operator
true if the previous element is the specified element, and false otherwise.
Replacing is with isnt reverses the result.
previous (of element-expression)? (is | isnt) namespace-modifier? (element-name | element-name-list)
previous is tests whether the previous sibling of the current element of the currently-active parse is
an instance of the element element-name, or one of the elements listed in element-name-list.
element-name-list is a parenthesized list of elements, separated by |. Replacing
is with isnt will reverse these results.
If element-expression is not specified, the test applies to the previous sibling element of the current element. If element-expression is specified, the test applies to the previous sibling element of the element specified by element-expression.
You can specify the name dynamically by using the identity operator (~) followed by a string expression: for example, to check for elements with a previous sibling element of the same name as
the current element,
element #implied when previous is ~(name of element) suppress
The previous is test ignores inclusions and data content.