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Make DimensionalMeasurement SI-coherent and add typed Measurement operators - #11
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…rators DimensionalMeasurement now stores its value in coherent SI units, scaled by each unit type's coherentScale, so products and quotients agree wherever Foundation's base unit is not SI: litres, degrees, bytes, parts per million and L/100km. The information storage scale is derived from Foundation's own bit unit, because the base unit is the byte on Darwin and the bit on Linux. Angle and information become pseudo-dimensions, so angles and data sizes never mix with plain ratios. Equality uses a relative tolerance, and infinite values compare exactly. Concrete Measurement<A> op Measurement<B> -> Measurement<C> operators are generated from the dimension table by the GenerateTypedAlgebra executable, so an unannotated product is typed. CI fails when the generated files are stale. The retroactive literal conformances on Measurement are removed: they make x / 2 ambiguous against the typed operators. The README documents the typed operators, SI coherence and the 3.0 behaviour changes.
On Linux, Foundation builds litersPer100Kilometers with a reciprocal converter, so converting a base-unit measurement to miles per gallon inverted the value. convert(to:) now applies the target unit's converter to the base value directly, which gives the same result on Darwin.
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Summary
DimensionalMeasurementcomputes in coherent SI units instead of Foundation's base units, so1 m × 1 m × 1 mis 1 m³, not 1 L.Measurementdirectly (60 generated operators); a dimensionless result is aDouble.DimensionalMeasurementequality is relative, and infinite values compare exactly.Measurementno longer conforms to the literal protocols, which madex / 2ambiguous against the typed operators.Breaking
This is a 3.0 change. The README's "Migrating to 3.0" section lists every behaviour change, including the new
DimensionalUnit.coherentScalerequirement.Testing
swift test