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DOC: convert library(sgml) documentation to DocLog format

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Markus Triska
2023-01-24 22:42:58 +01:00
parent 26d39c3617
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src/lib/sgml.pl
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@@ -2,56 +2,69 @@
Predicates for parsing HTML and XML documents. Predicates for parsing HTML and XML documents.
Written 2020-2022 by Markus Triska (triska@metalevel.at) Written 2020-2022 by Markus Triska (triska@metalevel.at)
Part of Scryer Prolog. Part of Scryer Prolog.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
Currently, two predicates are provided: /** Predicates for parsing HTML and XML documents.
- load_html(+Source, -Es, +Options) Currently, two predicates are provided:
- load_xml(+Source, -Es, +Options)
These predicates parse HTML and XML documents, respectively. - `load_html(+Source, -Es, +Options)`
- `load_xml(+Source, -Es, +Options)`
Source must be one of: These predicates parse HTML and XML documents, respectively.
Source must be one of:
- a list of characters with the document contents - a list of characters with the document contents
- stream(S), specifying a stream S from which to read the content - `stream(S)`, specifying a stream S from which to read the content
- file(Name), where Name is a list of characters specifying a file name. - `file(Name)`, where Name is a list of characters specifying a file name.
Es is unified with the abstract syntax tree of the parsed document, Es is unified with the abstract syntax tree of the parsed document,
represented as a list of elements where each is of the form: represented as a list of elements where each is of the form:
* a list of characters, representing text * a list of characters, representing text
* element(Name, Attrs, Children)
- Name, an atom, is the name of the tag
- Attrs is a list of Key=Value pairs:
Key is an atom, and Value is a list of characters
- Children is a list of elements as specified here.
Currently, Options are ignored. In the future, more options may be * `element(Name, Attrs, Children)`
provided to control parsing.
Example: - `Name`, an atom, is the name of the tag
- `Attrs` is a list of `Key=Value` pairs:
`Key` is an atom, and `Value` is a list of characters
- `Children` is a list of elements as specified here.
Currently, Options are ignored. In the future, more options may be
provided to control parsing.
Example:
```
?- load_html("<html><head><title>Hello!</title></head></html>", Es, []). ?- load_html("<html><head><title>Hello!</title></head></html>", Es, []).
```
Yielding: Yielding:
```
Es = [element(html,[], Es = [element(html,[],
[element(head,[], [element(head,[],
[element(title,[], [element(title,[],
["Hello!"])]), ["Hello!"])]),
element(body,[],[])])]. element(body,[],[])])].
```
library(xpath) provides convenient reasoning about parsed documents. `library(xpath)` provides convenient reasoning about parsed documents.
For example, to fetch the title of the document above, we can use: For example, to fetch the title of the document above, we can use:
```
?- load_html("<html><head><title>Hello!</title></head></html>", Es, []), ?- load_html("<html><head><title>Hello!</title></head></html>", Es, []),
xpath(Es, //title(text), T). xpath(Es, //title(text), T).
```
Yielding T = "Hello!". Yielding `T = "Hello!"`.
Use http_open/3 from library(http/http_open) to read answers from Use `http_open/3` from `library(http/http_open)` to read answers from
web servers via streams. web servers via streams.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ */
:- module(sgml, [load_html/3, :- module(sgml, [load_html/3,
load_xml/3]). load_xml/3]).