Hi Christian,

Elaborating on the issue below and just thinking out loud.

Would it make sense having to opportunity to evaluate a function body lazily?

Consider the following function:

declare function item:exists

      ( $item

      , $existProcessor

      , $emptyValue

      )

      { if ( exists( $item))

        then $existProcessor( $item)

        else $emptyValue

      } ;

Even when called with an existing: $item, $emptyValue will be evaluated what could be an expensive evaluation.

Having the possibility of lazy evaluation of the function body would prevent this.

I’ve two questions:

- does the above make sense?

- does it make enough sense to be implemented in basex?

If implemented: for keeping the code clean, specifying this laziness should be done within the function, not within the function call.

I tumbled on the %basex:inline-annotation for global variables. This would do very nicely for specifying laziness for evaluating function bodies.

declare %basex:inline function item:exists

      ( $item

      , $existProcessor

      , $emptyValue

      )

      { if ( exists( $item))

        then $existProcessor( $item)

        else $emptyValue

      } ;

Best,

Rob

Van: Christian Grün [mailto:christian.gruen@gmail.com]
Verzonden: woensdag 13 mei 2015 12:36
Aan: Rob Stapper; BaseX
Onderwerp: Re: [basex-talk] unexpected behaviour