| This iterator is a wrapper that always returns the position of
a node in document order. It is needed for the case where
a call to position() occurs in the context of an XSLT element
such as xsl:for-each, xsl:apply-templates, etc.
The getPosition() methods in DTMAxisIterators defined
in DTMDefaultBaseIterators always return the position
in document order, which is backwards for XPath in the
case of the ancestor, ancestor-or-self, previous and
previous-sibling.
XSLTC implements position() with the
BasisLibrary.positionF() method, and uses the
DTMAxisIterator.isReverse() method to determine
whether the result of getPosition() should be
interpreted as being equal to position().
But when the expression appears in apply-templates of
for-each, the position() function operates in document
order.
The only effect of the ForwardPositionIterator is to force
the result of isReverse() to false, so that
BasisLibrary.positionF() calculates position() in a way
that's consistent with the context in which the
iterator is being used."
(Apparently the correction of isReverse() occurs
implicitly, by inheritance. This class also appears
to maintain its own position counter, which seems
redundant.) |
