BigFixed.opBinary

auto b1 = BigFixed(1, 10);
assert((b1 / BigFixed(4, 10)).toDecimalString(2) == "0.25");
assert((b1 + BigFixed(2, 10)).toDecimalString(2) == "3.00");
assert((b1 * BigFixed(2, 10)).toDecimalString(2) == "2.00");
assert((b1 - BigFixed(1, 10)).toDecimalString(2) == "0.00");