Elamur Groupantsmlab-display-format-choice
The groupant beside mlab/src/display.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 |
state_invariant | state_invariant | partial source derived model | state_invariant |
failure_precedence | failure_precedence | partial source derived model | failure_precedence |
representation_transport | representation_transport | partial source derived model | representation_transport |
resource_cost | resource_cost | partial source derived model | resource_cost |
Model text
descriptant
mlab-display-format-choice
Accumulate finite maxabs/minabs and all_int; all-int branch chooses integer unless digits>15, otherwise fixed versus exponent depends on rounded digit extrema.
Modeling epoch — 2026-10-31
Prospective source read preceded edits. Bounded synthetic checks and selected existing safe tests exercise actual code; paired debug/release results and compiled negative-control assertions are retained externally. Frozen scenario, corpus, external measurement, full-school and training effects are unexecuted. Partial lexical syntax supplies no macro-expanded or semantic proof.
approximant
Forward relation
Accumulate finite maxabs/minabs and all_int; all-int branch chooses integer unless digits>15, otherwise fixed versus exponent depends on rounded digit extrema.
Domain
Valid Rust value/storage invariants and available bounded resources; exact branch and effect observations only.
Executable approximant gap
No useful percentage-error surrogate is established for these categorical, textual or effectful observations. Supported future caps are 1%, 2%, 5%, 10%; no executable approximation or production substitution is claimed.
invariant
Invariants and costs
Nonfinite strings require width at least four in integer/fixed branches; exponent width expands for large exponents.
Failure ordering
No Result errors; exact zero excluded from minabs update, which can remain infinity.
Cost
O(number of real values) scans and bounded float formatting per extrema.
models
Typed models — mlab-display-format-choice
Source-derived partial relations; finite checks do not prove universality.
behavior_complement
Nonfinite elements alone exclude making all_int false; integer values with more than 15 decimal digits exclude integer format.
reverse_reconstruction
Same RealFmt admits many value collections with equal threshold category and width; extrema and order generally unrecoverable.
state_invariant
Nonfinite strings require width at least four in integer/fixed branches; exponent width expands for large exponents.
failure_precedence
No Result errors; exact zero excluded from minabs update, which can remain infinity.
representation_transport
Exponent threshold uses dmax>=prec or dmin<=-2, after round_sig; common decimal precision is max endpoint requirements.
resource_cost
O(number of real values) scans and bounded float formatting per extrema.
tests
Evidence and limitations
Parent source checks: display::tests::scalars_short, display::tests::matrix_rows. The fragment's actual statements lie in the recorded byte range; parent checks need not exercise every branch in this fragment. See ../tests.md for source-level control and limitations.
AST projection generated twice to fresh files and compared byte-for-byte. Runtime evidence is finite and does not establish every branch, allocation failure, backend implementation or effect path. No optimization or speed claim.
This page in Markdown → https://md.groupants.elamur.ai/free/en/mova/mlab/src/display.rs.groupant/format-choice.groupant/