namespace System.Numerics
{
    public interface INumber<TSelf> : IComparable, IComparable<TSelf>, IEquatable<TSelf>, IFormattable, IParsable<TSelf>, ISpanFormattable, ISpanParsable<TSelf>, IUtf8SpanFormattable, IUtf8SpanParsable<TSelf>, IAdditionOperators<TSelf, TSelf, TSelf>, IAdditiveIdentity<TSelf, TSelf>, IComparisonOperators<TSelf, TSelf, bool>, IDecrementOperators<TSelf>, IDivisionOperators<TSelf, TSelf, TSelf>, IEqualityOperators<TSelf, TSelf, bool>, IIncrementOperators<TSelf>, IModulusOperators<TSelf, TSelf, TSelf>, IMultiplicativeIdentity<TSelf, TSelf>, IMultiplyOperators<TSelf, TSelf, TSelf>, INumberBase<TSelf>, ISubtractionOperators<TSelf, TSelf, TSelf>, IUnaryNegationOperators<TSelf, TSelf>, IUnaryPlusOperators<TSelf, TSelf>
        where TSelf, INumber<TSelf>?
    {
        static virtual int Sign(TSelf value);
    }
}