attribute is implied


Return type:
Returns true when the attribute has no set value, and false otherise. Replacing is with isnt reverses the result.
attribute attribute-name (of element-expression)? (is | isnt) implied


The is implied attribute type test succeeds when the referenced element or data attribute has no set value, either in the start tag or in the element declaration. Otherwise, the test fails. Using isnt instead of is reverses the results.

For example:

  repeat over attributes as a
     output key of attribute a || "=%"%v(a)5"%n"
        when attribute a isnt implied

Unlike most other attribute references, no error occurs if the specified attribute doesn't exist, or was not given a value, since the test does not actually use the value.

If the element-expression references an element that does not exist, or the specified attribute is not declared, the is form of the test always fails, and the isnt form always succeeds.