User blog comment:Wythagoras/Dollar function formal definition/@comment-5529393-20130620132457

It still seems that a$[[0,1],1] doesn't match up with any rule.

For rule 9, I think you want some sort of shape after the a in a$[  △     ,0,a]_(b+1), otherwise there can only be one nonzero entry in the array. Also, are you sure you don't want commas after the triangles in

a$[  △     [...[   △     [   △     ,0,a-1]_(b+1),a-1]_b...]_b,a-1]_b

For example, under the current rules 3$[0,0,2]_2 = 3$[0[0[0[0,0,1]_2]]] - it seems more natural for it to be 3$[0,[0,[0,[0,0,1]_2]]].