private static Tuple <T, DataType> Uncons(DataType dataType)
{
if (dataType is One one)
{
if (RList <Tuple <T, T> > .IsEmpty(one.RList))
{
return(new Tuple <T, DataType>(one.Alpha, Empty));
}
return(new Tuple <T, DataType>(one.Alpha, new Zero(one.RList)));
}
if (dataType is Zero zero)
{
var xy = RList <Tuple <T, T> > .Head(zero.RList);
var psp = RList <Tuple <T, T> > .Tail(zero.RList);
return(new Tuple <T, DataType>(xy.Item1, new One(xy.Item2, psp)));
}
throw new ArgumentException("must be Zero or One", nameof(dataType));
}
