---
title: "mlab-index — Mova code model"
description: "Mova code model of mlab/src/index.rs: components with their labels, obernants and the model text."
url: "https://groupants.elamur.ai/free/en/mova/mlab/src/index.rs.groupant/"
---
Elamur: [Mova](https://md.mova.elamur.ai/free/en/) · [Dictionary](https://md.dictionary.elamur.ai/free/en/) · [Research](https://md.research.elamur.ai/free/en/) · **Groupants**

This page as HTML: <https://groupants.elamur.ai/free/en/mova/mlab/src/index.rs.groupant/>

# 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

- **kind:** groupant
- **status:** partial source bound model
- **source:** [`mlab/src/index.rs`](https://github.com/ElamurAI/mova-free/blob/main/mlab/src/index.rs)
- **source SHA-256:** `dccd47c7d5a96caa…`
- **repository folder:** [`mlab/src/index.rs.groupant`](https://github.com/ElamurAI/mova-free/tree/main/mlab/src/index.rs.groupant)
- **repository commit:** `855da7bd4a7b`

> **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](#approximant) |
| **ast** | partial | `syntax.json` |
| **composition** | partial | [composition](#composition) |
| **cost** | symbolic source derived | [invariant](#invariant) |
| **descriptant** | present | [descriptant](#descriptant) |
| **invariant** | partial | [invariant](#invariant) |
| **tests** | executed bounded checks | [tests](#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](#behavior-complement) |
| `reverse_reconstruction` | reverse_reconstruction | partial source derived model | [reverse_reconstruction](#reverse-reconstruction) |
| `representation_transport` | representation_transport | partial source derived model | [representation_transport](#representation-transport) |
| `failure_precedence` | failure_precedence | partial source derived model | [failure_precedence](#failure-precedence) |
| `resource_domain` | resource_domain | partial source derived model | [resource_domain](#resource-domain) |
| `interaction_relation` | interaction_relation | partial source derived model | [interaction_relation](#interaction-relation) |

## Parts

- [mlab-index-assignment](https://md.groupants.elamur.ai/free/en/mova/mlab/src/index.rs.groupant/assignment.groupant/)
- [mlab-index-deletion](https://md.groupants.elamur.ai/free/en/mova/mlab/src/index.rs.groupant/deletion.groupant/)

## 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.