void InspectIndex(Value value, out int index, out int span)
{
index = 1;
span = 1;
if (value is ScalarValue)
index = ((ScalarValue)value).IntValue;
else if (value is MatrixValue)
{
var M = (MatrixValue)value;
index = M[1].IntValue;
span = M.Length;
}
else
throw new YAMPArgumentWrongTypeException(value.Header, new string[] { "Matrix", "Scalar" }, "SubPlot");
}