XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition (450 page)
Read XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition Online
Authors: Michael Kay
keyword can use all variables declared in previous clauses of the expression (but not the variable ranging over that expression itself).
For example:
some $p in //price satisfies $p > 10000
is true if there is a
every $p in //price satisfies $p > 10000
is true if every
The result of the expression (unless some error occurs) is always a single
xs:boolean
value.
The
satisfies
expression is evaluated to return a boolean value. This evaluation returns the
effective boolean value
of the expression, using the same rules as for the
boolean()
function and the condition in anifexpression. For example, if the result of the expression is a string, the effective boolean value is
true
if the string is not zero-length. The expression will almost invariably reference each one of the range variables, although the results are still well defined if it doesn't.
As with
for
expressions,someandeveryexpressions do not change the context item. This means that the following is wrong (it's not an error, but it doesn't produce the intended answer):
(:wrong:) some $i in //item satisfies price > 200
It should be written instead:
(:correct:) some $i in //item satisfies $i/price > 200
Note that if the input sequence is empty, thesomeexpression will always be
false
, while theeveryexpression will always be
true
. This may not be intuitive to everyone, but it is logical—theeveryexpression is true if there are no counter-examples; for example, it's true that every unicorn has one horn, because there are no unicorns that don't have one horn. Equally, and this is where the surprise comes, it is also true that every unicorn has two horns.
