📐mlab-index

The groupant beside mlab/src/index.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

Components

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.

Parts

• mlab-index-assignment
• mlab-index-deletion

Model text

descriptant

One-based indexing and transactional bounded assignment

to_indices converts positive integral finite numeric x to usize(x)-1, or logical nonzero positions; colon spans extent. read validates upper bounds and gathers column-major; one vector index on vector source preserves source orientation, colon gives a column. assign validates shape then resizes with zero fill and writes ordered indices; duplicate destinations use the final RHS occurrence. 0x0 RHS selects deletion, deduplicating removal positions.

Modeling epoch 2026-10-31

Prospective source reading precedes test additions. Retained observations: interp turns Colon and End AST into IdxArg/extents. value supplies column-major Mat; reads narrow imaginary zeros; class merge preserves defined nonempty target Char, retains Logical only for logical/logical, otherwise Double; empty or undefined target adopts RHS class.

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

One-based indexing and transactional bounded assignment forward relation

to_indices converts positive integral finite numeric x to usize(x)-1, or logical nonzero positions; colon spans extent. read validates upper bounds and gathers column-major; one vector index on vector source preserves source orientation, colon gives a column. assign validates shape then resizes with zero fill and writes ordered indices; duplicate destinations use the final RHS occurrence. 0x0 RHS selects deletion, deduplicating removal positions.

Domain: Well-formed Mat, args lengths supported by each branch, finite indices representable below usize limit and bounded allocatable dimensions. Extra dimensions must be singleton; zero-argument deletion is outside modeled success domain.

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

All coordinates exposed to language are one-based; internal indices zero-based, layout j*rows+i. Ordinary Err from bounded validation precedes writes. Growth preserves old rectangle and zeros new cells. Empty deletion is only shape 0x0, not every zero-numel shape.

Cost: Read O(index elements+output); resize O(new area+old overlap); assign O(index+new area+RHS), deletion O(old area+index) with row/col completeness sorting O(k log k). No fallible allocation or checked dimension products.

Failure ordering: assign routes deletion before argument arity; extra-dimensional checks precede assign_2d. Numeric validity precedes read bound checks. Linear conformity precedes growth permission; 2D index conversion then RHS conformity precedes resize. read converts first two indices before row bounds.

composition

Parent composition

interp turns Colon and End AST into IdxArg/extents. value supplies column-major Mat; reads narrow imaginary zeros; class merge preserves defined nonempty target Char, retains Logical only for logical/logical, otherwise Double; empty or undefined target adopts RHS class.

Scoped fragments are projections over exact byte intervals in this source; they share one parent syntax projection. Uncovered declarations and embedded checks remain parent modeled. assign routes deletion before argument arity; extra-dimensional checks precede assign_2d. Numeric validity precedes read bound checks. Linear conformity precedes growth permission; 2D index conversion then RHS conformity precedes resize. read converts first two indices before row bounds.

The relation is source-derived and finite checks cannot establish complete correctness or a composition-wide numerical error bound.

models

behavior_complement

Within well-formed representable bounded domains, rejected conformity excludes changes to target, and duplicate index writes exclude first-write-wins. Reads exclude silently clipping out-of-bound positions. Logical masks are not validated against extent until read. No claim excludes panic on zero-argument delete, oversized casts, malformed buffers or allocation failure.

reverse_reconstruction

Gather output defines constraints m[idx[p]]=out[p], leaving unselected cells free; repeated index outputs must agree, and narrow may erase zero-im representation. Assignment preimage consists of prior matrices agreeing on unwritten retained cells; overwritten cells arbitrary. Deletion loses removed values and duplicate deletion multiplicity.

representation_transport

All coordinates exposed to language are one-based; internal indices zero-based, layout j*rows+i. Ordinary Err from bounded validation precedes writes. Growth preserves old rectangle and zeros new cells. Empty deletion is only shape 0x0, not every zero-numel shape.

failure_precedence

assign routes deletion before argument arity; extra-dimensional checks precede assign_2d. Numeric validity precedes read bound checks. Linear conformity precedes growth permission; 2D index conversion then RHS conformity precedes resize. read converts first two indices before row bounds.

resource_domain

Well-formed Mat, args lengths supported by each branch, finite indices representable below usize limit and bounded allocatable dimensions. Extra dimensions must be singleton; zero-argument deletion is outside modeled success domain.

interaction_relation

interp turns Colon and End AST into IdxArg/extents. value supplies column-major Mat; reads narrow imaginary zeros; class merge preserves defined nonempty target Char, retains Logical only for logical/logical, otherwise Double; empty or undefined target adopts RHS class.

tests

Source-specific bounded evidence

index::wave30::gather_update: vector orientation, shape-error rollback, zero-filled growth, duplicate writes/deletes, colon column, NaN index rejection, logical masks.

Seven named tests each passed twice debug and twice release on 2026-10-31, with actual named log lines sorted and identical across all four runs (28 selected successful executions). Each source has a compiled changed-assertion negative control; six runtime sources additionally have compiled production-body mutants that fail those unchanged tests. AST has representation evidence only. Every mutant is byte-restored and its positive test rerun. See evidence.json for this source's exact hash, mutation and exit statuses. External receipts retain full logs, command metadata, control records and prospective notes.

Unexecuted here: 2D growth/deletion and huge-index panic/resource cases unexecuted. No corpus, GPU, live filesystem, timer or callback run. No broad Clippy claim; dependency/style checks were not repeated. Only appended test blocks were rustfmt-formatted; original production bytes are unchanged.

This page in Markdown → https://md.groupants.elamur.ai/free/en/mova/mlab/src/index.rs.groupant/