XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition (525 page)

BOOK: XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition
3.29Mb size Format: txt, pdf, ePub

Signature

Argument
Type
Meaning
sequence
xs:anyAtomicType*
The input sequence. Any untyped atomic values in the input are converted to
xs:double
values. The resulting sequence must consist entirely of numbers, or entirely of durations of the same kind.
Result
xs:anyAtomicType?
The average of the values in the input sequence. This will be a value of the same primitive type as the values in the input sequence. If the input values are
xs:integer
values, the result will be an
xs:decimal
.

Effect

If the input sequence is empty, the result is an empty sequence. This is not an error, even though a literal interpretation of the rules would involve dividing by zero.

In all other cases the result is the same as
sum($sequence) div count($sequence)
. Note that
$sequence
here is the atomized sequence generated by the function calling mechanism. If the sequence supplied in the call was a sequence of nodes, the number of atomic values is not necessarily the same as the number of nodes. For example, if
avg(@a)
is called to process a single attribute that is defined in the schema to contain a list of integers, then it will return the average of these integers.

The sequence of operations is as follows:

1.
The sequence supplied in the argument is atomized (this is a standard action of the function calling rules when the required type only allows atomic values).

2.
Any untyped atomic values in the resulting sequence (typically, values extracted from nodes in a schemaless document) are converted to
xs:double
values. If this conversion fails, a runtime error is reported.

3.
If the sequence now contains any NaN (not-a-number) values, the result of the
avg()
function is NaN.

4.
If the values are all numeric, they are summed according to the rules for the numeric
+
operator, which means that the result will depend on the types that are present in the sequence. If there is at least one
xs:double
, the sum will be an
xs:double
; otherwise, if there is an
xs:float
it will be an
xs:float
, otherwise
xs:decimal
or
xs:integer
.

5.
If the values are all durations, they are similarly summed according to the rules of the
+
operator. In consequence, it is not possible to mix the two duration types,
xs:dayTimeDuration
and
xs:yearMonthDuration
.

6.
Finally, the total is divided by the number of items using the
div
operator. In the case of a numeric total, this means that the average will be the same numeric type as the sum, unless the sum is an
xs:integer
in which case the average will be an
xs:decimal
. If the items are durations, the result will be a duration of the same type as the items.

The processor is allowed to use a different algorithm which might behave differently in the event of arithmetic overflow.

Examples

Expression
Result
avg((1.0, 2.6, 3.0))
xs:decimal(‘2.2’)
avg(())
()
avg((1, xs:float(‘3.5’), 5.5))
xs:float(‘3.3333333’)
avg((1, 2, 3))
xs:decimal(‘2.0’)
avg((xs:dayTimeDuration(‘P1D’), xs:dayTimeDuration (‘PT12H’)))
xs:dayTimeDuration (‘PT18H’)

See Also

count()
on page 733

max()
on page 830

min()
on page 830

sum()
on page 889

base-uri

The
base-uri()
function returns the base URI of a specific node in a document.

Signature

Argument
Type
Meaning
input-node
(optional)
node()?
The node whose base URI is required
Result
xs:string
The base URI of the node specified in the first argument, or the context node if there are no arguments

Other books

John Saturnall's Feast by Norfolk, Lawrence
Misfortune Cookie by Casey Wyatt
At Year's End (The 12 Olympians) by Gasq-Dion, Sandrine
Death of a Robber Baron by Charles O'Brien
Funland by Richard Laymon
Behind Our Walls by Chad A. Clark