ecclesia/dist/election/attribution/proportionalFactory.js

Framework for political and electoral simulations

import { divmod } from "@gouvernathor/python";
import { NumberCounter } from "@gouvernathor/python/collections";
import { addThresholdToSimpleAttribution } from "../attribution/transform";
import { proportionalFromDivisorFunction, proportionalFromRankIndexFunction, rankIndexFunctionFromDivisorFunction, stationaryDivisorFunction } from "./proportionalBase";
const divisor1 = stationaryDivisorFunction(1);
export function jefferson({ nSeats }) {
    return proportionalFromDivisorFunction({
        nSeats,
        divisorFunction: divisor1,
    });
}
export const dHondt = jefferson;
const divisorPoint5 = k => 2 * k + 1; // int math is better than k + .5
export function webster({ nSeats }) {
    return proportionalFromDivisorFunction({
        nSeats,
        divisorFunction: divisorPoint5,
    });
}
export const sainteLague = webster;
export function hamilton({ nSeats }) {
    const attrib = (votes, _rest = {}) => {
        const seats = NumberCounter.fromEntries();
        const remainders = new Map();
        const sumVotes = votes.total;
        for (const [party, scores] of votes) {
            const [i, r] = divmod(scores * nSeats, sumVotes);
            seats.set(party, i);
            remainders.set(party, r);
        }
        seats.add([...remainders.keys()]
            .sort((a, b) => remainders.get(b) - remainders.get(a))
            .slice(0, nSeats - seats.total));
        return seats;
    };
    attrib.nSeats = nSeats;
    return attrib;
}
export const hareLargestRemainders = hamilton;
const huntingtonHillBaseRankIndexFunction = rankIndexFunctionFromDivisorFunction(k => Math.sqrt(k * (k + 1)));
const huntingtonHillRankIndexFunction = (t, a) => {
    if (a <= 0) {
        return Infinity;
    }
    return huntingtonHillBaseRankIndexFunction(t, a);
};
export function huntingtonHill({ nSeats, threshold, contingency = null }) {
    const attrib = addThresholdToSimpleAttribution({
        threshold,
        contingency,
        attribution: proportionalFromRankIndexFunction({
            nSeats,
            rankIndexFunction: huntingtonHillRankIndexFunction,
        }),
    });
    attrib.nSeats = nSeats;
    return attrib;
}
/**
 * Creates a highest-averages proportional attribution method.
 *
 * The exact method used is an implementation detail and may change between versions.
 */
export const highestAverages = webster;
/**
 * Creates a largest-remainders proportional attribution method.
 *
 * Implementation detail: the quota used is the Hare/Hamilton quota.
 */
export const largestRemainders = hamilton;
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