153 lines
5.5 KiB
Racket
153 lines
5.5 KiB
Racket
#lang scribble/doc
|
|
@require[scribble/manual]
|
|
@require[scribble/eval]
|
|
@require["guide-utils.ss"]
|
|
|
|
@title[#:tag "module-paths"]{Module Paths}
|
|
|
|
A @deftech{module path} is a reference to a module, as used with
|
|
@scheme[require] or as the @scheme[_initial-module-path] in a
|
|
@scheme[module] form. It can be any of several forms:
|
|
|
|
@; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
|
|
@specsubform[#:literals (quote) (#,(scheme quote) id)]{
|
|
|
|
A @tech{module path} that is a quoted identifier refers to a non-file
|
|
@scheme[module] declaration using the identifier. This form of module
|
|
reference makes the most sense in a @tech{REPL}.
|
|
|
|
@examples[
|
|
(module m scheme
|
|
(provide color)
|
|
(define color "blue"))
|
|
(module n scheme
|
|
(require 'm)
|
|
(printf "my favorite color is ~a\n" color))
|
|
(require 'n)
|
|
]}
|
|
|
|
@; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
|
|
@specsubform[id]{
|
|
|
|
A @tech{module path} that is an unquoted identifier refers to an
|
|
installed library. The @scheme[id] is constrained to contain only
|
|
ASCII letters, ASCII numbers, @litchar{+}, @litchar{-}, @litchar{_},
|
|
and @litchar{/}, where @litchar{/} separates path elements within the
|
|
identifier. The elements refer to @tech{collection}s and
|
|
sub-@tech{collections}, instead of directories and sub-directories.
|
|
|
|
An example of this form is @scheme[scheme/date]. It refers to the
|
|
module whose source is the @filepath{date.ss} file in the
|
|
@filepath{scheme} collection, which is installed as part of PLT
|
|
Scheme. The @filepath{.ss} suffix is added automatically.
|
|
|
|
Another example of this form is @scheme[scheme], which is commonly
|
|
used at the initial import. The path @scheme[scheme] is shorthand for
|
|
@scheme[scheme/main]; when the last element of the path has no suffix,
|
|
then @scheme[/main] is automatically added to the end. Thus,
|
|
@scheme[scheme] or @scheme[scheme/main] refers to the module whose
|
|
source is the @filepath{main.ss} file in the @filepath{scheme}
|
|
collection.
|
|
|
|
@examples[
|
|
(module m scheme
|
|
(require scheme/date)
|
|
|
|
(printf "Today is ~s\n"
|
|
(date->string (seconds->date (current-seconds)))))
|
|
(require 'm)
|
|
]}
|
|
|
|
@; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
|
|
@specsubform[rel-string]{
|
|
|
|
A string @tech{module path} is a relative path using Unix-style
|
|
conventions: @litchar{/} is the path separator, @litchar{..} refers to
|
|
the parent directory, and @litchar{.} refers to the same
|
|
directory. The @scheme[rel-string] must not start or end with a path
|
|
separator.
|
|
|
|
The path is relative to the enclosing file, if any, or it is relative
|
|
to the current directory. (More precisely, the path is relative to the
|
|
value of @scheme[(current-load-relative-directory)], which is set
|
|
while loading a file.)
|
|
|
|
@secref["module-basics"] shows examples using relative paths.
|
|
}
|
|
|
|
@; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
|
|
@specsubform[#:literals (lib)
|
|
(lib rel-string)]{
|
|
|
|
Like an unquoted-identifier path, but expressed as a string instead of
|
|
an identifier. Also, the @scheme[rel-string] can end with a file
|
|
suffix, in case the relevant suffix is not @filepath{.ss}.
|
|
|
|
Example of this form include @scheme[(lib "scheme/date.ss")] and
|
|
@scheme[(lib "scheme/date")], which are equivalent to
|
|
@scheme[scheme/date]. Other examples include @scheme[(lib "scheme")],
|
|
@scheme[(lib "scheme/main")], and @scheme[(lib "scheme/main.ss")],
|
|
which are all equivalent to @scheme[scheme].
|
|
|
|
@examples[
|
|
(module m (lib "scheme")
|
|
(require (lib "scheme/date.ss"))
|
|
|
|
(printf "Today is ~s\n"
|
|
(date->string (seconds->date (current-seconds)))))
|
|
(require 'm)
|
|
]}
|
|
|
|
@; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
|
|
@specsubform/subs[#:literals (planet = + -)
|
|
(planet rel-string (user-string pkg-string vers ...))
|
|
([vers nat
|
|
(nat nat)
|
|
(= nat)
|
|
(+ nat)
|
|
(- nat)])]{
|
|
|
|
Accesses a third-party library that is distributed through the
|
|
@|PLaneT| server. A @|PLaneT| reference starts like a @scheme[lib]
|
|
reference, with a relative path, but the path is followed by
|
|
information about the producer, package, and version of the
|
|
library. The specified package is downloaded and installed on demand.
|
|
|
|
The @scheme[vers]es specify a constraint on the acceptable version of
|
|
the package, where a version number is a sequence of non-negative
|
|
integers, and the constraints determine the allowable values for each
|
|
element in the sequence. If no constraint is provided for a particular
|
|
element, then any version is allowed; in particular, omitting all
|
|
@scheme[vers]es means that any version is acceptable. Specifying at
|
|
least one @scheme[vers] is strongly recommended.
|
|
|
|
For a version constraint, a plain @scheme[nat] is the same as
|
|
@scheme[(+ nat)], which matches @scheme[nat] or higher for the
|
|
corresponding element of the version number. A @scheme[(_start-nat
|
|
_end-nat)] matches any number in the range @scheme[_start-nat] to
|
|
@scheme[_end-nat], inclusive. A @scheme[(= nat)] matches only exactly
|
|
@scheme[nat]. A @scheme[(- nat)] matches @scheme[nat] or lower.
|
|
|
|
@examples[
|
|
(eval:alts
|
|
(module m (lib "scheme")
|
|
(require (planet "random.ss" ("schematics" "random.plt" 1 0)))
|
|
(display (random-gaussian)))
|
|
(void))
|
|
(eval:alts
|
|
(require 'm)
|
|
(display 0.9050686838895684))
|
|
]
|
|
}
|
|
|
|
@; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
|
|
@specsubform[#:literals (file)
|
|
(file string)]{
|
|
|
|
Refers to a file, where @scheme[string] is a relative or absolute path
|
|
using the current platform's conventions. This form is not portable,
|
|
and it should @italic{not} be used when a plain, portable
|
|
@scheme[rel-string] suffices.
|
|
|
|
}
|