XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition (459 page)

BOOK: XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition
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Both the
cast
as
and
castable
as
operators perform atomization on the supplied value. This means that if the supplied value is a node, its typed value is first extracted. If the operand (after atomization) is a sequence of more than one item, then a type error occurs in the case of
cast
as
, or the value
false
is returned in the case of
castable
as
.

There is a shorthand for a
cast
as
expression, which is to use a constructor function. For example, the expression
@A
cast
as
xs:integer?
can be rewritten as a function call,
xs:integer(@A)
. There is a constructor function available for every built-in atomic type, and for every named atomic type in an imported schema, and its effect is identical to using the
cast
as
expression with the
?
option (that is, if an empty sequence is supplied to a constructor function, it returns an empty sequence). The only cases where you need to use the full
cast
as
expression are:

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