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

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# mlab-ast

The groupant beside mlab/src/ast.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/ast.rs`](https://github.com/ElamurAI/mova-free/blob/main/mlab/src/ast.rs)
- **source SHA-256:** `80c1551d46e07871…`
- **repository folder:** [`mlab/src/ast.rs.groupant`](https://github.com/ElamurAI/mova-free/tree/main/mlab/src/ast.rs.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` |
| **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) |

## Model text


### descriptant

#### Expression and statement representation

Expr is a tagged recursive sum: Num/Imag retain value and spelling, Str retains quote mode, Binary retains BinOp, Range retains optional step, Index retains argument order, AnonFn retains Rc body. Stmt stores one-based lexer line plus print/op metadata. Program partitions top-level statements and Rc function definitions.

##### Modeling epoch 2026-10-31

Prospective source reading precedes test additions. Retained observations: parser constructs these nodes; interp and vm consume them. Preserving End versus Ident(end), matrix rows and Pow versus EPow is required at that join; flattening any of them loses semantics.

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

#### Expression and statement representation forward relation

Expr is a tagged recursive sum: Num/Imag retain value and spelling, Str retains quote mode, Binary retains BinOp, Range retains optional step, Index retains argument order, AnonFn retains Rc body. Stmt stores one-based lexer line plus print/op metadata. Program partitions top-level statements and Rc function definitions.

Domain: Finite enum trees and ordered vectors; f64 payload permits NaN/Infinity. Public construction does not certify well-formed programs. No I/O or GPU effects.

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

Cloning Expr preserves payload and child order; Rc clones share anonymous bodies. Program::default has empty body/functions. Operator text uses != for Ne, which collapses source spellings ~= and != after lexing.

Cost: Clone traverses owned tree vectors/boxes and strings, O(owned nodes+text), but Rc body/function references clone O(1). text is O(1). No recursion depth cap.

Failure ordering: There is no fallible AST validation API. Allocation/recursive clone can fail externally; text exhaustively maps BinOp. Representation checks must not be reported as execution coverage.

### composition

#### Parent composition

parser constructs these nodes; interp and vm consume them. Preserving End versus Ident(end), matrix rows and Pow versus EPow is required at that join; flattening any of them loses semantics.

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. There is no fallible AST validation API. Allocation/recursive clone can fail externally; text exhaustively maps BinOp. Representation checks must not be reported as execution coverage.

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

### models

### behavior_complement

The representation relation excludes clone changing tags, ordered children, names or literal payload. BinOp::Pow and EPow are distinct even where scalar execution agrees. It does not exclude a hand-constructed invalid assignment or nonsensical line number; enums do not enforce grammar or evaluation.

### reverse_reconstruction

Given an Expr, compatible source strings are all texts parsed to its retained tags/payload; whitespace/comments are not uniquely recoverable. Clone's antecedent is any structurally equal tree; Rc anonymous-body cloning additionally retains pointer identity, not a fresh allocation. Runtime values cannot recover arbitrary syntax.

### representation_transport

Cloning Expr preserves payload and child order; Rc clones share anonymous bodies. Program::default has empty body/functions. Operator text uses != for Ne, which collapses source spellings ~= and != after lexing.

### failure_precedence

There is no fallible AST validation API. Allocation/recursive clone can fail externally; text exhaustively maps BinOp. Representation checks must not be reported as execution coverage.

### resource_domain

Finite enum trees and ordered vectors; f64 payload permits NaN/Infinity. Public construction does not certify well-formed programs. No I/O or GPU effects.

### interaction_relation

parser constructs these nodes; interp and vm consume them. Preserving End versus Ident(end), matrix rows and Pow versus EPow is required at that join; flattening any of them loses semantics.


### tests

#### Source-specific bounded evidence

`ast::wave30::representation`: Rc clone sharing, End/Colon child preservation, operator distinction, empty Program.

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: Representation only; AST is not an evaluator. 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.