sml-markup
v1.0.0
Published
A simplistic markup language inspired by XML
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appguruReadme
SML
Small & Simple Markup Language. Similar to XML.
Specification
Context-Free Grammar
The entire syntax (including semantic tokens) is notated in BNF as follows:
Nonterminals: <nonterminal>, terminals: "terminal", productions: <a1> = <b1> + "b2" + ... | ...
<digit> = "1"-"9"
<hex_digit> = <digit> | "a"-"f" | "A"-"F"
<letter> = "a"-"z" | "A"-"Z"
<letter_or_underscore> = <letter> | "_"
<any> = "\u00000" - "\u10FFFF"
<word> = <letter> | <letter> + <word>
<tag_name> = <letter_or_underscore> | <letter_or_underscore> + <tag_name>
<space> = " " | "\t" | "\n"
<spaces> = <space> | <space> + <spaces>
<two_digits> = <hex_digit> + <hex_digit>
<four_digits> = <two_digits> + <two_digits>
<escape_num> = <hex_digit> | <two_digits> | <hex_digit> + <two_digits> | <four_digits> | <hex_digit> + <four_digits> | <two_digits> + <four_digits>
<escape_tex> = <word>
<escape_con> = "#" + <escape_num> | <escape_tex>
<escape_seq> = "&" + <escape_con> + ";"
<opening_tag> = "<" + <tag_name> + ">"
<closing_tag> = "</" + <tag_name> + ">"
<self_enclosing_tag> = "<" + <tag_name> + "/>"
<content> = <any> | <any> + <content>
<tag_con> = <tag> | <content> | <tag_con> <tag_con>
<tag_content> = "" | <spaces> | <spaces> + <tag_con> + <spaces>
<tag_start> = <opening_tag> + <tag_content>
<comment> = "<!--" + <content> + "-->"
<tag> = <tag_start> <closing_tag> | <self_enclosing_tag> | <tag_start> + "</>" | <comment>
<document> = "" | <tag_content>Explanation
SML resembles XML. It is dramatically simplified, however, to the better for some applications.#
There are some differences, though. For example, SML doesn't allow you to have spaces in tags (like <tag >) as there's no need for spaces as there are no attributes.
SML is particularly useful for ASTs (Abstract Syntax Trees) performed by the tokenizer using a CFG (like the one above).
In general, it is a language for noting nested tree hierarchies. Branches of the tree are represented using tags, the root being the document, and you can think of content as "leaves".
Escape sequences are written as codepoint or identifier, with & and ; enclosing the sequence. To escape <, for example, use <.
The content of each tag is trimmed, i.e. spacing is removed at the beginning & the end. " \t\n con tent \n " would become "con tent".
You can force spaces, however, by using escapes - "&20;\t\n con tent \n&20;" would remain the same (but the escapes would be converted).
Regarding indentation: the spaces until the first newline of a tag's content are stored as indentation, and are repeatedly removed after each newline.
Example
An example document
<body>
<!-- No attributes, use tags instead -->
<attribute>value</attribute>
<!-- Syntactic Sugar -->
<attr>value</>
<booleanAttr/>
Some content, spaces are trimmed
Indentation works as well
<body>Object Notation
Similar to Luon, SML can be used for representing any object.
- Atomics: Self-enclosing tags: the booleans
<true/>and<false/>as well as<nil\>(bothnull&undefined) - Numbers:
<number>tag with decimal representation as content - Text: Implicit (
textwould be"text"), buttexttag can be used - Lists:
<list>tag containing all elements - Sets:
<set>tag containing all elements - Objects:
<dictionairy>tag with<entry>key<value>value</value></entry>entries - Maps: Same as objects, however using the
<map>tag
API
Note that the architecture of SML resembles Luon.
Versions
- 1.0.0
- Initial release
Installation
Install the NPM package sml-markup:
npm install s-m-lThe API supports various levels of restrictions, and thus many functions are configurable.
Import
const sml=require("sml-markup");DOM
The document object model is quite simple in SML.
Every tag is an Element in SML - even the root element, the document, is one.
Element
name: tag name,undefinedfor theDocumentelement.content: array of element content,undefinedfor self enclosing tags
Document
Extends Element, but has no name.
Element Builders
ElementBuilder
The base element builder which helps you create a DOM by having a pointer to the current open tag and allowing operations like auto closing, opening, appending etc. All ElementBuilders can be accessed using the following lookup, or NameInCamelCase + ElementBuilder (for example StrictSearchingElementBuilder).
element_builders
Various inheriting classes, which only differ in the way they handle closing tags by name.
forcing
Always closes the current open tag.
strict
Will throw an error if the current active tag has a different name.
ignoring
Silently ignores that the current open tag can not be closed.
searching
Searches for a matching tag and closes the top tag if none is found.
strict_searching
Searches for a matching tag and if none is found, throws an error.
forcing_searching
Searches for a matching tag and if none is found, closes the current tag.
ignore_searching
Searches for a matching tag and closes it. Silently fails.
Reading
Operates on streams, just like Luon.
reader(config)
Creates a reader with a read(input_stream) function which returns a SML DOM.
config can either be an object with configuration options, or a name to look up from the predefined readers.
Examples:
const html_escape_reader = sml.reader({escape_set: "html"});
const default_reader = sml.reader();
const strict = sml.reader("strict");
const ignoring = sml.reader("ignoring");readStrict
Shorthand for sml.reader("strict").read
readIgnore
Shorthand for sml.reader("ignore").read
objectReader(config)
Creates an object reader with a read(dom) function which returns a JS object.
config can either be an object with configuration options, or a name to look up from the predefined readers.
readObject(dom)
Shorthand for sml.objectReader().read
Writing
Operates on streams as well, just like Luon.
writer(config)
Creates a writer with a write(output_stream) function which returns a SML DOM.
config can either be an object with configuration options, or a name to look up from the predefined readers.
Examples:
const html_escape_writer = sml.writer({escape_set: "html"});
const default_reader = sml.writer();
const compressing = sml.writer("compress");
const beautifying = sml.writer("beautify");objectWriter(config)
Creates an object writer with a write(object) function which returns a SML DOM representing the object.
config can either be an object with configuration options, or a name to look up from the predefined readers.
writeObject(dom)
Shorthand for sml.objectWriter().read
writeObjectStrict(dom)
Shorthand for sml.objectWriter("strict").read
Recommendations
Do not confuse SML and XML; they are similar, but SML is not fully compatible with XML.