Fix decibel (dB) parsing of logarithmic units (#62)#75
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UCUM "dB" was parsed as deci+byte (decibyte): the prefix branch resolved atoms via pint before applying the UCUM mapping, and bare "B" is pint's byte. Logarithmic units also cannot be linearly prefixed in pint (decibel is a distinct unit from bel), so map the supported decibel forms (dB, dB[W], dB[V], ...) to pint's decibel-family units explicitly. Also correct the bel reference units, which used logfactor 10 (decibel) instead of the UCUM lg/2lg factors (1 for power, 2 for field levels), so bare B[W] is now a true bel-watt. Fixes #62
Bump pre-commit-hooks (v5->v6), ruff (v0.11->v0.15) and codespell (v2.4.1->v2.4.2). Ignore uv.lock as it is not tracked.
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Related: #76 (Clearer error message for invalid UCUM units). |
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Issue #62 had more layers than expected from the report.
dB→ decibyte /dB[W]→ decibyte·watt: InUcumToPintTransformer.simple_unit, the prefix branch resolved the bare atom through pint before applyingMAPPINGS_UCUM_TO_PINT. Pint reads bareBas byte, sod+byte= decibyte. TheB→belmapping lived only in an unreachable fallback. And even with the mapping,dbelcan't work — pint forbids linearly prefixing a logarithmic unit, because decibel is a distinct unit from bel, not a prefixed bel.dB[mW]parse error: Genuinely correct — UCUM defines onlyB[W]andB[kW]for power; there is no milliwatt bel.dBmhas no UCUM representation. (Locked in by a test; the cryptic message is a separate grammar concern.)bel_*defs usedlogfactor: 10, making bareB[W]return decibel values (1.259 W instead of the true bel-watt 10 W).2 lg(field/amplitude levels:B[V],B[mV],B[uV],B[10.nV],B[SPL]) vslg(power levels:B,B[W],B[kW,]). So field bels need logfactor 2 and their decibels logfactor 20; power bels logfactor 1 and decibels 10.Changed files:
pint_ucum_defs.txt- correctedbel_*logfactors (1 for power, 2 for field) so bareB[...]are true bels; addeddecibel_spl/volt/millivolt/microvolt/10nanovolt/kilowatt(logfactor 20/10).ucum_pint.py- addedMAPPINGS_UCUM_PREFIXED_TO_PINT(e.g.dB→decibel,dB[W]→decibelwatt) consulted in the prefix branch of both transformers.test_ucum_pint.py- new tests covering decibel atoms, true-bel values, str-transformer consistency, and the invaliddB[mW].Fixes #62