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Bug #5110
closed
XPDY0002 The context item is absent, so position() is undefined for use of position() inside predicate
Start date:
2021-09-30
Due date:
% Done:
100%
Estimated time:
Legacy ID:
Applies to branch:
10, 11, trunk
Fix Committed on Branch:
10, trunk
Description
I get the error
Error on line 8 column 29 of powerset1.xq:
XPDY0002 The context item is absent, so position() is undefined
Focus: absent
Local variables
$counter = 0
$input = ("A", "B", "C", ... [4])
$counter-bin = xs:base64Binary("AA==")
invoked by unknown caller (class net.sf.saxon.value.MemoClosure)
Focus: absent
Local variables
$counter = 0
$input = ("A", "B", "C", ... [4])
invoked by function call at file:/C:/Users/Martin%20Honnen/OneDrive/Documents/XQuery/powerset/./powerset1.xq#17
Focus: absent
Local variables
$a = []
$i = 0
$input = ("A", "B", "C", ... [4])
invoked by unknown caller (class net.sf.saxon.functions.hof.UserFunctionReference$BoundUserFunction)
running Saxon 10.6 EE Java against the XQuery
declare namespace math = 'http://www.w3.org/2005/xpath-functions/math';
declare namespace bin = 'http://expath.org/ns/binary';
declare namespace array = 'http://www.w3.org/2005/xpath-functions/array';
declare function local:combination($counter as xs:integer, $input as item()*) as item()* {
let $counter-bin := bin:from-octets($counter)
return $input[
let $j:= position() - 1,
$bin := bin:and($counter-bin, bin:shift(bin:hex('1'), $j))
return bin:to-octets($bin) > 0]
};
declare function local:powerset($input as item()*) as array(item()*) {
fold-left(
0 to (xs:integer(math:pow(2, count($input))) - 1),
[],
function($a, $i) { array:append($a, local:combination($i, $input)) }
)
};
local:powerset(('A', 'B', 'C', 'D'))
The code runs fine with BaseX, outputting [(), "A", "B", ("A", "B"), "C", ("A", "C"), ("B", "C"), ("A", "B", "C"), "D", ("A", "D"), ("B", "D"), ("A", "B", "D"), ("C", "D"), ("A", "C", "D"), ("B", "C", "D"), ("A", "B", "C", "D")].
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