Elamur Groupantstreeagree-rules-subtype-pick
The groupant beside tools/treeagree/src/rules.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
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 | model.md |
| ast | partial | ../syntax.json |
| composition | partial | Composition |
| cost | partial | invariant-and-cost |
| descriptant | present | descriptant |
| invariant | partial | invariant-and-cost |
| tests | bounded checks | 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 |
reverse_reconstruction | reverse_reconstruction | partial source derived model | reverse_reconstruction |
equal_base | equal_base | partial source derived model | equal_base |
different_base | different_base | partial source derived model | different_base |
idempotence | idempotence | partial source derived model | idempotence |
head_independence | head_independence | partial source derived model | head_independence |
Model text
descriptant
Descriptant
pick(haiku,agreed) returns haiku if base relations equal, otherwise agreed.
Epoch 2026-10-31
Prospective source reading identified conditional input alignment, information loss and failure order before tests. Existing production code is retained; added tests use actual helpers. Finite results update this source-bound model, not all parser/corpus semantics.
No executable percentage surrogate has a justified observation metric for these categorical/effectful APIs. Future profiles require metric, domain and real-reference evidence at caps 1/2/5/10%; no higher cap. Syntax is partial lexical Rust projection without macro expansion or semantic resolution.
approximant
Forward approximant
pick(haiku,agreed) returns haiku if base relations equal, otherwise agreed.
Composition
This fragment is the exact byte-scoped helper identified in the manifest; its relation is restricted to the operations above.
The containing source wires this scoped relation to its callers. Treeagree proposal→gate→commit and treebanks parse→match→collect→render are actual joins; parsecmp is an independent diagnostic path. The external group model distinguishes these tags.
catalog
Typed models for treeagree-rules-subtype-pick
Subject: source SHA-256 1f33a4afa995261fb36eb9c29a0ab8fd1b624501e49713acaad28ece769f8120; manifest supplies exact source/byte scope. Domain: admitted states in forward model, nonoverflow arithmetic and successful allocations. Observation: one terminating invocation, except explicitly described file trace. Source-derived partial relations; named finite tests constrain selected cases only. Each entry holds arguments and environment fixed except its stated intervention.
behavior_complement
Result cannot be a third relation distinct from both inputs.
Operator: inner exclusion on admitted domain. Evidence: source branch derivation plus tests.md; unexercised branches remain hypotheses. Oracle: evaluate the scoped actual helper on admissible fixtures and compare this observation. No universal proof.
reverse_reconstruction
Given result r, compatible pairs either have haiku=r with equal bases or agreed=r with different bases; generally nonunique.
Operator: compatible antecedent relation, retaining ambiguity. Evidence: source branch derivation plus tests.md; unexercised branches remain hypotheses. Oracle: evaluate the scoped actual helper on admissible fixtures and compare this observation. No universal proof.
equal_base
Same-base agreed subtype does not replace draft subtype; exact representation preservation is intentional.
Operator: specialized observation relation under the stated fixed inputs. Evidence: source branch derivation plus tests.md; unexercised branches remain hypotheses. Oracle: evaluate the scoped actual helper on admissible fixtures and compare this observation. No universal proof.
different_base
Across base classes result equals agreed exactly, with no retention of draft subtype.
Operator: specialized observation relation under the stated fixed inputs. Evidence: source branch derivation plus tests.md; unexercised branches remain hypotheses. Oracle: evaluate the scoped actual helper on admissible fixtures and compare this observation. No universal proof.
idempotence
pick(r,r)=r for every Rel; repeated same agreed value stabilizes after first selection.
Operator: specialized observation relation under the stated fixed inputs. Evidence: source branch derivation plus tests.md; unexercised branches remain hypotheses. Oracle: evaluate the scoped actual helper on admissible fixtures and compare this observation. No universal proof.
head_independence
No head argument exists; Root/head consistency must be checked by propose or shape, not this function.
Operator: specialized observation relation under the stated fixed inputs. Evidence: source branch derivation plus tests.md; unexercised branches remain hypotheses. Oracle: evaluate the scoped actual helper on admissible fixtures and compare this observation. No universal proof.
tests
Scoped evidence
Parent native slice and exact names are in ../tests.md.
pick fragment is source-derived; native rule tests exercise proposals but do not exhaust relation subtype pairs.
This fragment has no independent full-coverage claim. Its byte range and source hash bind the source-derived relation; parent test success is evidence only where that helper is actually reached.
invariant-and-cost
Invariant and cost
Constant enum base comparisons and copy; no allocation or I/O.
Result cannot be a third relation distinct from both inputs.
The complement and specialized catalog constrain preserved coordinates and effect boundaries. Empty/malformed domains are only guaranteed where explicitly admitted. No whole-program cost bound follows from a helper bound.
This page in Markdown → https://md.groupants.elamur.ai/free/en/mova/tools/treeagree/src/rules.rs.groupant/subtype-pick.groupant/