Generated: Monday, November 14, 2011, 09:19:50 Copyright © 2011 , Kurt NÝrmark The local LAML software home page

Reference Manual of the XML parser and pretty printer for LAML

Kurt NÝrmark © normark@cs.aau.dk Department of Computer Science, Aalborg University, Denmark.

LAML Source file: tools/xml-html-support/xml-support.scm

This is a simple, non-validating XML parser for LAML together with XML pretty printing support. As of the current version, the parser is not complete. Nevertheless, it is useful tool for parsing most everyday XML documents to a Lisp data structure.

Given a well-formed XML document this parser returns a Lisp tree structure that represents the parse tree of the XML document. The parser handles start tags, end tags, and empty tags (in this parser called start-end tags). Entities and their declarations are not handled at all.

The top level functions are xml-parse and xml-parse-file. The xml-parser can be loaded as a library as well.

There exists elucidative documentation of this parser. See also the HTML parsing and pretty printing support, which is built on top of the XML tools, and the illustrative examples of the XML parser and pretty printer.

This tool assumes that laml.scm and the general library are loaded. The tool loads the collect-skip and the file-read libraries.

The typographical rebreaking and re-indenting of running text is still missing.

The LAML interactive tool procedures xml-pp and xml-parse in laml.scm are convenient top-level pretty printing and parse procedures respectively.

Please notice that this is not a production quality parser and pretty printer! It is currently used for internal purposes.

From LAML version 20, the XML pretty printing in lib/xml-in-laml/xml-in-laml.scm replaces the XML pretty printing in this library.

Table of Contents:
1. The format of the parse tree. 4. AST-level parser functions. 7. Variables that control the pretty printing.
2. Constants. 5. Utility parser functions. 8. Parse tree conversions.
3. Native low-level level parser functions. 6. Top level XML pretty printing functions.

Alphabetic index:
collect-attributes-in-tree (collect-attributes-in-tree tree attr-key) Traverse the parse tree, tree, and return the list all attribute values of the attribute attr-key found in the tree.
indentation-delta indentation-delta An integer which gives the level of indentation
is-tag-of-kind? (is-tag-of-kind? tag-kind) Return a predicate which tests whether a subtree or node is of tag-kind (a symbol or string).
parse-tree-to-ast (parse-tree-to-ast pt language) Convert a HTML/XML parse tree to a LAML abstract syntax tree in language.
parse-tree-to-element-structure (parse-tree-to-element-structure pt) Convert a HTML/XML parse tree to an element structure ala LENO.
parse-tree-to-laml (parse-tree-to-laml tree output-file) Transform an XML or HTML parse tree to a similar surface LAML expression on output-file.
parse-xml (parse-xml file-path) This function parses a file and returns the parse tree.
parse-xml-file (parse-xml-file in-file-path out-file-path) Top level parse function which takes an XML file name as input, and delivers a parse tree on out-file-path.
parse-xml-file-to-ast (parse-xml-file-to-ast in-file-path out-file-path xml-language) Top level parse function which takes an XML file name as input, and delivers an XML-in-LAML AST on out-file-path.
parse-xml-string (parse-xml-string xml-string) This function parses a string with XML contents and returns the parse tree.
parse-xml-string-to-ast (parse-xml-string-to-ast xml-string xml-language) This function parses a string with XML contents and returns an XML-in-LAML AST.
parse-xml-to-ast (parse-xml-to-ast file-path xml-language) This function parses an XML file and returns the corresponding XML-in-LAML AST.
parser-status (parser-status) Display parser status in case of error in the parse process.
prefered-maximum-width prefered-maximum-width An integer that expresses the preferred maximum column width
pretty-print-xml-parse-tree (pretty-print-xml-parse-tree parse-tree) Pretty prints a HTML parse tree, and return the result as a string.
pretty-print-xml-parse-tree-file (pretty-print-xml-parse-tree-file in-file-path [out-file-path]) Pretty prints the XML parse tree (Lisp file) in in-file-path.
resulting-parse-tree resulting-parse-tree A global varible holding the latest produced parse tree
traverse-and-collect-from-parse-tree (traverse-and-collect-from-parse-tree tree node-interesting? result-transformer) Traverse the parse tree, tree, and return a list of result-transformed nodes that satisfy the node-interesting? predicate in the parse tree.
use-single-lining use-single-lining A boolean which controls the application of single line pretty printing.
white-space-preserving-tags white-space-preserving-tags A list of tag names for which white space is preserved.
xml-parser-preserve-white-space xml-parser-preserve-white-space A constant that controls if white space is uniformly preserved by the XML parser.


