---
title: "school-field-fold — Mova code model"
description: "Mova code model of world/src/knowledge.rs: components with their labels, obernants and the model text."
url: "https://groupants.elamur.ai/free/en/mova/world/src/knowledge.rs.groupant/format.groupant/field-fold.groupant/"
---
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# school-field-fold

The groupant beside world/src/knowledge.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:** [`world/src/knowledge.rs`](https://github.com/ElamurAI/mova-free/blob/main/world/src/knowledge.rs)
- **source SHA-256:** `0128bd416063db7a…`
- **covers:** Ordered lesson field fold and legacy admission (bytes 6629–7881)
- **part of:** [school-format](https://md.groupants.elamur.ai/free/en/mova/world/src/knowledge.rs.groupant/format.groupant/)
- **repository folder:** [`world/src/knowledge.rs.groupant/format.groupant/field-fold.groupant`](https://github.com/ElamurAI/mova-free/tree/main/world/src/knowledge.rs.groupant/format.groupant/field-fold.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** | source derived partial | [forward](#forward) |
| **ast** | partial | `../../syntax.json` |
| **cost** | prospective source cost | [cost](#cost) |
| **descriptant** | present | [epoch-memory](#epoch-memory) |
| **invariant** | source derived partial | [invariant](#invariant) |
| **tests** | bounded named actual code | [checks](#checks) |

## 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 |
|---|---|---|---|
| `school-field-fold-complement` | behavior_complement | source derived inner bound | [behavior-complement](#behavior-complement) |
| `school-field-fold-preimage` | reverse_reconstruction | partial relational specification | [reverse-reconstruction](#reverse-reconstruction) |
| `school-field-fold-overwrite` | last_writer_relation | source derived partial | [overwrite](#overwrite) |
| `school-field-fold-append-order` | ordered_fold | source derived partial | [append-order](#append-order) |
| `school-field-fold-failure-prefix` | first_error_relation | source derived partial | [failure-prefix](#failure-prefix) |
| `school-field-fold-admission-gap` | entry_contract | source derived partial | [admission-gap](#admission-gap) |

## Model text


Subject: `world/src/knowledge.rs` at manifest source SHA. Horizon: one terminating call or explicitly named load prefix on finite synthetic inputs, pinned dependencies and ordinary allocation/I/O. This is a source-derived partial model; finite tests do not establish universal correspondence.

### forward

Initialize Lesson with file; trim lines and ignore blanks/comments; split the first colon. Scalar assignments overwrite; explain/fact/question vectors append through their helpers. Unknown keys, missing colon, numeric or question failures stop immediately. parse then requires positive n and nonempty facts/exercises/tests; parse_fields alone does not.

### invariant

Successful fold preserves list encounter order and last scalar values; file argument survives unchanged. A successful field fold can still fail legacy parse admission.

### cost

O(B) outer line/field scan plus string copies and invoked citation/question costs. Memory is retained Lesson strings, with overwritten scalar storage released.

### behavior-complement

Type: behavior_complement. In text/file/result transitions, exclude successful parse_fields after unknown fields, missing colon or invalid usize fields; exclude final scalar values from an overwritten earlier assignment. For parse exclude success with missing required vectors. Error-prefix effects are local, not published partial Lessons.

### reverse-reconstruction

Type: reverse_reconstruction. For a returned Lesson L, candidates include ignored comments/whitespace, arbitrary earlier valid scalar assignments overridden later, and ordered list lines whose helper projections equal L's vectors. For errors retain every prefix satisfying earlier steps then the matching failing line; subsequent text is unobserved.

### overwrite

Type: last_writer_relation. For each scalar field the last successfully decoded assignment decides its final value; distinct scalar-key reorderings commute absent errors, repeated-key reorderings need not. Domain and fixed-source assumptions are those above; this is a source-derived constraint, checked only by the bounded named oracle where applicable.

### append-order

Type: ordered_fold. Explanation and fact vectors preserve encounter order independently; a layered fact appends two adjacent entries. Questions retain each field's own order. Domain and fixed-source assumptions are those above; this is a source-derived constraint, checked only by the bounded named oracle where applicable.

### failure-prefix

Type: first_error_relation. An unknown first field masks a later malformed lesson number; numeric parsing may fail before end-of-document admission. No continuation after failure. Domain and fixed-source assumptions are those above; this is a source-derived constraint, checked only by the bounded named oracle where applicable.

### admission-gap

Type: entry_contract. parse_fields admits empty or question-only structures; parse additionally requires n>0 and facts/exercises/tests. Retention parse_material instead requires n>0 and nonempty course. Domain and fixed-source assumptions are those above; this is a source-derived constraint, checked only by the bounded named oracle where applicable.

### parent-interaction

Question decoding, citation scanning and fact projection are ordered calls inside this fold; any helper failure prevents final admission. Retention calls parse_fields through its separate parse_material gate. Sibling normalization ranges overlap this calling model intentionally.

### checks

`knowledge::wave34_tests::field_fold_overwrites_scalars_appends_lists_and_fails_first` directly executes this helper or its containing load/reuse path with literal expected results. Full source and selected test body reviewed; no implementation-copy oracle. Exact names, profile repetitions and mutation receipts are recorded in the wave34 evidence summary. These are finite synthetic witnesses; unobserved cases and opaque dependencies remain gaps.

### epoch-memory

2026-10-31 wave34: prospective relations saved before test additions. Production bytes preserved. This new finer scope retains its parent's earlier models and history. Shared partial syntax is generated twice and compared; no semantic AST or solver claimed. No teacher, corpus, model loading, successful examination, training or lesson replay is credited as persistent knowledge.