Elamur Groupantsmlab-ops-finite-range
The groupant beside mlab/src/ops.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 |
representation_transport | representation_transport | partial source derived model | representation_transport |
failure_precedence | failure_precedence | partial source derived model | failure_precedence |
resource_domain | resource_domain | partial source derived model | resource_domain |
interaction_relation | interaction_relation | partial source derived model | interaction_relation |
Model text
descriptant
Finite range count and endpoint
Zero step, any NaN input, or wrong sign direction yields n=0; zero endpoints are valid. Otherwise span=(b-a)/s; n=floor(span+3eps*max(abs(span),1))+1; last=a+(n-1)s snaps to b if close. at(k) uses start for first half and last for second half.
Modeling epoch 2026-10-31
Prospective source reading precedes test additions. Retained observations: VM can use RangeSpec lazily while core colon/materialized expressions allocate Vec. Char class preserved only both endpoints char and implicit step.
This is partial source-derived modeling, not proof, full semantic coverage, or a performance result. Public malformed representations, unbounded allocations and exhaustive numerical edge cases remain outside the checked fixtures.
approximant
Finite range count and endpoint forward relation
Zero step, any NaN input, or wrong sign direction yields n=0; zero endpoints are valid. Otherwise span=(b-a)/s; n=floor(span+3eps*max(abs(span),1))+1; last=a+(n-1)s snaps to b if close. at(k) uses start for first half and last for second half.
Domain: Finite span safely below usize::MAX, allocatable n, representable arithmetic; no percentage accuracy promise.
No executable Rust surrogate is supplied: categorical decisions require exact observations; numerical kernels have no measured approximation metric here. Future supported caps are 1%, 2%, 5%, 10% only.
invariant
Invariant and cost
at requires k<n; last is exactly b when snap criterion holds, not universally. range uses first element of arguments; empty supplies NaN and default step is 1.
Cost: range_spec O(1), at O(1), range_values O(n) time/storage.
Failure ordering: range converts first a then b then optional s; NaN/zero/direction gate before span, endpoint snap after count.
models
behavior_complement
Bounded valid at excludes overshooting by naive cumulative addition; zero-step range excludes elements. Infinite span is not guaranteed to return Result/error: saturating cast plus addition can overflow.
reverse_reconstruction
Observed nonempty vector constrains endpoints/step only through rounded formulas; singleton vector permits many steps. Empty fiber includes zero step, NaN inputs and wrong-direction triples.
representation_transport
at requires k<n; last is exactly b when snap criterion holds, not universally. range uses first element of arguments; empty supplies NaN and default step is 1.
failure_precedence
range converts first a then b then optional s; NaN/zero/direction gate before span, endpoint snap after count.
resource_domain
Finite span safely below usize::MAX, allocatable n, representable arithmetic; no percentage accuracy promise.
interaction_relation
VM can use RangeSpec lazily while core colon/materialized expressions allocate Vec. Char class preserved only both endpoints char and implicit step.
tests
Bounded evidence
Selected actual-code Rust test: ops::wave30::arithmetic with cargo test --offline --locked -p mlab --lib. CPU synthetic fixtures only. Two debug and two release runs, sorted named outcomes, numeric statuses, compiled assertion controls and exact source restoration are retained externally under the wave30 expressions receipt directory. The source-to-test map distinguishes runtime semantics from AST representation checks. This fragment shares the parent test: only the exercised branches are observed; its whole prose is not runtime coverage. No corpus, GPU, live filesystem inspection, callbacks, RNG shuffle or wall-clock execution.
Syntax is generated twice from exact source and compared. Lexical projection has no expansion/type/name resolution. No strict Clippy claim; existing dependency/style findings are not re-run merely for repetition.
This page in Markdown → https://md.groupants.elamur.ai/free/en/mova/mlab/src/ops.rs.groupant/finite-range.groupant/