sw.js

// roll a single n-sided die
function d(n) {
    return Math.floor(Math.random() * n) + 1;
}

// roll an exploding n-sided die
function dx(n) {
    var v = d(n); return v === n ? v + dx(n) : v;
}

// roll an exploding n-sided die along with an exploding D6
function ddx(n) {
    return Math.max(dx(n), dx(6));
}

function attack(attacker, defender) {
    var wild = 0, fullDefense = 0;
    // roll to remove shaken
    if (ddx(defender.spirit) - defender.wounds >= 4) defender.shaken = false;
    // roll to attack
    var a = ddx(attacker.fighting) + wild - fullDefense;
    if (a >= defender.parry) {
        // deal damage and compute wounds
        var damage = dx(attacker.strength) + dx(8) + wild;
        if (a >= defender.parry + 4) damage += dx(6);
        var wounds = Math.floor((damage - defender.toughness) / 4);
        if (defender.shaken && wounds === 0) wounds = 1;
        if (wounds > 0) defender.shaken = true;
        // soak damage if possible
        if (wounds > 0 && defender.bennies > 0) {
            defender.bennies--;
            var soak = Math.floor((ddx(defender.constitution) - defender.wounds) / 4);
            if (soak > 0) wounds -= soak;
            if (wounds == 0) defender.shaken = false;
        }

        if (wounds > 0) {
            defender.wounds -= wounds;
        }

        return defender.wounds <= -4;
    }
    return false;
}

function killAlrik() {
    var alrik = {
        agility: 8,
        strength: 8,
        constitution: 6,
        spirit: 6,
        fighting: 8,
        parry: 6,
        toughness: 8,
        wounds: 0,
        shaken: false,
        bennies: 2
    };
    for (var turn = 1; ; turn++) {
        if (attack(alrik, alrik)) {
            return turn;
        }
    }
}

function sample(fn, count) {
    var samples = [], i;
    for (i = 0; i < 200; i++) {
        samples.push(0);
    }
    for (i = 0; i < count; i++) {
        samples[fn()]++;
    }
    return samples;
}

function variance(samples, count) {
    var m = 0, v = 0, i;
    for (i = 0; i < samples.length; i++) {
        m += i * samples[i];
    }
    m /= count;
    for (i = 0; i < samples.length; i++) {
        v += Math.pow(i - m, 2) * samples[i];
    }
    v /= count;
    return [m, Math.sqrt(v)];
}

function graph(samples, count) {
    var i, s, x, p, f = 400;
    for (i = 0; i < samples.length; i++) {
        if (samples[i] > 0) {
            p = Math.round(samples[i] / count * 1000);
            if (p > .1) {
                s = "" + i;
                while (s.length < 2) {
                    s = " " + s;
                }
                s += ": ";
                x = Math.round(samples[i] / count * f);
                do {
                    s += "-";
                } while (--x > 0);
                console.log(s + " " + p / 10 + "%");
            }
        }
    }
}

var count = 10000;
var samples = sample(killAlrik, count);
console.log(variance(samples, count));
graph(samples, count);