61 lines
1.8 KiB
TypeScript
61 lines
1.8 KiB
TypeScript
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type Bid = { yesBid: number; noBid: number }
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// An entry has a yes/no for bid, weight, payout, return. Also a current probability
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export type Entry = {
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yesBid: number
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noBid: number
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yesWeight: number
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noWeight: number
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yesPayout: number
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noPayout: number
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yesReturn: number
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noReturn: number
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prob: number
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}
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export function makeEntries(bids: Bid[]): Entry[] {
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const entries: Entry[] = []
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let yesPot = 0
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let noPot = 0
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// First pass: calculate all the weights
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for (const { yesBid, noBid } of bids) {
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const yesWeight =
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noPot * (Math.log(yesBid + yesPot) - Math.log(yesPot)) || 0
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const noWeight = yesPot * (Math.log(noBid + noPot) - Math.log(noPot)) || 0
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// Note: Need to calculate weights BEFORE updating pot
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yesPot += yesBid
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noPot += noBid
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const prob = yesPot / (yesPot + noPot)
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entries.push({
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yesBid,
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noBid,
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yesWeight,
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noWeight,
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prob,
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// To be filled in below
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yesPayout: 0,
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noPayout: 0,
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yesReturn: 0,
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noReturn: 0,
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})
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}
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const YES_SEED = bids[0].yesBid
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const NO_SEED = bids[0].noBid
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const yesWeightsSum = entries.reduce((sum, entry) => sum + entry.yesWeight, 0)
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const noWeightsSum = entries.reduce((sum, entry) => sum + entry.noWeight, 0)
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// Second pass: calculate all the payouts
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for (const entry of entries) {
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const { yesBid, noBid, yesWeight, noWeight } = entry
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// Payout: You get your initial bid back, as well as your share of the
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// (noPot - seed) according to your yesWeight
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entry.yesPayout = yesBid + (yesWeight / yesWeightsSum) * (noPot - NO_SEED)
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entry.noPayout = noBid + (noWeight / noWeightsSum) * (yesPot - YES_SEED)
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entry.yesReturn = (entry.yesPayout - yesBid) / yesBid
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entry.noReturn = (entry.noPayout - noBid) / noBid
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}
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return entries
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}
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