SignificantDigits constructor
Creates a SignificantDigits instance with optional minimum and maximum significant digits.
Both minimum and maximum must be between 1 and 21, inclusive.
minimum must be less than or equal to maximum.
Implementation
SignificantDigits({this.minimum = 1, this.maximum = 21})
: assert(1 <= minimum && minimum <= 21),
assert(1 <= maximum && maximum <= 21),
assert(minimum <= maximum);