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Exact proposed 1.9-to-2.0 API diff
The reviewed proposal is an empty compiled API diff. The complete 1.9 public surface remains available in 2.0; version 1.9.3 changes how the surface is presented, not what programs compile or how calls behave. An empty diff is a deliberate compatibility decision, not missing analysis.
The normative machine-readable diff is api-diff-1.9-to-2.0.json. It is checked against the exact owner/kind/name/signature baseline in public-api-1.9.json.
Consequences by category
| Category | Exact proposed consequence |
|---|---|
| Source | None. No declaration is added, removed, renamed, hidden, or given a different signature/default. |
| Behaviour | None. No numerical rule, ownership/mutation/aliasing contract, exception, status, tolerance, RNG, callback, or thread-safety behavior changes. |
| Warnings | None. No deprecation or compiler warning is added or removed. |
| Packaging | None. All current source units—including pressure, velocity, and focused finance alias units—direct-source use, and the Lazarus package remain present. |
| Documentary defaults | The 13 common paths appear first; advanced stable declarations remain documented; all 21 exact aliases and compatibility rows receive explicit guidance; generic scaffolding is labelled implementation support. |
Why compatibility entries remain
IMatrix, TMatrixKit, and TMatrixKitSparse are not removed and receive no deprecation warning. New double-real code is directed to the named typed facades through explicit copying conversions. FinanceLib.Bonds and FinanceLib.NPV are retained because their focused aliases are semantically exact and useful; age or naming taste is not a removal reason.
The exact-alias review originally identified TPressureKit/EPressureError and TVelocityKit/EVelocityError as prospective canonicalization candidates. The 1.9.7 migration and package-boundary rehearsal retained all four: focused imports remain useful, exact, and dependency-neutral. Documentation may prefer the common facade for cross-fluid code, but no deprecation warning, removal, or package move is approved.
Separately routed capability
The common-program review identified ergonomic 2-D and 3-D vector rotation as useful. The 1.9.9 convergence gate closed the routing in the 1.10.0 capability manifest:
- 2-D
TVector2D.Rotate(const Angle: Double): TVector2Dis declared for 1.10.0 only, with a closed contract (radians, counter-clockwise positive, allocation-free value operation, source immutability,Perpendicularagreement at π/2, magnitude preservation tolerance, zero-vector, and non-finite behavior), a test plan, a documentation plan, and an empty compatibility impact. - 3-D rotation is explicitly deferred beyond 2.0 because it must choose among axis-angle, quaternion, and matrix semantics and settle orientation, units, normalization, and naming.
This document still proposes no 1.9.x declaration, and 1.9.x does not implement the 1.10.0 addition.
Mechanical closure
tools/check_api_decision.py fails if any declaration lacks one of the five classifications, any plain compiler alias lacks exactly one five-part review, any compatibility row lacks exactly one decision/note, any recommended selector lacks an output-checked common example, any common example names generic implementation support, any domain/unit or convention is unresolved, or any source/behaviour/warning/packaging consequence differs from the explicit empty lists above.