#257 Failed assertion in Array::left() when trying to access all elements

[Niklas Doose]

Trying to access all elements of an array via Array::left() produces the error:

Array::left(): Index out of range (in_range(n))

The same applies forArray::right(). Instead of the in_range() function the input should be checked to be positive and smaller or equal to ndata as done in the provided patch.