ecclesia/dist/chunk-PFWVE4EX.js

Framework for political and electoral simulations

import {
  defaultMetric
} from "./chunk-UWP5NKUP.js";

// src/election/attribution/proportionalBase.ts
import { Counter } from "@gouvernathor/python/collections";
function proportionalFromRankIndexFunction({ nSeats, rankIndexFunction }) {
  const attrib = (votes, rest = {}) => {
    const allVotes = votes.total;
    const fractions = new Map([...votes.entries()].map(([party, v]) => [party, v / allVotes]));
    const rankIndexValues = new Map([...fractions.entries()].map(([party, f]) => [party, rankIndexFunction(f, 0)]));
    const parties = [...votes.keys()].sort((a, b) => rankIndexValues.get(a) - rankIndexValues.get(b));
    const seats = new Counter();
    s: for (let sn = 0; sn < nSeats; sn++) {
      const winner = parties.pop();
      seats.increment(winner);
      rankIndexValues.set(winner, rankIndexFunction(fractions.get(winner), seats.get(winner)));
      for (let pn = 0; pn < parties.length; pn++) {
        if (rankIndexValues.get(parties[pn]) >= rankIndexValues.get(winner)) {
          parties.splice(pn, 0, winner);
          continue s;
        }
      }
      parties.push(winner);
    }
    return seats;
  };
  attrib.nSeats = nSeats;
  return attrib;
}
function boundedRankIndexMethod({ minNSeats, maxNSeats, rankIndexFunction, metric = defaultMetric }) {
  const attrib = (votes, rest = {}) => {
    const allVotes = votes.total;
    const fractions = new Map([...votes.entries()].map(([party, v]) => [party, v / allVotes]));
    const rankIndexValues = new Map([...fractions.entries()].map(([party, f]) => [party, rankIndexFunction(f, 0)]));
    const parties = [...votes.keys()].sort((a, b) => rankIndexValues.get(a) - rankIndexValues.get(b));
    const seats = new Counter();
    let bestSeats = seats.pos;
    let bestSeatsMetric = Infinity;
    s: for (let sn = 1; sn <= maxNSeats; sn++) {
      const winner = parties.pop();
      seats.increment(winner);
      if (sn >= minNSeats) {
        const newMetric = metric({ votes, seats });
        if (newMetric < bestSeatsMetric) {
          bestSeats = seats.pos;
          bestSeatsMetric = newMetric;
        }
      }
      rankIndexValues.set(winner, rankIndexFunction(fractions.get(winner), seats.get(winner)));
      for (let pn = 0; pn < parties.length; pn++) {
        if (rankIndexValues.get(parties[pn]) >= rankIndexValues.get(winner)) {
          parties.splice(pn, 0, winner);
          continue s;
        }
      }
      parties.push(winner);
    }
    return bestSeats;
  };
  attrib.minNSeats = minNSeats;
  attrib.maxNSeats = maxNSeats;
  return attrib;
}
function stationaryDivisorFunction(r) {
  return (k) => k + r;
}
function rankIndexFunctionFromDivisorFunction(divisorFunction) {
  return (t, a) => t / divisorFunction(a);
}
function proportionalFromDivisorFunction({ nSeats, divisorFunction }) {
  return proportionalFromRankIndexFunction({
    nSeats,
    rankIndexFunction: rankIndexFunctionFromDivisorFunction(divisorFunction)
  });
}

export {
  proportionalFromRankIndexFunction,
  boundedRankIndexMethod,
  stationaryDivisorFunction,
  rankIndexFunctionFromDivisorFunction,
  proportionalFromDivisorFunction
};
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