blood.ts

function fork(a, b) {
    return (
        (Math.random() < 0.5 ? a[0] : a[1])
        + (Math.random() < 0.5 ? b[0] : b[1])
    )
}

function rand() {
    const a = [
        "ii",
        "Ai",
        "Bi",
        "AA",
        "BB",
        "AB",
        "AB",
        "AB",
        "AB",
        "AB",
        "AB",
        "AB",
        "AB",
        "AB",
        "AB",
        "AB",
        "AB",
        "AB",
    ]
    return a[Math.floor(Math.random() * a.length)]
}

function randN(n) {
    return Array(n).fill().map(rand)
}

function mix(n) {
    return Array.from({ length: Math.floor(n.length / 2) }, (_, i) =>
        fork(n[2 * i], n[2 * i + 1]),
    )
}

function shuffle(a) {
    const array = a.slice()
    let currentIndex = array.length

    // While there remain elements to shuffle...
    while (currentIndex != 0) {
        // Pick a remaining element...
        let randomIndex = Math.floor(Math.random() * currentIndex)
        currentIndex--

        // And swap it with the current element.
        ;[array[currentIndex], array[randomIndex]] = [
            array[randomIndex],
            array[currentIndex],
        ]
    }

    return array
}

function nextgen(a) {
    return mix(shuffle(a)).concat(mix(shuffle(a)))
}

function count(a) {
    const c = (x) => a.filter((y) => y == x).length
    return [
        c("Ai") + c("iA"),
        c("AA"),
        c("Bi") + c("iB"),
        c("BB"),
        c("ii"),
        c("AB") + c("BA"),
    ]
}

function go(n, gens) {
    let f = randN(n)
    const ret = []
    for (let i = 0; i < gens; i++) {
        const [a1, a2, b1, b2, o, ab] = count(f)
        ret.push(
            i + "\t" + [a1 + a2, b1 + b2, o, ab].map((x) => x / n).join("\t"),
        )
        f = nextgen(f)
    }
    return ret.join("\n")
}

go(1e4, 1e4)