Parser Expansions¶

Warning

This is a highly experimental extension. It is not well specified, is not supported by any of the editor integrations or syntax highlighters, and may change or disappear in the future.

The syntax:

#:<name>:<text>

gets transformed, setter-like, into:

<name>-parser(<text>)

The <text> part can be either delimited or undelimited. Undelimited text can contain anything but commas, semicolons, brackets of any kind, and whitespace. All the following are valid:

#:https://opendylan.org/
#:time:12:30am
#:date:12/3/2000
#:file:D:\dylan\sources\
#:mailto:dylan-lang@googlegroups.com

In the delimited form, you have a choice of delimiters: "...", (...), [...], {...}, |...|, `...`, '...'. Within the delimiters, only the matching close delimiter must be escaped. The selection allows you to choose the delimiter requiring least escaping for the enclosed data. The text (less the delimiters) is passed to the parsing function. Examples:

#:file:"C:\Program Files\Open Dylan\."
#:html:{<html>
  <head><title>Foo</title></head>
  <body bgcolor="#FFFFFF">
  </body>
  </html>}

An example parser:

define method html-parser
    (text :: <byte-string>)
 => (doc :: <html-document>)
   make(<html-document>, text: text)
end method;

If an appropriate function isn’t defined, you get a standard unbound variable reference message indicating the # literal.

Note that there is no escape processing except that the end delimiter may be escaped with a backslash and the escape character itself is not removed. For example, #:file:"C:\foo\" is an error because the end delimiter is escaped and therefore the hash literal is unterminated. #:file:"C:\foo\"" results in the literal string C:\foo\" being passed to the parser.