Hi Günther,

Thanks for the concise bug report. I stumbled across a similar issue just recently [1], so I’m glad to confirm that the latest BaseX 9.0 snapshot returns the correct result [2].

All the best, Christian

[1] https://github.com/BaseXdb/basex/commit/ab52f2dde2628bbeac5da22898bf6e28f682... [2] http://files.basex.org/releases/latest/

On Mon, Oct 30, 2017 at 8:25 PM, Gunther Rademacher grd@gmx.net wrote:

While testing some XQuery lookup expressions on BaseX 8.6.7, I got a wrong result for this one:

  (map{'a':(1,3)},map{'a':(2,4)})!?a[2]

It should have returned the second item of the 'a' entry for each of the maps, i.e.

  3 4

but it returns just

  3

Apparently the predicate is applied as if everything before it was in parentheses, i.e. as if it were

  ((map{'a':(1,3)},map{'a':(2,4)})!?a)[2]

The (simplified) parse tree for the original expression and the XQuery 3.1 grammar however indicates that the predicate is part of the mapping target expression:

 <SimpleMapExpr>
     <ParenthesizedExpr>
        ...
     </ParenthesizedExpr>
     <TOKEN>!</TOKEN>
     <PostfixExpr>
        <UnaryLookup>
           <TOKEN>?</TOKEN>
           <NCName>a</NCName>
        </UnaryLookup>
        <Predicate>
           <TOKEN>[</TOKEN>
           <IntegerLiteral>2</IntegerLiteral>
           <TOKEN>]</TOKEN>
        </Predicate>
     </PostfixExpr>
  </SimpleMapExpr>

Best regards Gunther