history

Managed scientific and conversion constants

id: LK-20260713-managed-calculation-constants
date: 2026-07-13
sequence: 48
type: refactor
compatibility: compatible
component: `labkit.dta` | `2.0.0 -> 2.0.1`
component: `labkit.rhs` | `1.0.0 -> 1.0.1`
component: `labkit.biosignal` | `1.0.0 -> 1.0.1`
component: `labkit_ChronoOverlay_app` | `1.3.5 -> 1.3.6`
component: `labkit_CSC_app` | `1.3.9 -> 1.3.10`
component: `labkit_NerveResponseAnalysis_app` | `1.3.4 -> 1.3.5`
component: `labkit_ResponseReviewStats_app` | `1.3.4 -> 1.3.5`
scope: Managed scientific and conversion constants

Context

Scientific coefficients, device-format gains, unit conversions, and numeric tolerances were sometimes left as unexplained literals or repeated across callers, making origin and change impact difficult to audit.

Decision and rationale

Give each semantic calculation constant one named owner and a nearby source or purpose comment, while exempting ordinary indices and explicit UI geometry that do not encode scientific meaning.

Changes

• Named and documented Rec.601, sRGB/CIE, DTA/RHS gains, SI conversions, tolerances, and empirical policies across facades and apps.
• Centralized repeated CSC charge-density, CIC display-unit, and curvature tolerance contracts.
• Added repository-wide magic-number and rectangle-interaction guardrails.

User and data impact

Calculation results are preserved, but future changes now expose the constant's meaning and provenance instead of silently editing an unexplained literal.

Compatibility and migration

No user migration is required. Public function call contracts and output schemas are unchanged by this record.

Validation

MagicNumberGovernanceTest, rectangle governance, module compatibility tests, and affected app tests cover centralized ownership and preserved numeric behavior.

Evidence

Source comments use the Constant: marker and guardrail diagnostics name the unmanaged file and line. Commit 125338c0 introduced the calculation-constant checks and the corresponding source annotations.

Known limitations and follow-up

The scanner targets semantically suspicious precision and notation; review is still required for simple integers or short decimals whose meaning is hidden.