MarkLogic 9 Product Documentationfn.subsequence
fn.subsequence( sourceSeq as Sequence, startingLoc as Number, [length as Number] ) as Sequence
Summary
Returns the contiguous sequence of items in the value of $sourceSeq beginning
at the position indicated by the value of $startingLoc and continuing for the
number of items indicated by the value of $length.
As described in https://www.w3.org/TR/xpath-functions/:
In the two-argument case, fn.subsequence returns a sequence comprising those items of
$sourceSeq whose index position (counting from one) is greater than or equal to the
value of $startingLoc (rounded to an integer):
$sourceSeq[fn:round($startingLoc) le $p]
No error occurs if $startingLoc is zero or negative.
In the three-argument case, The function returns a sequence comprising those items of
$sourceSeq whose index position (counting from one) is greater than or equal to the
value of $startingLoc (rounded to an integer), and less than the sum of
$startingLoc and $length (both rounded to integers):
$sourceSeq[fn:round($startingLoc) le $p and $p lt fn:round($startingLoc) + fn:round($length)]
No error occurs if $startingLoc is zero or negative, or if $startingLoc
plus $length exceeds the number of items in the sequence, or if
$length is negative.
Notes:
If $sourceSeq is the empty sequence, the empty sequence is returned.
If $startingLoc is zero or negative, the subsequence includes items from the beginning of the $sourceSeq.
If $length is not specified, the subsequence includes items to the end of $sourceSeq.
If $length is greater than the number of items in the value of $sourceSeq following $startingLoc, the subsequence includes items to the end of $sourceSeq.
The first item of a sequence is located at position 1, not position 0.
For detailed type semantics, see Section 7.2.13 The fn:subsequence functionFS.
The reason the function accepts arguments of type xs:double is that many computations on untyped data return an xs:double result; and the reason for the rounding rules is to compensate for any imprecision in these floating-point computations.
| Parameters | |
|---|---|
| sourceSeq |
A Sequence of items from which a subsequence will be
selected. If you pass in a single value,
it is treated as a Sequence with that single item; therefore, if you
pass in an array, fn.subsequence will treat the array as
a single-item sequence.
If you mean to get the subsequence of each item in the array, then
you can call xdmp.arrayValues
on the array.
|
| startingLoc | The starting position of the start of the subsequence. |
| length | The length of the subsequence. |
Example
const seq = xdmp.arrayValues(["item1", "item", "item3", "item4" , "..."]); fn.subsequence(seq, 4) => (item4, ...) const seq = xdmp.arrayValues(["item1", "item", "item3", "item4" , "..."]); fn.subsequence(seq, 3, 2) => (item3, item4)