[augeas-devel] Distinguishing empty string from no value in path expressions

[Michael Chapman]

On Wed, 5 Oct 2011, David Lutterkort wrote:
> So far, nobody has needed that distinction, but it would be easy enough
> to add a null function to the language so that you could pick out nodes
> with null values, i.e. something like
>
>   match test/*[null(.)]
>
> which, in your example, would match /test/b

A null() function would be useful, however I'm not sure it should take a 
nodeset as an argument. It doesn't make sense for it to be applied to more 
than one node.

Perhaps it should be a no-argument predicate, "this node has no value".

Another question arises from all this: how would you match only non-null 
nodes?

- Michael