Fwd: [vwnc] Introducing SimpleXPath

> Hi,
>
> during my work on the XML-Mapping framework SimpleXO, I realized that the
> XML querying code could be useful standalone, too. I factored out a
> library named SimpleXPath and made it available in Cincom public
> repository under the MIT license. It is similar to the XPath location path
> subset (without predicates) but offers some distinct features:
>
> - paths are built as pure Smalltalk expressions
> - extended wildcard support
> - simple API
>
> Example:
> (RootStep // 'source' /@ 'id')  "XPath: //source/@id"
>        contextNode: anXmlNode;
>        nodesDo: [:node | Transcript show: node stringValue; cr].
>
> The above code prints the 'id' value of all 'source' elements in the XML
> document from which anXmlNode is taken.
>
> I am interested in your opinions. I'd be glad If you give it a try and
> discuss your thoughts here. Below I've attached the package comment
> explaining the API, just in case. ;)
>
> Regards and happy coding!
> Steffen
>
>
>
>
> Simple XPath is an XML query library based on a subset of the XPath 1.0
> language. It provides a handy API to construct paths and a parser for
> abbreviated XPath location paths without predicates.
>
> See also: http://www.w3.org/TR/xpath/.
>
> I. NodeSets
> -----------------
> The result of constructing a path or parsing an XPath location path is a
> NodeSet. If applied to an XML node, a NodeSet provides access to the nodes
> selected by this set.
> 1. Call #contextNode: to define the node a NodeSet is applied to.
> 2. Call
>        #nodes to get a set of all matched nodes,
>        #nodesDo: with a one argument block to iterate over all matched nodes
> and
>        #selectNodes: with a one argument block to select some of the matched
> nodes.
> If you are working with tags that have prefixed names, ensure that you
> resolve the associated namespace before using a NodeSet.
> Call >>#resolveNamespaces: with a dictionary that maps all prefixes to
> their namespace.
>
> II. Path construction API:
> ------------------------------------
> To construct a path programmatically, use the Axis classes and the methods
>  from the protocol "path construction".
> 1. Single path steps:
>        ChildAxis ? 'name'.
> "select all child nodes tagged with 'name'"
>        ChildAxis ? ('prefix' + 'name').                        "select all
> child nodes tagged with
> 'prefix:name'"
>        AttributeAxis ? 'id'.
> "select all attribute nodes tagged with 'id'"
>
>        SelfAxis ? AnyNodeTest.                         "select the context
> node itself"
>        DescendantOrSelfAxis ? CommentTest.     "select all descendant
> comment nodes"
>
> 2. Concatenate steps with #/ :
>        (ChildAxis ? 'name') / (ChildAxis ? ('second' + 'name')).
>        (ChildAxis ? AnyNodeTest) / (AttributeAxis ? 'id').
>
>        "Often, the axis can be omitted:"
>        'name' / ('second' + 'name').                           "same as"
>                (ChildAxis ? 'name') / (ChildAxis ? ('second' + 'name')).
>        AnyNodeTest / (AttributeAxis ? 'id').           "same as"
>                (ChildAxis ? AnyNodeTest) / (AttributeAxis ? 'id').
>
>        "Similar to XPath, #/@, #// and #//@ abbreviate attribute and
> descendant-or-self steps:"
>        AnyNodeTest /@ 'id'.                                    "same as"
>                (ChildAxis ? AnyNodeTest) / (AttributeAxis ? 'id').
>        'name' // CommentTest.                                  "same as"
>                (ChildAxis ? 'name') / (DescendantOrSelfAxis ? AnyNodeTest) /
> (ChildAxis
> ? CommentTest).
>        'name' //@ 'id'.
>    "same as"
>                (ChildAxis ? 'name') / (DescendantOrSelfAxis ? AnyNodeTest) /
> (AttributeAxis ? 'id').
>
> 3. Query from the document root with a RootStep:
>        RootStep // AnyNodeTest.                                "all nodes"
>        RootStep //@ 'id'.                                              "id
> of each node"
>
> 4. Create the union of two NodeSets with #| :
>        (RootStep // 'element') | (RootStep // CommentTest).
>
>        "#\@ abbreviates the union with an attribute step:"
>        CommentTest \@ 'id'.                                    "same as"
>                (ChildAxis ? CommentTest) | (AttributeAxis ? 'id').
>
> 5. The wildcards # and * match single and multiple characters in local tag
> names:
>        ChildAxis ? 'name_##'.                                  "selects e.g.
> <name_01 />"
>        AttributeAxis ? '*_id'.                                 "selects e.g.
> ... svg_id='0x5' ..."
>        "NOTE: XPath allows * only for the whole tag name, e.g. //prefix:* "
>
> III. Parser API:
> --------------------
> To parse an abbreviated XPath location path, use SimpleXPathParser.
> However, predicate expressions are not supported.
> Call
>        #parseString: with the XPath string to parse that string and obtain a
> NodeSet and
>        #validateString: to check whether the string is free of syntax
> errors.
> If parsing fails, a SyntaxError is raised that gives the error position
> and a brief description.
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