1 The format of the parse tree.
A parse tree T produced by this tool is of the form
    (tree N ST1 ST2 ... STn) 
where STi, i=1..n are parse trees (recursively) and N is a node (see below).

A leaf node N may be of the form

    (tree N) 
or just N if N is a string (corresponding to textual contents) or an empty tag (a tag without contents).

An inner node of a parse tree corresponds to a tag (an element) with contents. Such a node is represented by the following 'tag structure':

    (tag kind tag-name . attr-info) 
tag is a symbol (for tagging). kind is either start or start-end (both symbols). tag-name is a string. Attr-info is the attribute on property list format.

A terminal node may be a start-end node, a comment node or just a contents string. End tags are not represented in the parse tree.

Here is an example of a start-end node (empty node) with two properties:

    (tag start-end "title" role "xxx" size "5") 
Comments are represented as comment nodes of the form
    (comment comment-string) 

Declaration nodes of the form

    (declaration kind value) 
are also possible. They are for instance used for document type (???) information in HTML. Finally nodes of the form
    (xml-declaration attribute-property-list) 
are supported.


2 Constants.
Constants that affect the working of the parser.

xml-parser-preserve-white-space
Form xml-parser-preserve-white-space
Description A constant that controls if white space is uniformly preserved by the XML parser.
See also Scheme source file xml-parser-preserve-white-space

white-space-preserving-tags
Form white-space-preserving-tags
Description A list of tag names for which white space is preserved. A list of strings. No angle brackets ('<' or '>')should be given in the names. Must be assigned to the appropriate value before a parse function is called.
See also Scheme source file white-space-preserving-tags


3 Native low-level level parser functions.
The top level parser functions in this section deliver specialized low level parse trees (in some ad hoc list structure).

parse-xml-file
Form (parse-xml-file in-file-path out-file-path)
Description Top level parse function which takes an XML file name as input, and delivers a parse tree on out-file-path. file-path is a file path (relative or absolute) with or without an extension. The default extension is xml. The parse tree is written on the file out-file-path.
See also Scheme source file parse-xml-file

parse-xml
Form (parse-xml file-path)
Description This function parses a file and returns the parse tree. file-path is a file path (relative or absolute) without any extension.
Returns The parse tree in the original, low level parse tree format (a list structure)
See also Scheme source file parse-xml

parse-xml-string
Form (parse-xml-string xml-string)
Description This function parses a string with XML contents and returns the parse tree. xml-string is a string with xml contents
Returns The parse tree in the original, low level parse tree format (a list structure)
See also Scheme source file parse-xml-string


4 AST-level parser functions.
The top level parser functions in this section deliver XML-in-LAML abstract syntax trees. These trees are much more useful than the low-level parse trees delivered by the functions in the previous section.

parse-xml-file-to-ast
Form (parse-xml-file-to-ast in-file-path out-file-path xml-language)
Description Top level parse function which takes an XML file name as input, and delivers an XML-in-LAML AST on out-file-path. The AST is written on the file out-file-path.
Parameters in-file-path a file path (relative or absolute) with or without an extension. The default extension is xml.
out-file-path path the output file.
xml-language the name of the XML language in LAML, to which the resulting AST belongs. A symbol.
See also Scheme source file parse-xml-file-to-ast

parse-xml-to-ast
Form (parse-xml-to-ast file-path xml-language)
Description This function parses an XML file and returns the corresponding XML-in-LAML AST.
Parameters file-path a file path (relative or absolute) without any extension.
xml-language the name of the XML language in LAML, to which the resulting AST belongs. A symbol.
Returns An XML-in-LAML AST.
See also Scheme source file parse-xml-to-ast

parse-xml-string-to-ast
Form (parse-xml-string-to-ast xml-string xml-language)
Description This function parses a string with XML contents and returns an XML-in-LAML AST.
Parameters xml-string a string with xml contents.
xml-language the name of the XML language in LAML, to which the resulting AST belongs. A symbol.
Returns An XML-in-LAML AST.
See also Scheme source file parse-xml-string-to-ast

resulting-parse-tree
Form resulting-parse-tree
Description A global varible holding the latest produced parse tree
See also Scheme source file resulting-parse-tree


5 Utility parser functions.
The functions in this section are all miscelaneous and utility functions of the parser.

traverse-and-collect-from-parse-tree
Form (traverse-and-collect-from-parse-tree tree node-interesting? result-transformer)
Description Traverse the parse tree, tree, and return a list of result-transformed nodes that satisfy the node-interesting? predicate in the parse tree. In other words, apply the node-interesting? predicate to all subtrees of the tree during the traversal, and return the result-transformed list of subtrees. Both the functions node-interesting? and result-transformer are applied on trees and subtrees.
Examples (traverse-and-collect-from-parse-tree resulting-parse-tree (is-tag-of-kind? 'a) parse-tree-to-laml-expression)
See also Scheme source file traverse-and-collect-from-parse-tree

collect-attributes-in-tree
Form (collect-attributes-in-tree tree attr-key)
Description Traverse the parse tree, tree, and return the list all attribute values of the attribute attr-key found in the tree.
Examples (collect-attributes-in-tree tree 'href)
See also Scheme source file collect-attributes-in-tree

is-tag-of-kind?
Form (is-tag-of-kind? tag-kind)
Description Return a predicate which tests whether a subtree or node is of tag-kind (a symbol or string). This function is a useful second parameter to traverse-and-collect-from-parse-tree.
See also Scheme source file is-tag-of-kind?
related function traverse-and-collect-from-parse-tree

parser-status
Form (parser-status)
Description Display parser status in case of error in the parse process.
See also Scheme source file parser-status


6 Top level XML pretty printing functions.

pretty-print-xml-parse-tree-file
Form (pretty-print-xml-parse-tree-file in-file-path [out-file-path])
Description Pretty prints the XML parse tree (Lisp file) in in-file-path. Outputs the pretty printed result in out-file-path, which defaults to in-file-path if not explicitly passed.
See also Scheme source file pretty-print-xml-parse-tree-file
Note For XML-in-LAML ASTs use pretty-render-to-output-port instead of this function

pretty-print-xml-parse-tree
Form (pretty-print-xml-parse-tree parse-tree)
Description Pretty prints a HTML parse tree, and return the result as a string.
See also Scheme source file pretty-print-xml-parse-tree
Note For XML-in-LAML ASTs use pretty-xml-render instead of this function


7 Variables that control the pretty printing.
These variables apply for both HTML and XML.

indentation-delta
Form indentation-delta
Description An integer which gives the level of indentation
See also Scheme source file indentation-delta

use-single-lining
Form use-single-lining
Description A boolean which controls the application of single line pretty printing. If true, the pretty printer will pretty print short list forms on a single line
See also Scheme source file use-single-lining

prefered-maximum-width
Form prefered-maximum-width
Description An integer that expresses the preferred maximum column width
See also Scheme source file prefered-maximum-width


8 Parse tree conversions.
In this section we provide a number of conversion functions that work on parse trees.

parse-tree-to-laml
Form (parse-tree-to-laml tree output-file)
Description Transform an XML or HTML parse tree to a similar surface LAML expression on output-file. This function accept parse tree rooted by the symbols html-tree, xml-tree, as well the symbol tree.
Parameters tree an XML or HTML parse tree
output-file The name of the file on which to write the LAML expression. Can be full path. Must include extension.
See also Scheme source file parse-tree-to-laml
laml.scm function html-to-laml
Note When the resulting file is LAML processed, the LAML file will write the a LAML file, say f.laml, to f.html in the same directory as the laml file.

parse-tree-to-ast
Form (parse-tree-to-ast pt language)
Description Convert a HTML/XML parse tree to a LAML abstract syntax tree in language. The returned LAML abstract syntax tree will have positive spacing (which means that a white space is represented explicitly by the #t value). This function accept parse tree rooted by the symbols html-tree, xml-tree, as well the symbol tree. Recall that the syntax trees are used as the internal format by the validating mirrors of LAML.
Parameters pt The parse tree
language The name of the XML language, such as xhtml10-transitional. A symbol.
See also Scheme source file parse-tree-to-ast
related function parse-tree-to-element-structure

parse-tree-to-element-structure
Form (parse-tree-to-element-structure pt)
Description Convert a HTML/XML parse tree to an element structure ala LENO. This function accept parse tree rooted by the symbols html-tree, xml-tree, as well the symbol tree. Modelled after parse-tree-to-ast.
See also Scheme source file parse-tree-to-element-structure
related function parse-tree-to-ast

Generated: Monday, November 14, 2011, 09:19:50
Generated by LAML SchemeDoc using LAML Version 38.0 (November 14, 2011, full)