67 lines
2.0 KiB
Racket
67 lines
2.0 KiB
Racket
#lang scribble/doc
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@(require scribble/manual
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scribble/eval
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"guide-utils.ss")
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@title[#:tag "module-basics"]{Module Basics}
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The space of module names is distinct from the space of normal Scheme
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definitions. Indeed, since modules typically reside in files, the
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space of module names is explicitly tied to the filesystem at run
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time. For example, if the file @filepath{/home/molly/cake.ss} contains
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@schememod[
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scheme
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(provide print-cake)
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(code:comment #, @t{draws a cake with @scheme[n] candles})
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(define (print-cake n)
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(printf " ~a \n" (make-string n #\.))
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(printf " .-~a-.\n" (make-string n #\|))
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(printf " | ~a |\n" (make-string n #\space))
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(printf "---~a---\n" (make-string n #\-)))
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]
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then it can be used as the source of a module whose full name is based
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on the path @filepath{/home/molly/cake.ss}. The @scheme[provide] line
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exports the definition @scheme[print-cake] so that it can be used
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outside the module.
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Instead of using its full path, a module is more likely to be
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referenced by a relative path. For example, a file
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@filepath{/home/molly/random-cake.ss} could use the @filepath{cake.ss} module
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like this:
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@schememod[
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scheme
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(require "cake.ss")
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(print-cake (random 30))
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]
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The relative reference @scheme["cake.ss"] in the import
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@scheme[(require "cake.ss")] works because the @filepath{cake.ss} module
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source is in the same directory as the @filepath{random-cake.ss}
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file. (Unix-style relative paths are used for relative module
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references on all platforms, much like relative URLs.)
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Library modules that are distributed with PLT Scheme are usually
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referenced through an unquoted, suffixless path. The path is relative
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(roughly) to the library installation directory. The module below
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refers to the @filepath{date.ss} library that is part of the
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@filepath{scheme} collection.
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@schememod[
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scheme
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(require scheme/date)
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(printf "Today is ~s\n"
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(date->string (seconds->date (current-seconds))))
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]
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We discuss more forms of module reference later in
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@secref["module-paths"].
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