static realPartOf(v) {
        if (v instanceof Complex) {
            return v.real;
        }
        if (typeof v === "number") {
            return v;
        }
        throw new DetailedError("Unrecognized value type.", {v});
    }
Returns the real component of a Complex, integer, or float value.
@param {!number|!Complex} v
@returns {!number}