object[b] is a structured type (array in this case: ``[1,2,3]``) according to [rfc4627](http://tools.ietf.org/html/rfc4627) and it was deemed that ``cfengine/core`` functions that interface with data containers should not recurse into said structured types. See [redmine#3279](https://cfengine.com/dev/issues/3279#note-18) and this [issue comment](https://github.com/cfengine/core/pull/1056#issuecomment-27310002) as well as the two comments that follow it.

I hope the above makes sense.

@tzz If you think I've missed something, or have anything else to add, could you expand on this?