private static Result Cut(Evaluator.Args args)
{
var separator = args.ToString(args.GetSwitch("d") ?? " \t\r\n");
var fieldsValue = args.GetSwitch("f");
var fields = fieldsValue != null
? args.Preview(args.ToScalar(fieldsValue))
: "1";
var fieldIndices = new HashSet <int>(fields
.Split(',')
.SelectMany(f => int.TryParse(f, out var idx) ? new[] { idx - 1 } : new int[0]));
return(args
.Flatten()
.Select(obj => string
.Join(
separator,
args
.Preview(obj)
.Split(separator.ToCharArray(), StringSplitOptions.RemoveEmptyEntries)
.Where((_, idx) => fieldIndices.Contains(idx)))
.Trim())
.Where(s => s.Length > 0)
.ToArray());
}