function Stat() {
        this._base = 0;
        this._mods = {};
        this._current = undefined;

        if(typeof Stat.prototype.clearCache !== "function") {
            Stat.prototype.clearCache = function() {
                this._current = undefined;
            };
            Stat.prototype.addMod = function(id, mod) {
                id = String(id);
                if(Number.isFinite(mod)) {
                    mod = { add: mod };
                }
                if(typeof mod === "object") {
                    this._mods[id] = mod;
                    this.clearCache();
                }
            };
            Stat.prototype.removeMod = function(id) {
                delete this._mods[String(id)];
                this.clearCache();
            };
            Stat.prototype.clearMods = function() {
                this._mods = {};
                this.clearCache();
            };
            Object.defineProperty(Stat.prototype, "base", {
                get: function() {
                    return this._base;
                },
                set: function(newBase) {
                    newBase = Number(newBase);
                    /* alternative: newBase = setup.roll(newBase) for "3d6" as inputs */
                    if(!Number.isFinite(newBase)) {
                        newBase = 0;
                    }
                    if(this._base !== newBase) {
                        this._base = newBase;
                        this.clearCache();
                    }
                }
            });
            Object.defineProperty(Stat.prototype, "current", {
                get: function() {
                    if(this._current === undefined) {
                        /* gather multipliers */
                        var mult = Object.values(this._mods)
                            .map(function(m) { return Number.isFinite(m.mult) ? m.mult : 0; })
                            .reduce(function(sum, add) { return sum + add; }, 0);
                        var add = Object.values(this._mods)
                            .map(function(m) { return Number.isFinite(m.add) ? m.add : 0; })
                            .reduce(function(sum, add) { return sum + add; }, 0);
                        this._current = this.base * (mult + 1) + add;
                    }
                    return this._current;
                }
            });
            Stat.prototype.toString = function() {
                var mult = Object.values(this._mods)
                    .map(function(m) { return Number.isFinite(m.mult) ? m.mult : 0; })
                    .reduce(function(sum, add) { return sum + add; }, 0);
                var add = Object.values(this._mods)
                    .map(function(m) { return Number.isFinite(m.add) ? m.add : 0; })
                    .reduce(function(sum, add) { return sum + add; }, 0);
                return this.current.toFixed(2)
                    + " [" + this.base.toFixed(2)
                    + " x " + (mult + 1).toFixed(2)
                    + (add >= 0 ? " + " + add.toFixed(2) : " - " + (-add).toFixed(2))
                    + "]";
            };
            /* SugarCube support */
            Stat.prototype.clone = function() {
                return Stat.create(this);
            };
            Stat.prototype.toJSON = function() {
                return JSON.reviveWrapper('setup.Stat.create($ReviveData$)', Object.assign({}, clone(this)));
            };
        }
};
Stat.create = function(vals) {
    vals = vals || {};
    var result = new Stat();
    result._base = vals._base;
    result._mods = clone(vals._mods);
    result._current = vals._current;
    return result;
};

setup.Stat = Stat;