#66 `ew` raises too many exceptions

[Dennis]

[1]2ew raising an invalid slice size exception means you cannot use 2ew if you don't the array length beforehand.

I'd expect 2ew to behave like [_\1>]zW<, so Array Long ew should just return an empty array if the Long is longer than the Array.

Also, negative slice sizes could be used to reverse slices inner order:

[1 2 3]-2ew e# Gives [[2 1] [3 2]]

[Martin Büttner]

Here is another generalisation that seems useful and would have saved me a dozen bytes or more just now:

[[1 2 3]
 [4 5 6]
 [7 8 9]] [2 2] ew

which would give

[[[[1 2][4 5]] [[2 3][5 6]]]
 [[[4 5][7 8]] [[5 6][8 9]]]]

That is [m n] would give a grid of all m x n sub-blocks. This would easily generalise to arbitrary dimensions, but it seems most useful for processing ASCII grids.

[Sp3000]

Here's another use case for Array Long ew giving empty array when Long is larger than the length of the Array: link

[aditsu]

I've implemented the "return empty array if the number is too large" part