Question

I have this list:

• ADD X
• ADD Y
• REMOVE Z
• ADD X
• NO ACTION Y

I need of this results:

• ADD X
• NO ACTION Y
• REMOVE Z

The rules to calculate the delta are these:
I have 3 action (ADD, REMOVE, NO ACTION)

1. ANY ACTION * NO ACTION = NO ACTION
2. ADD * REMOVE or REMOVE * ADD = NO ACTION
3. SAME ACTION * SAME ACTION = SAME ACTION

The problem is that I implement this with a functional language (XQuery). I found a logic, based on fn:distinct-values. But the last rule (3) is unsatisfied.

Thanks in advance!!

Answer 1

Finally I found the way. I hope that this is good.

These are my first experiments with XQuery and I need to remeber what I have under my fingers and what possibilities this language offer.

My problem is data that came in. And I decide to transformate the information in a structure that can I easily manipulate.

A golden brick to solve this is this example about grouping data :

for $d in distinct-values(doc("order.xml")//item/@dept)
let $items := doc("order.xml")//item[@dept = $d]
order by $d
return <department code="{$d}">{
     for $i in $items
     order by $i/@num
     return $i
   }</department>

After this I used this algorithm:
0. If the count of action == 1 -> take first action
1. else If exist almost ONE – NO ACTION -> NO ACTION (RULE 1)
2. else If exist ADD and REMOVE in same list -> NO ACTION (RULE 2)
3. else take the first action (equal actions)

For this I borrowed a function from functx library:

declare function local:is-value-in-sequence( $value as xs:anyAtomicType? ,$seq as      xs:anyAtomicType* )  as xs:boolean {
 $value = $seq
 };

Simple but effective.

Thanks a lot for all!