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reorder and revise dialects section of guide

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Matthew Flatt 2010-05-21 07:16:18 -06:00
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114
collects/scribblings/guide/dialects.scrbl
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@ -26,6 +26,59 @@ new languages.
@; -------------------------------------------------- @; --------------------------------------------------
@section[#:tag "more-hash-lang"]{More Rackets}
``Racket'' is more of an idea about programming languages than a
language in the usual sense. Macros can extend a base language (as
described in @secref["macros"]), and alternate parsers can
construct an entirely new language from the ground up (as described in
@secref["languages"]).
The @hash-lang[] line that starts a Racket module declares the
base language of the module. By ``Racket,'' we usually mean
@hash-lang[] followed by the base language @racketmodname[racket] or
@racketmodname[racket/base] (of which @racketmodname[racket] is an
extension). The Racket distribution provides additional languages,
including the following:
@itemize[
@item{@racketmodname[typed/racket] --- like
@racketmodname[racket], but statically typed; see
@other-manual['(lib "typed-scheme/scribblings/ts-guide.scrbl")]}
@item{@racketmodname[lazy] --- like @racketmodname[racket/base], but
avoids evaluating an expression until its value is needed; see
@other-manual['(lib "lazy/lazy.scrbl")]}
@item{@racketmodname[frtime] --- changes evaluation in an even more
radical way to support reactive programming; see
@other-manual['(lib "frtime/scribblings/frtime.scrbl")]}
@item{@racketmodname[scribble/base] --- a language, which looks more
like Latex than Racket, for writing documentation; see
@other-manual['(lib "scribblings/scribble/scribble.scrbl")]}
]
Each of these languages is used by starting module with the language
name after @hash-lang[]. For example, this source of this
document starts with @racket[@#,hash-lang[] scribble/base].
Furthermore, Racket users can define their own languages, as discussed
in @secref["languages"]. Typically, a language name maps to its
implementation through a module path by adding
@racketidfont{/lang/reader}; for example, the language name
@racketmodname[scribble/base] is expanded to
@racket[scribble/base/lang/reader], which is the module that
implements the surface-syntax parser. Some language names act as
language loaders; for example, @racket[@#,hash-lang[]
@#,racketmodname[planet] _planet-path] downloads, installs, and uses a
language via @seclink["top" #:doc '(lib
"planet/planet.scrbl")]{@|PLaneT|}.
@; --------------------------------------------------
@section[#:tag "standards"]{Standards} @section[#:tag "standards"]{Standards}
Standard dialects of Scheme include the ones defined by @|r5rs| and Standard dialects of Scheme include the ones defined by @|r5rs| and
@ -80,67 +133,6 @@ information about running @|r6rs| programs with Racket.
@; -------------------------------------------------- @; --------------------------------------------------
@section[#:tag "more-hash-lang"]{More Rackets}
Like ``Scheme,'' even ``Racket'' is more of an idea about
programming languages than a language in the usual sense. Macros can
extend a base language (as described in @secref["macros"]), but macros
and alternate parsers can construct an entirely new language from the
ground up.
The @hash-lang[] line that starts a Racket module declares the
base language of the module. By ``Racket,'' we usually mean
@hash-lang[] followed by the base language @racketmodname[racket] or
@racketmodname[racket/base] (of which @racketmodname[racket] is an
extension). The Racket distribution provides additional languages,
including the following:
@itemize[
@item{@racketmodname[typed/racket] --- like
@racketmodname[racket], but statically typed; see
@other-manual['(lib "typed-scheme/scribblings/ts-guide.scrbl")]}
@item{@racketmodname[lazy] --- like @racketmodname[racket/base], but
avoids evaluating an expression until its value is needed; see
@other-manual['(lib "lazy/lazy.scrbl")]}
@item{@racketmodname[frtime] --- changes evaluation in an even more
radical way to support reactive programming; see
@other-manual['(lib "frtime/scribblings/frtime.scrbl")]}
@item{@racketmodname[scribble/base] --- a language, which looks more
like Latex than Racket, for writing documentation; see
@other-manual['(lib "scribblings/scribble/scribble.scrbl")]}
]
Each of these languages is used by starting module with the language
name after @hash-lang[]. For example, this source of this
document starts with @racket[@#,hash-lang[] scribble/base].
Racket users can define their own languages. A language name maps
to its implementation through a module path by adding
@racketidfont{/lang/reader}. For example, the language name
@racketmodname[scribble/doc] is expanded to
@racket[scribble/doc/lang/reader], which is the module that implements
the surface-syntax parser. The parser, in turn, generates a
@racket[module] form, which determines the base language at the level
of syntactic forms an functions.
Some language names act as language loaders. For example,
@racketmodname[s-exp] as a language uses the usual Racket parser
for surface-syntax reading, and then it uses the module path after
@racketmodname[s-exp] for the language's syntactic forms. Thus,
@racket[@#,hash-lang[] @#,racketmodname[s-exp] "mylang.rkt"] parses
the module body using the normal Racket reader, by then imports
the initial syntax and functions for the module body from
@racket["mylang.rkt"]. Similarly, @racket[@#,hash-lang[]
@#,racketmodname[planet] _planet-path] loads a language via
@seclink["top" #:doc '(lib "planet/planet.scrbl")]{@|PLaneT|}.
@; --------------------------------------------------
@section[#:tag "teaching-langs"]{Teaching} @section[#:tag "teaching-langs"]{Teaching}
The @|HtDP| textbook relies on pedagogic variants of Racket that The @|HtDP| textbook relies on pedagogic variants of Racket that