XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition (350 page)

returns true. This applies even for peculiar cases like
NaN
: if the value of
$x
is
NaN
, then
$x eq $x
is false, while
$x ne $x
is true. Another reassuring feature of these operators is that if
$a eq $b
is true, then
$b eq $a
is also true. (It's worth mentioning these things because as we'll see later in the chapter, when it comes to the
=
and
!=
operators it's best not to make any assumptions).

The other four operators in this group,
lt
,
le
,
gt
, and
ge
, work only for data types that are ordered. The data types that have an ordering, and the way the ordering works, are defined in the table below.