.. _subsequence:

===========
subsequence
=========== 

A portion of a sequence based on a starting point and length

Description
~~~~~~~~~~~
The fn:subsequence function returns a sequence of $length items of $sourceSeq, 
starting at the position $startingLoc. The first item in the sequence is 
considered to be at position 1, not 0. If no $length is passed, or if $length is 
greater than the number of items that can be returned, the function includes 
items to the end of the sequence. An alternative to calling the fn:subsequence 
function is using a predicate. For example, fn:subsequence($a,3,4) is equivalent 
to $a[position() = (3 to 7)].

.. list-table::
   :widths: 40 60
   :header-rows: 1

   * - **Parameters**
     - **Description**
   * - sourceSeq:item()
     - the entire sequence
   * - startingLoc:double()
     - the starting item position (1-based)
   * - length:double()
     - the number of items to include

Examples
~~~~~~~~
.. list-table::
   :widths: 50 50
   :header-rows: 1

   * - **XPath**
     - **Results**
   * - subsequence(('a', 'b', 'c', 'd', 'e'), 3)
     - ('c', 'd', 'e')
   * - subsequence(('a', 'b', 'c', 'd', 'e'), 3, 2)
     - ('c', 'd')
   * - subsequence(('a', 'b', 'c', 'd', 'e'), 3, 10)
     - ('c', 'd', 'e')
   * - subsequence(('a', 'b', 'c', 'd', 'e'), 10)
     - ()
   * - subsequence(('a', 'b', 'c', 'd', 'e'), -2, 5)
     - ('a', 'b')
   * - subsequence( (), 3)
     - ()