XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition (441 page)
Read XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition Online
Authors: Michael Kay
We'll look first at
for
expressions that operate on a single sequence and then move on to the more general case where there are multiple input sequences.
Mapping a Sequence
When used with a single sequence, theforexpression applies the expression in thereturnclause to each item in the input sequence. The relevant item in the input sequence is accessed not as the context item but as the value of the variable declared in theforclause.
These variables are referred to as range variables, to distinguish them from variables supplied from outside the XPath expression, such as variables declared in an XSLT stylesheet. The term comes originally from the branch of mathematical logic called predicate calculus.
In most cases the expression in thereturnclause will depend in some way on the range variable. In other words, thereturnvalue is a function of the range variable, which means we can rewrite theforexpression in the abstract form:
