Package xpath-sys

The XPATH-SYS package provides an API for extensions to Plexippus XPath.

About This Package

Pipes
Node sets
Implementing environments
Defining extension functions
Profiling support
Miscellaneous functions

Pipes

Pipes are lazy lists, inspired by their implementation in Norvig's 'Paradigms of Artificial Intelligence Programming'.

Macro make-pipe (head tail)

Constructs a pipe (lazy list). ...

Function pipe-head (pipe)

Returns the head of the pipe.

Function pipe-tail (pipe)

Returns the tail of the list. ...

Node sets

Node sets are the XPath data type used to represent the results of evaluations that select multiple nodes. As sets, they never contain duplicates. Conceptually, they are unordered, with the most important order defined on them being the document order.

As a data structure though, node sets are backed by a pipe, and the order of elements in that pipe is well-documented: By default, the pipe of returned node sets is sorted into document order. When unordered results are requested, the order is usually not specified, but in some cases, are already sorted according to the axis being queried, which is usually sorted either in document order,or in reverse document order. See xpath:evaluate for the unordered argument.

Function make-node-set (pipe &optional (ordering unordered))

Makes a node set containing nodes from the pipe with specified ordering.

Function pipe-of (node-set)

Returns the pipe that contains the elements of the node-set.

Implementing environments

Environments provide compilation-time configuration for XPath. An environment is a CLOS object, which is queried by the compiler using generic functions that users can implement on their own subclasses of xpath::environment.

The default environment class implements a `dynamic' environment, backed by information bound in dynamic variables, so that typical uses of XPath work without special environment classes.

Function environment-find-namespace (environment prefix)

Returns namespace URI for specified prefix.

Function environment-find-variable (environment local-name uri)

Finds an XPath variable by local-name and uri ...

Function environment-find-function (environment local-name uri)

Finds an XPath function by local-name and uri ...

Defining extension functions

XPath defines built-in functions in the empty namespace. Using the extension API, user code can implement XPath functions addressed using other namespaces.

Macro define-extension (name uri &optional documentation)

Defines an XPath extension with specified name and uri. ...

Macro define-xpath-function/lazy (ext name args &body body)

Defines an XPath function, "lazy" style. ...

Macro define-xpath-function/eager (ext name args &body body)

Defines an XPath function, "eager" style. ...

Macro define-xpath-function/single-type (ext name type args &body body)

Defines an XPath function, "eager" style with automatic type conversion. ...

Function find-xpath-function (local-name uri)

Performs an XPath function lookup using standard lookup rules ...