All the tests that can usually be applied to attributes can be used with any identification of an attribute,
where the attribute is identified by using the attribute's name, using an attribute alias name, or selecting an
item of the attributes shelf.
Because all attributes of specified attributes are, by definition, specified, the is
specified, is defaulted, and is implied tests do not make much sense when
applied to it: is specified always succeeds, and is defaulted and is
implied always fail.
For example, the following repeat over loop outputs only those attributes whose values are
defaulted or specified (excluding those which are implied or unspecified) and whose values consist entirely of
letters. The attributes are output in the order in which they are declared. This is accomplished by testing an
attribute identified by an attribute alias name:
process do sgml-parse document scan #main-input output "%c" done element #implied output "<%q" repeat over attributes as a do when attribute a isnt implied & attribute a matches (letter+ value-end) output "%_" || key of attribute a || "=%"" || attribute a || "%"" done again output ">%n%sc%sn</%q>%sn"
Running this program on the following input
<!doctype a [
<!element a - - (b+)>
<!attlist a a1 nutoken #implied
a2 cdata "strawberries">
<!element b - - (c+)>
<!attlist b c1 cdata "potato jam"
c2 cdata "kiwi">
<!element c - - (#pcdata)>
<!attlist c c1 cdata #implied
c2 cdata "apples">
]>
<a>
<b>
<c>Text
</c>
</b>
</a>
produces this output:
<A A2="strawberries">
<B C2="kiwi">
<C C2="apples">
Text
</C>
</B>
</A>