Scrawl provides a few reader macros to allow for Scribble-like syntax, if you activative the scrawl:syntax readtable:
CL-USER> (named-readtables:in-readtable scrawl:syntax)
...
CL-USER> '@a[:href "http://google.com"]{g o o g l e}
(A :HREF "http://google.com" "g o o g l e")
We have made an effort to keep the implementation simple (~100 lines total). For a more (complicated, fully-featured) Common Lisp alternative, consider this library.
Scrawl provides an extension to the standard read table which gives special treatment to the @ [ ] { } characters. The general form of a scrawl expression is
'@' <op> <args>? <body>?
where
<op>is any Lisp expression<args>is an optional square-bracketed list, e.g.[1 2 3]<body>is an optional sequence of text, surrounded by braces, e.g.{ foo frob }
Note that the above is sensitive to spaces, so e.g. @foo [1 2 3] is
different from @foo[1 2 3].
The body of a Scrawl expression consists of text, possibly containing further Scrawl expressions. This is read recursively as a sequence of strings and Scrawl expressions. The result of reading
@<op>[<arg1> ... <argN>]{ <body1> ... <bodyM> }
is
(<op> <arg1> ... <argN> <body1> ... <bodyM>)
where <body> contained a total of M text-segments (possibly containing whitespace) and Scrawl expressions.
Here's an extended example:
@div[:id "my-div"]{
@h1{
Hello World!
}
@p{
I am @b{cow}
Hear me moo
I weigh twice as much as you
And I look good on the barbecue
}
}
is read as
(DIV :ID "my-div" (H1 "Hello World!")
(P "I am " (B "cow") "
Hear me moo
I weigh twice as much as you
And I look good on the barbecue"))
There are a few choices we have made.
- Whitespace is trimmed from the start of the first string and the end
of the last, e.g.
@foo{ bar @baz frob }results in(FOO "bar " BAZ " frob") - Whitespace-only strings are ignored, e.g.
@foo{ }results in(FOO). - Escaping within the body of a scrawl expression is accomplished via
@, e.g.@foo{ @"@" }yields(FOO "@") - The easiest way force inclusion of whitespace is to escape it:
@foo{@" "bar}yields'(FOO " " "bar") - Nested braces are fine if they are balanced:
@foo{ { } }yields(FOO "{ }") - Unbalanced braces must be escaped, e.g.
@foo{ @"{" }yields(FOO "{")
For more perspective on what these or other decisions might entail, consider reading Eli Barzilay's The Scribble Reader