Elamur Groupantsmlab-table-keys
The groupant beside mlab/src/table.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 | partial bounded parent evidence | 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 |
missing_relation | missing_relation | partial source derived model | missing_relation |
stable_ties | stable_ties | partial source derived model | stable_ties |
branch_relation | branch_relation | partial source derived model | branch_relation |
resource_cost | resource_cost | partial source derived model | resource_cost |
Model text
descriptant
mlab-table-keys
Ascending cmp orders NaN/None last and equal to themselves. Stable sorted_rows preserves tie indices; groups sorts by keys and restores appearance within each group. row_key returns None for any missing and canonicalizes signed zero.
Epoch 2026-10-31: isolated source-bound fragment over bytes [11897,15045); includes no claim beyond this relation. Source hash 7af3a65aabe33226d39f741909fd08d74c3b3e43390417c64e617a10704ac26b.
approximant
keys: forward relation
Ascending cmp orders NaN/None last and equal to themselves. Stable sorted_rows preserves tie indices; groups sorts by keys and restores appearance within each group. row_key returns None for any missing and canonicalizes signed zero.
Domain: Well-shaped public Table/Mat/StrArr, in-range zero-based internal indices, bounded i64 civil arithmetic. Malformed direct structs may panic.
Executable surrogate gap: no measured cheaper implementation with a useful scoped metric is supplied. Categorical/error/effect relations are exact obligations, not percent losses. Future numeric caps only1/2/5/10%.
invariant
keys: invariant and cost
NaNs group together but produce no hash key; +0 and -0 share numeric key0.
One-key numeric fast path adds original index as tie breaker; multi-key stable sort relies on sort stability.
Scope-specific cost: Sorting O(n log n * key-comparison cost); grouping stores O(n) indices; row_key O(k + copied text bytes).
models
behavior_complement
Missing grouping does not imply missing join equality; join keys exclude missing. Numeric/text keys remain distinct tagged atoms.
reverse_reconstruction
Sorted output admits any permutation of unequal-key source rows with corresponding index mapping; groups discard original inter-group order but retain member indices.
missing_relation
NaNs group together but produce no hash key; +0 and -0 share numeric key0.
stable_ties
One-key numeric fast path adds original index as tie breaker; multi-key stable sort relies on sort stability.
branch_relation
Ascending cmp orders NaN/None last and equal to themselves. Stable sorted_rows preserves tie indices; groups sorts by keys and restores appearance within each group. row_key returns None for any missing and canonicalizes signed zero.
resource_cost
Sorting O(n log n * key-comparison cost); grouping stores O(n) indices; row_key O(k + copied text bytes).
tests
Evidence boundary
See ../tests.md for the actual selected source test and mutant. These tests sample the file, not every fragment branch. Missing grouping does not imply missing join equality; join keys exclude missing. Numeric/text keys remain distinct tagged atoms. Other branches here are source-derived and unexecuted unless the parent test explicitly calls them.
This page in Markdown → https://md.groupants.elamur.ai/free/en/mova/mlab/src/table.rs.groupant/keys.groupant/