Elamur Groupantsprag-infer-ancestry
The groupant beside prag/src/infer.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 source model | forward |
| ast | partial | ../../syntax.json |
| composition | partial source model | composition |
| cost | partial source model | cost |
| descriptant | partial source model | epoch-memory |
| invariant | partial source model | invariant |
| tests | bounded executed evidence | ../../model.md#evidence |
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-infer-ancestry-behavior-complement | behavior_complement | partial source model | behavior-complement |
prag-infer-ancestry-reverse-reconstruction | reverse_reconstruction | partial source model | reverse-reconstruction |
prag-infer-ancestry-broken-parent | failure_partition | partial source model | broken-parent |
Model text
forward
For fixed words W of length n and selected in-range top j, under(k) starts x=k. For at most n iterations: return true when x=j; otherwise follow a parent h only if 1<=h<=n, setting x=h-1; return false on missing/root/out-of-range parent. Exhaustion returns false. For functional in-range parent graphs, any first reach of top occurs within n distinct vertices.
behavior-complement
Universe: (W,k,j,b), with k,j supplied valid token coordinates and b Boolean. An inner bound of absent triples includes b=true when the path terminates at root or a dangling parent before top, and b=true for a cycle disjoint from top. Bounds are source-derived; malformed parent values are tolerated as absent evidence. The literal seven-token clause fixture includes a dangling branch and a two-node cycle and excludes both from content.
reverse-reconstruction
Given true, compatible graphs include k=j as well as every graph with a parent chain from k reaching j under the bound. Given false, compatible graphs include roots, dangling edges and disjoint cycles. The Boolean erases hop count and all off-path parents. Neither answer recovers a unique dependency tree. A graph with top itself in a cycle may still give true: the relation is reachability to top, not global well-formedness.
broken-parent
Hold a path prefix from k fixed. Outcomes partition into reaches-top, stops-at-root, stops-at-out-of-range, or exhausts-hop-bound. Root and broken-parent termination map to the same false observation, but have different repair hypotheses. A dangling unrelated branch should not abort the whole presupposition call; the old fixture did panic and the repaired fixture renders exactly she ran.
invariant
Every indexed current coordinate is checked through get; only a bounded nonzero parent is followed. At most n steps, so non-reaching cycles terminate. Parent coordinates are one-based; selected top and current x are zero-based.
composition
This predicate is private inside presuppositions and executes on its actual clause-filter path. Successful under alone does not emit a word: the caller also removes direct Mark children and preserves token order. Its true/false projection cannot determine complete rendered clause text without those caller constraints.
cost
O(n) per membership call and O(1) extra state. n membership calls per selected clause give O(n²); do not add this to the parent's cubic bound again.
epoch-memory
The compiled old source panicked while traversing a supplied usize::MAX parent on an unrelated token. Checked parent lookup now terminates false; valid ancestry and non-reaching cycle behavior are preserved. The source-bound fragment selects only the closure, while its executed witness calls the enclosing public API.
This page in Markdown → https://md.groupants.elamur.ai/free/en/mova/prag/src/infer.rs.groupant/presupposition.groupant/ancestry.groupant/