Elamur Groupantsmlab-interp-index-assignment
The groupant beside mlab/src/interp.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 | approximant |
| ast | partial | ../syntax.json |
| cost | symbolic source derived | invariant |
| descriptant | present | descriptant |
| invariant | partial | invariant |
| tests | executed 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 |
rhs_precedence | rhs_precedence | partial source derived model | rhs_precedence |
missing_target | missing_target | partial source derived model | missing_target |
end_context | end_context | partial source derived model | end_context |
column_coordinates | column_coordinates | partial source derived model | column_coordinates |
Model text
descriptant
mlab-interp-index-assignment
Assignment and index-context evaluation boundary.
Epoch 2026-10-31
Half-open source bytes [17664,19980); bound by parent source hash and scoped byte hash. Model covers only this fragment; parent composition explains joins.
approximant
Scoped forward relation
RHS Mat -> existing target Mat or undefined -> evaluate index args with pushed EndCtx -> index::assign -> store.
Domain and gap
Source-generated states within resource limits. Categorical relation has no executable percent surrogate.
invariant
Scoped invariant
A function-handle RHS is rejected before an invalid index is evaluated.
Cost
Index expression evaluation plus index::assign costs and target growth/copy. EndCtx stack adds one entry per active index evaluation; dimensions use unchecked products.
models
Scoped typed relations
behavior_complement
Nonmatrix RHS excludes target/index evaluation; failed undefined-target assignment excludes inserting that target. End-context evaluation must not retain its temporary stack entry after a returned error.
reverse_reconstruction
Successful target matrix admits initial empty or existing matrices and many index/value histories; error text constrains first rejected stage only.
rhs_precedence
A function-handle RHS is rejected before an invalid index is evaluated.
missing_target
Undefined target uses dimensions 0,0 and is inserted only after successful assignment.
end_context
Each index evaluation pushes then pops its dimension context before propagating its Result.
column_coordinates
Indices delegate to index module, not direct Rust offsets.
tests
Evidence scope
Parent selected tests: wave30_parse_runtime_and_output_state, wave30_bounded_state_and_fallback, parse_error_runs_nothing. This fragment shares parent syntax and finite checks; no separate test count or complete fragment coverage claim. Assertion-control association and unexecuted paths are in parent tests.md and source-test-map.json.
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