@smartput/distance

The place kind's one operation: kyiv to warsaw is a length, measured along the great circle between the two.

import { PlaceDistance } from "@smartput/distance";

defineKind({ /* … */ ops: [new PlaceDistance(COUNTRIES).op] });

A class over a bare OpSignature because the fallback table is the part that varies: a build handed a different gazetteer measures from different capitals, and the op has to close over the one its kind registered. .op is what defineKind takes; between(l, r) is the same measurement asked of two Values directly, and metresBetween(a, b) is the arithmetic with no Value involved.

No data. @smartput/country names this package, so it cannot name that one back — which is also the honest shape of the dependency, since the op wants a position per unit and nothing else a country row carries.

What it refuses

A sphere of radius 6,371,008.8 m, not the WGS84 ellipsoid: the two disagree by under 0.5%, and each endpoint is a capital standing in for a whole country. That reading is recorded on the signature as a great-circle assumption, because driving distance is what a person often means and no free dataset carries it.

A postal code borrows its country's coordinates until a provider positions it, and measuring from that borrowed point answered "0 kilometres" for every pair of codes in one country — SW1A 1AA to EH1 1YZ, London to Edinburgh, measured zero. So it throws UnpositionedPlaceError instead, naming the provider path. A wrong answer delivered confidently is worse than an error that names the remedy.

Full documentation: Places and distances.