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

The groupant beside prag/src/feats.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:** [`prag/src/feats.rs`](https://github.com/ElamurAI/mova-free/blob/main/prag/src/feats.rs)
- **source SHA-256:** `2a1a0bd6e43dd16f…`
- **covers:** Index previous acts by source-qualified document ordinal, independently of paragraph and input order. (bytes 16029–16702)
- **part of:** [prag-feats](https://md.groupants.elamur.ai/free/en/mova/prag/src/feats.rs.groupant/)
- **repository folder:** [`prag/src/feats.rs.groupant/previous.groupant`](https://github.com/ElamurAI/mova-free/tree/main/prag/src/feats.rs.groupant/previous.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 source model | [forward](#forward) |
| **ast** | partial | `../syntax.json` |
| **composition** | partial source model | [composition](#composition) |
| **cost** | partial source model | [cost](#cost) |
| **descriptant** | partial source model | [epoch-memory](#epoch-memory) |
| **invariant** | partial source model | [invariant](#invariant) |
| **tests** | partial source model | [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 |
|---|---|---|---|
| `prag-feats-previous-behavior-complement` | behavior_complement | partial source model | [behavior-complement](#behavior-complement) |
| `prag-feats-previous-reverse-reconstruction` | reverse_reconstruction | partial source model | [reverse-reconstruction](#reverse-reconstruction) |
| `prag-feats-previous-coupling` | constraint_relation | partial source model | [coupling](#coupling) |
| `prag-feats-previous-observation-fiber` | information_loss | partial source model | [observation-fiber](#observation-fiber) |

## Model text


Index previous acts by source-qualified document ordinal, independently of paragraph and input order.

Source snapshot: 2a1a0bd6e43dd16f7284e993f30d0f4971c447c9e2080616033d19ac8693611f. All relations concern this snapshot on the stated admissible domain. Models are source-derived partial relations; finite fixtures are evidence, not general proofs. Complement is a conservative inner constraint model. Reverse reconstruction preserves all compatible antecedents conceptually; no enumerating solver is implemented.

### forward

Build map M[(src,doc,ord)]=last input index for non-Tatoeba ord>0. Output None for Tatoeba or ord<=1, otherwise lookup M[(src,doc,ord-1)]. This is an identity lookup, not previous vector position.

### behavior-complement

Universe: Items to optional index vectors. Excludes cross-source/doc links, Tatoeba links, ord<=1 links, and selecting an earlier duplicate over the final matching predecessor. An edge may point forward in vector order; that is not excluded.

### reverse-reconstruction

Given edges retain all source/doc/ordinal assignments satisfying predecessor equality and last-wins duplicate constraints. Paragraphs, texts, titles and keys are unconstrained by this observation. Missing links permit absent predecessor, initial ordinal or Tatoeba.

### invariant

Returned indices lie within input; paragraph differences do not reset predecessor acts; guarded subtraction avoids i64 underflow. Same key collisions are explicitly last-wins, not rejected.

### cost

Expected O(N) hash operations and O(N) map space; doc strings are borrowed, source is a small enum. No measured speedup or executable approximation error bound is claimed.

### coupling

eval train_rows/predict_seq consume indices while separately deciding available labels/predictions. This function does not guarantee the predecessor was predicted earlier in input order.

### observation-fiber

Overwriting duplicate keys loses earlier indices. Distinct text/paragraph assignments give identical edges. Adding source to key removes accidental cross-source context without changing same-source duplicate policy.

### composition

eval train_rows/predict_seq consume indices while separately deciding available labels/predictions. This function does not guarantee the predecessor was predicted earlier in input order. No child fragments; this is one scoped relation.

### checks

prev_source_identity_and_last_duplicate failed old code with Tale/Gum collision, then passes source isolation, duplicate, paragraph and minimum ordinal checks. See the file-level evidence.md for exact log hashes and repeated run outcomes.

### epoch-memory

2026-10-30 wave13: initial source-bound model. Prospective model preceded edits. Existing normalization and quote rules were retained; tests expose their information loss. Source identity witness justified qualifying predecessor keys by Src. Annotation is isolated behind a private closure used by the production row wrapper; fixtures do not call or certify tokenizer/parser. AST is a partial syntax projection, macro bodies opaque; semantic AST, live model/corpus and general proof remain absent.