) DP time and memory, plus form comparison bytes; reconstruction O(n+m). 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.
Narrow Form LCS alignment scope; finite checks do not cover all inputs. Parent effects and other functions are outside this fragment.
approximant
Forward relation
Suffix DP uses equal-form diagonal+1 else max; traversal advances original on ties.
Domain: Scope: Form LCS alignment. 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
Scope: Form LCS alignment. 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
O(n*m) DP time and memory, plus form comparison bytes; reconstruction O(n+m).
Limits
Narrow Form LCS alignment scope; finite checks do not cover all inputs. Parent effects and other functions are outside this fragment. 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.
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
Within this scoped helper relation, outputs violating the stated forward equation or its preserved fields are excluded under the domain premises; this is a partial source-derived inner exclusion, not a claim about untested panics. u32 score<=min(n,m) within admitted size.
reverse_reconstruction
Witness pairs do not recover mismatched tokens; repeated equal forms have other optimal alignments.
score_bounds
u32 score<=min(n,m) within admitted size
tie_direction
unequal forms with equal suffix scores advance i
form_only
lemma/tag/rel/space ignored by LCS
quadratic_storage
(n+1)*(m+1) u32 cells allocated before traversal
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.
Narrow Form LCS alignment scope; finite checks do not cover all inputs. Parent effects and other functions are outside this fragment.
This page in Markdown → https://md.groupants.elamur.ai/free/en/mova/tools/roundtrip/src/diff.rs.groupant/lcs.groupant/