4.3.1 Typesetting Code

The codeblock and code forms (see #lang-Specified Code) typeset code verbatim, adding a layer of color to the code based on the same syntax-coloring parsers that are used by DrRacket. Input that is parsed as an identifier is further given a lexical context and hyperlinked via for-label imports.

The racketblock and racket forms (see Racket Code) typeset S-expression code roughly verbatim, but roughly by quoting the source term with syntax. Identifiers in the quoted S-expression are hyperlinked via for-label imports.

The two different approaches to typesetting code—codeblock and code versus racketbock and racket—have different advantages and disadvantages:

• The codeblock and code forms work with non-S-expression syntax, and they give authors more control over output (e.g., the literal number 2/4 is not normalized to 1/2). The codeblock and code forms do not yet support escapes to Scribble element mode, and they cannot adapt spacing based on the width of elements in escapes.

• The racketblock and racket forms are more efficient and allow escapes to Scribble element mode. The racketblock and racket forms are tied to S-expression syntax, however, and they are based on a syntax representation that tends to normalize source terms (e.g., the literal number 2/4 is normalized to 1/2).

4.3.1.1 #lang-Specified Code

The str-exprs should normally start with #lang to determine the reader syntax for the module, but the resulting “module” need not expand or compile—except as needed by expand-expr. If expand-expr is omitted or produces false, then the input formed by str-expr is read until an end-of-file is encountered, otherwise a single form is read from the input.

When keep-expr produces a true value (the default), the first line in the input (which is typically #lang) is preserved in the typeset output, otherwise the first line is dropped. The typeset code is indented by the amount specified by indent-expr, which defaults to 0.

When expand-expr produces #f (which is the default), identifiers in the typeset code are colored and linked based on for-label bindings in the lexical environment of the syntax object provided by context-expr. The default context-expr has the same lexical context as the first str-expr. When line-number-expr is true, line number is enabled starting from line-number-expr.

When expand-expr produces a procedure, it is used to macro-expand the parsed program, and syntax coloring is based on the parsed program.

For example,

@codeblock|{

#lang scribble/manual

@codeblock{

#lang scribble/manual

@title{Hello}

}

}|

produces the typeset result

#lang scribble/manual

@codeblock{

#lang scribble/manual

@title{Hello}

}

For example,

This is @code[#:lang "at-exp racket"]|{@bold{Hi}}|'s result:

@bold{Hi}.

produces the typeset result

This is @bold{Hi}’s result: Hi.

4.3.1.2 Racket Code

(racketblock

(define (loop x)

(loop (not x))))

produces the output

(define (loop x)

(loop (not x)))

with the (loop (not x)) indented under define, because that’s the way it is idented the use of racketblock. Source-location span information is used to preserve #true versus #t and #false versus #f, and syntax-object properties are used to preserve square brackets and curly braces versus parentheses; otherwise, using syntax objects tends to normalize the form of S-expression elements.

In the above example, define is typeset as a keyword (in black) and as a hyperlink to define’s definition in the reference manual, because this document was built using a for-label binding of define (in the source) that matches a definition in the reference manual. Similarly, not is a hyperlink to its definition in the reference manual.

Like other forms defined via define-code, racketblock expands identifiers that are bound as element transformers.

An #:escape clause specifies an identifier to escape back to an expression that produces produces an element. But default, the escape identifier is unsyntax. For example,

(racketblock

(+ 1 #,(elem (racket x) (subscript "2"))))

produces

(+ 1 x2)

The escape-id that defaults to unsyntax is regonized via free-identifier=?, so a binding can hide the escape behavior:

(racketblock

(let ([unsyntax #f])

(racketblock

#'(+ 1 #,x))))

The RACKETBLOCK form’s default escape is UNSYNTAX instead of unsyntax.

A few other escapes are recognized symbolically:

• (code:line datum ...) typesets as the sequence of datums (i.e., without the code:line wrapper).

• (code:comment datum) typesets like datum, but colored as a comment and prefixed with a semi-colon. A typical datum escapes from Racket-typesetting mode using unsyntax and produces a paragraph using t:

  (code:comment @#,t{this is a comment})

  (Note that @#,foo{...} reads as #,(foo "...").)

• typesets as a blank space.

• (code:hilite datum) typesets like datum, but with a background highlight.

• (code:quote datum) typesets like (quote datum), but without rendering the quote as '.

• _id typesets as id, but colored as a variable (like racketvarfont); this escape applies only if _id has no for-label binding and is not specifically colored as a subform non-terminal via defform, a variable via defproc, etc.

See also scribble/comment-reader.

The source location of lang (relative to the body datums) determines the relative positioning of the #lang line in the typeset output. So, line up lang with the left end of the content code.

If #:file is provided, then the code block is typeset using filebox with filename-expr as the filename argument.

4.3.1.3 Preserving Comments

#reader scribble/comment-reader

As a reader module, scribble/comment-reader reads a single S-expression that contains ;-based comment lines, and it wraps the comments with code:comment for use with forms like racketblock. More precisely, scribble/comment-reader extends the current reader to adjust the parsing of ;.

For example, within a Scribble document that imports scribble/manual,

@#reader scribble/comment-reader

(racketblock

;; This is not a pipe

(make-pipe)

)

generates

; This is not a pipe

(make-pipe)

The initial @ is needed above to shift into S-expression mode, so that #reader is recognized as a reader declaration instead of literal text. Also, the example uses (racketblock ....) instead of @racketblock[....] because the @-reader would drop comments within the racketblock before giving scribble/comment-reader a chance to convert them.

4.3.1.4 Code Fonts and Styles