ARTICLE: "xml.traversal""Utilities for traversing XML"
"The " { $vocab-link "xml.traversal" } " vocabulary provides utilities for traversing an XML DOM tree and viewing the contents of a single tag. The following words are defined:"
ARTICLE: { "xml.traversal""intro" } "An example of XML processing"
"To illustrate how to use the XML library, we develop a simple Atom parser in Factor. Atom is an XML-based syndication format, like RSS. To see the full version of what we develop here, look at " { $snippet "basis/syndication" } " at the " { $snippet "atom1.0" } " word. First, we want to load a file and get a DOM tree for it."
{ $code <" "file.xml" file>xml "> }
"No encoding descriptor is needed, because XML files contain sufficient information to auto-detect the encoding. Next, we want to extract information from the tree. To get the title, we can use the following:"
{ $code <" "title" tag-named children>string "> }
"The " { $link tag-named } " word finds the first tag named " { $snippet "title" } " in the top level (just under the main tag). Then, with a tag on the stack, its children are asserted to be a string, and the string is returned." $nl
"For a slightly more complicated example, we can look at how entries are parsed. To get a sequence of tags with the name " { $snippet "entry" } ":"
{ $code <" "entry" tags-named "> }
"Imagine that, for each of these, we want to get the URL of the entry. In Atom, the URLs are in a " { $snippet "link" } " tag which is contained in the " { $snippet "entry" } " tag. There are multiple " { $snippet "link" } " tags, but one of them contains the attribute " { $snippet "rel=alternate" } ", and the " { $snippet "href" } " attribute has the URL. So, given an element of the sequence produced in the above quotation, we run the code:"
