[Versa] statements function

[Michael Olson]

>
>> We still have the same problems with the "statement" function though.
>
> I don't think we should play games with argument-passing semantics for
> any function.  All function invocations should evaluate the expression
> provided for the argument, and pass the result.
>

I guess I don't see it as playing games, but defining what a filter  
expression means.  To me it is intended that a filter expression will  
have a different meaning the a pattern-expression, that's why I  
separated them.  Regardless of where it is located in a query

. < 18

to me means that it is working against a current context (that damn  
word again) node to evaluate, which further implies that where ever it  
is located it cannot be evaluated until the previous portions of the  
expression are evaluated.

This holds for the traverse operator.

Maybe it is as simple as saying

"in a traverse operator, . < 18 is short hand for (!x : $x < 18)"

Then, what I have been calling operator expressions can be promoted to  
be used else where, and they are evaluated like other expressions so  
you have

all() |- ns:age -> . < 18

translates to all resources over the age of 18 (based on what I said  
above)

and

statements(all(),ns:age,. < 18)

translates to the empty set because "." has no meaning (unless this  
query is within another query that defines dot but let's ignore that  
case for now).

and to get the same results as the filter operator you would need to do

statements(all(),ns:age,(!x : $x < 18))

I think I'm OK with this.

Mike

>
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Mike Olson                                                Principal  
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