.. _sum:

===
sum
=== 

The sum of values in a sequence

Description
~~~~~~~~~~~
The fn:sum function sums the values in a sequence. The $arg sequence can contain 
a mixture of numeric and untyped values. Numeric values are promoted as 
necessary to make them all the same type. Untyped values are cast as numeric 
xs:double values.

The function can also be used on duration values, so the $arg sequence can 
contain all xs:yearMonthDuration values or all xs:dayTimeDuration values (but 
not a mixture of the two). 

The $zero argument allows you to specify an alternate value for the sum of the 
empty sequence. If $arg is the empty sequence, and $zero is provided, the 
function returns $zero. The $zero argument could be the empty sequence, the 
integer 0, the value NaN, a duration of zero seconds, or any other atomic value. 

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

   * - **Parameters**
     - **Description**
   * - arg:numeric()
     - 
   * - zero:numeric()
     - 

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

   * - **XPath**
     - **Results**
   * - sum( (1, 2, 3) )
     - 6
   * - sum($ordDoc//item/@quantity)
     - 7
   * - sum($ordDoc//item/@dept)
     - Error FORG0001
   * - sum( (xs:yearMonthDuration('P1Y2M'), xs:yearMonthDuration('P2Y3M')) )
     - P3Y5M
   * - sum( (1, 2, 3, () ) )
     - 6
   * - sum( (1, 2, xs:yearMonthDuration('P1Y')) )
     - Error FORG0006
   * - sum( () )
     - 0
   * - sum( (), () )
     - ()

See Also
~~~~~~~~

.. toctree::
   :titlesonly:
   :glob:

* :ref:`count`.
* :ref:`avg`.