---
title: "math-understand-chunk — Mova code model"
description: "Mova code model of math/src/understand.rs: components with their labels, obernants and the model text."
url: "https://groupants.elamur.ai/free/en/mova/math/src/understand.rs.groupant/chunk.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**

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# math-understand-chunk

The groupant beside math/src/understand.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_fragment
- **status:** partial source bound model
- **source:** [`math/src/understand.rs`](https://github.com/ElamurAI/mova-free/blob/main/math/src/understand.rs)
- **source SHA-256:** `5b3ac990c5e46e75…`
- **covers:** read_number builds Rat from digit forms or accumulates number words/multipliers; chunk tries signed/contextual number plus unit before bare unit before word. standins emits placeholder forms with each token mapped to its retained Item index. (bytes 4089–11541)
- **part of:** [math-understand](https://md.groupants.elamur.ai/free/en/mova/math/src/understand.rs.groupant/)
- **repository folder:** [`math/src/understand.rs.groupant/chunk.groupant`](https://github.com/ElamurAI/mova-free/tree/main/math/src/understand.rs.groupant/chunk.groupant)
- **repository commit:** `48f2e6f74146`

> **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` |
| **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) |
| `signed_context` | signed_context | partial source derived model | [signed_context](#signed-context) |
| `ambiguous_unit_context` | ambiguous_unit_context | partial source derived model | [ambiguous_unit_context](#ambiguous-unit-context) |

## Model text


### descriptant

#### math-understand-chunk

read_number builds Rat from digit forms or accumulates number words/multipliers; chunk tries signed/contextual number plus unit before bare unit before word. standins emits placeholder forms with each token mapped to its retained Item index.

Epoch 2026-10-31: replaced duplicate catalog sentences with concrete exclusions, compatible-antecedent examples and two distinct scoped behavioral views. Source and prior execution evidence are unchanged; this revision ran no tests.

### approximant

#### Scoped forward relation

read_number builds Rat from digit forms or accumulates number words/multipliers; chunk tries signed/contextual number plus unit before bare unit before word. standins emits placeholder forms with each token mapped to its retained Item index.

This source-derived relation is partial; no executable percentage surrogate or replacement is supplied.

### invariant

#### Scoped domain and invariants

Successful number/unit readers advance the consumed token index. Exact Rat/units live in Item, not parser standins. Failed Rat operations may surface as unrecognized lexical material.

##### Cost

Chunk advances monotonically, but read_number may scan multiword spans and Rat operations have arithmetic costs. standins formatting and output allocation scale with emitted forms.

### models

### behavior_complement

A recognized fractional word cannot absorb a unit in chunk's number branch. Successful standin emission cannot lose its owner index. Placeholder output does erase sign/unit details, so unique source reconstruction is excluded.

### reverse_reconstruction

Items -8 miles and +8 kilograms both emit ['8','units'] with owner[0,0], while retaining different Item values/units. Fractions1/3 and1/2 emit 'half'; placeholder-only preimage is set-valued.

### signed_context

A minus is folded into a number only when the previous emitted item is neither Qty nor Unit and the next token starts with an ASCII digit. Otherwise it remains a word/operator token.

### ambiguous_unit_context

Bare single-letter scales require to/into/in context; listed ambiguous UnitW abbreviations require a/per/each/every unless after_num=true. Same spelling thus has context-dependent chunk role.

### tests

#### Scoped evidence

Word numbers, fractions, unit ambiguity, speed and negative quantity placeholder ownership.

Named actual source fixtures: understand::wave28::{chunk_units_and_placeholder_transport}.

Parent tests.md records commands and paired profiles. No additional coverage inferred from parent fixtures outside this byte range; source-scoped numeric/parse properties remain partial.