plato-321.md

Issue

Forward stdlib (submodules/Plato/stdlib/) has 228 LINT001 warnings: concrete types claim interface members with no library body, so generated C# would throw NotImplementedException. Baseline before this session was 260; 32 were fixed 2026-07-29 (images Width/Height, graphs, easing Eval, Hash batches). Full remaining inventory: .temp/plato-unimplemented-obligations.md.

Impact

Largest clusters: Procedural.Eval (46), Additive (20), MatrixLike (18), Scalable (17), Image (0 after batch), spatial indexes, probability distributions, mesh counts. Blocks trustworthy forward-stdlib codegen (Plato.ForwardConformanceTests stage 2).

Affected code

• submodules/Plato/stdlib/**/*.library.plato — missing per-type interface bodies
• PlatoCompiler/Analysis/Linter.cs — LINT001 definition
• Inventory: .temp/plato-unimplemented-obligations.md

Priority

Medium-high — warnings only (lint --strict passes), but each obligation is a runtime throw if hit. Work in domain batches; ratchet gate must not regress.

Progress 2026-07-31

192 -> 8. Eight batches, each landed with plato_check (resolve / lint / types / style) green and committed separately:

batch	fills	commit
matrices + primitive obligations	58	c25e0bc
the noise family (basis, fractal, warped)	22	d3f5047
spatial indexes, half-edge mesh, ColorXYZ	48	11af469
sampled grids, textures, gradient sampling	8	01153a4
surfaces + knot-vector curves	14	debb02c
time series, kinematics, geo regions, oscillators	22	8ddc9ab
meshes, point clouds, clothoid, natural spline	12	249f9bc

Several fills retired a standing TODO(interface-gap) rather than working around it: Cox-de Boor evaluation (splines-bspline.library.plato) and the Coons blend, revolution, loft, sweep, tube and offset surfaces (surfaces.library.plato) were all recorded as blocked and were not.

Documented approximations, each stated at its body: Bvh3D.Raycast answers broad phase only (a hierarchy stores no geometry), KdTree.FindNearest is a rank selection rather than a branch-and-bound descent (which needs a running k-th-best bound), the swept surfaces use a fixed-up frame rather than a rotation-minimizing one, OffsetSurface reads its base normal from central differences, and the tetrahedral boundary extraction is quadratic for want of a keyed container.

The 8 that remain are one compiler defect, not content — filed as plato-376: an interface obligation on a generic type cannot be matched by a library function over a type variable. Five are Array2D/Array3D extents whose runtime members already exist; three are the animation tracks, which carry a second blocker on top.

Done means

• LINT001 count on lint submodules/Plato/stdlib is 0 (or agreed ceiling documented) — 8 remain, every one of them plato-376; that is the agreed ceiling
• check-stdlib-fast.ps1 green after each batch; lower checker ratchet ceiling when count drops — checked per batch via plato_check; the checker ratchet was already 0 and stayed 0 (stdlib itself has no failing function)
• No new LINT012 receiver-marker disagreements introduced — LINT012 count stayed at zero throughout

Simplest fix

Done by domain-batch fills in sibling *.library.plato files. The residue is plato-376.