Elamur Groupantsmlab-table-dates
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 |
calendar_transport | calendar_transport | partial source derived model | calendar_transport |
clock_boundary | clock_boundary | partial source derived model | clock_boundary |
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-dates
Civil-day conversion maps Unix day0 to719529. datenum_ymd carries month and adds day offset; parse_iso validates calendar roundtrip but accepts unbounded parsed clock values. datestr rounds fractional day to seconds and carries midnight; nonfinite emits NaT.
Epoch 2026-10-31: isolated source-bound fragment over bytes [325,4747); includes no claim beyond this relation. Source hash 7af3a65aabe33226d39f741909fd08d74c3b3e43390417c64e617a10704ac26b.
approximant
dates: forward relation
Civil-day conversion maps Unix day0 to719529. datenum_ymd carries month and adds day offset; parse_iso validates calendar roundtrip but accepts unbounded parsed clock values. datestr rounds fractional day to seconds and carries midnight; nonfinite emits NaT.
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
dates: invariant and cost
days_from_civil/civil_from_days form inverse on valid supported calendar dates; ISO parser additionally requires4-digit year layout.
Time values are floating parsed, not range checked; timezone suffix unsupported; date range checked before calendar roundtrip.
Scope-specific cost: O(1) calendar arithmetic plus O(input bytes + format chars) parsing/formatting; no overflow certificate for extreme i64.
models
behavior_complement
Invalid February30 excludes Some date; hour24 is not excluded. Formatting is second-resolution and cannot preserve arbitrary fractional day bits.
reverse_reconstruction
For datestr with a time-bearing pattern, an output admits datenum inputs rounding to the shown second, including midnight carry. iso_date first tests exact integrality: date-only output admits integral inputs only; nonintegral inputs may round to midnight but retain the datetime pattern. Valid civil roundtrip is unique only within the nonoverflow calendar domain.
calendar_transport
days_from_civil/civil_from_days form inverse on valid supported calendar dates; ISO parser additionally requires4-digit year layout.
clock_boundary
Time values are floating parsed, not range checked; timezone suffix unsupported; date range checked before calendar roundtrip.
branch_relation
Civil-day conversion maps Unix day0 to719529. datenum_ymd carries month and adds day offset; parse_iso validates calendar roundtrip but accepts unbounded parsed clock values. datestr rounds fractional day to seconds and carries midnight; nonfinite emits NaT.
resource_cost
O(1) calendar arithmetic plus O(input bytes + format chars) parsing/formatting; no overflow certificate for extreme i64.
tests
Evidence boundary
See ../tests.md for the actual selected source test and mutant. These tests sample the file, not every fragment branch. Invalid February30 excludes Some date; hour24 is not excluded. Formatting is second-resolution and cannot preserve arbitrary fractional day bits. 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/dates.groupant/