XPath Datatypes
An XPath expression returns one of four datatypes:
-
node-set
Represents a set of nodes. The set can be empty, or it can contain any number of nodes.
-
boolean
Represents the value
true
orfalse
. Be aware that thetrue
orfalse
strings have no special meaning or value in XPath; see Section 4.2.1.2 in Chapter 4 for a more detailed discussion of boolean values.-
number
Represents a floating-point number. All numbers in XPath and XSLT are implemented as floating-point numbers; the
integer
(orint
) datatype does not exist in XPath and XSLT. Specifically, all numbers are implemented as IEEE 754 floating-point numbers, the same standard used by the Javafloat
anddouble
primitive types. In addition to ordinary numbers, there are five special values for numbers: positive and negative infinity, positive and negative zero, andNaN
, the special symbol for anything that is not a number.-
string
Represents zero or more characters, as defined in the XML specification.
These datatypes are usually simple, and with the exception of node-sets, converting between types is usually straightforward. We won’t discuss these datatypes in any more detail here; instead, we’ll discuss datatypes and conversions as we need them to do specific tasks.
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