[kd0amg]

Yeah, ok, array slicing, woohoo. But what's interesting here is that this doesn't come from any special/privileged syntax or from special handling by the { operator. The { operator just expects a scalar and a list and accesses an element of the list according to the scalar. This slicing capability simply falls out of the automatic lifting J does when you pass an array of higher rank than the operator expects, the same rule that gives you (2 5 3)+7 = (9 12 10).