Elamur Groupantsworld-schooltools-editing-restore-selection
The groupant beside world/src/schooltools.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 source model | forward |
| ast | partial | ../../syntax.json |
| composition | partial source model | composition |
| cost | partial source model | cost |
| descriptant | partial source model | epoch-memory |
| invariant | partial source model | invariant |
| tests | partial source model | checks |
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 |
|---|---|---|---|
world-schooltools-editing-restore-selection-behavior-complement | behavior_complement | partial source model | behavior-complement |
world-schooltools-editing-restore-selection-reverse-reconstruction | reverse_reconstruction | partial source model | reverse-reconstruction |
world-schooltools-editing-restore-selection-preflight_order | failure_order | partial source model | preflight_order |
world-schooltools-editing-restore-selection-duplicate_accounting | observation_relation | partial source model | duplicate_accounting |
world-schooltools-editing-restore-selection-newline_cardinality | representation_relation | partial source model | newline_cardinality |
world-schooltools-editing-restore-selection-filesystem_boundary | effect_boundary | partial source model | filesystem_boundary |
Model text
Wave34, 2026-10-31. Source-bound helper model; no universal proof or approximation-error certificate. Historical parent epoch remains intact.
forward
Resolve snapshot copy by parent-basename/file-basename. Read saved then current lines split on newline. Refuse unequal line counts, then refuse any zero or oversized requested index before writing. Copy selected saved lines in list order, count only actual differences, write whole joined buffer, report changes.
invariant
On preflight refusal the current file is unchanged. Successful restoration preserves all unselected lines and exact saved selected bytes including CR. Duplicate selected indices can increase requested count but not changed count twice.
cost
O(saved bytes+current bytes+indices+output bytes), O(saved/current bytes) memory; filesystem latency/atomicity unmeasured.
composition
line_numbers normally sorts/deduplicates CLI indices, but public restore_lines admits duplicates. snapshot supplies copy naming. Count/index validation precedes the replacement loop and final fs::write; write failures may partially affect disk, outside preflight invariant.
behavior-complement
Exclude a preflight-refused call writing any prefix of valid requested lines; exclude indexing zero or above line count. Exclude changing an unselected line on successful I/O. No exclusion of partial writes on filesystem failure is claimed.
reverse-reconstruction
Given saved file, index list and successful final current file, compatible pre-files agree with final bytes outside selected lines and have equal split-line cardinality; selected earlier bytes are unconstrained. Changed count additionally constrains how many selected distinct lines differed.
preflight_order
Read saved before current; line-count mismatch precedes index validation; any invalid index anywhere in list prevents the whole restore. Valid-first/invalid-later is not a prefix commit.
duplicate_accounting
After the first restoration of x its buffer line equals saved[x]; a second x contributes zero to changed, while report denominator remains input-list length.
newline_cardinality
split('\n') retains trailing empty row: final newline affects cardinality and can make otherwise similar logical lines incompatible. CR is part of each restored row.
filesystem_boundary
Ordinary fs::write is not atomic or crash durable. Fixture success and preflight non-effects concern uniquely created temporary paths only; live lesson path resolution remains unexecuted.
checks
Exact world library selections: schooltools::wave34_models::restore_preflight_and_duplicate_selection. Current repeated debug/release outcomes and compiled controls are in the root sidecar wave34-evidence.md. Only these supplied-input tests are current evidence; older parent module-wide receipts are historical. Macro bodies remain opaque.
epoch-memory
Prospective model saved before edits. This epoch deepens one existing node rather than renaming it. Production implementation unchanged; tests add helper-boundary observations where stated. No live lessons, frozen suites, model loading, teacher or network. Read-only symbolic relations are broader than the finite native domain.
This page in Markdown → https://md.groupants.elamur.ai/free/en/mova/world/src/schooltools.rs.groupant/editing.groupant/restore-selection.groupant/