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fix #<undefined> mention and adjust example to always terminate

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Robby Findler 2014-05-04 20:53:09 -05:00
parent 9613d45566
commit 1ce09cf924
2 changed files with 19 additions and 12 deletions
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2
pkgs/racket-pkgs/racket-doc/scribblings/guide/define.scrbl
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@ -237,7 +237,7 @@ Internal definitions in a particular @racket[_body] sequence are
mutually recursive; that is, any definition can refer to any other mutually recursive; that is, any definition can refer to any other
definition---as long as the reference isn't actually evaluated before definition---as long as the reference isn't actually evaluated before
its definition takes place. If a definition is referenced too early, its definition takes place. If a definition is referenced too early,
the result is a special value @|undefined-const|. an error occurs.
@defexamples[ @defexamples[
(define (weird) (define (weird)

29
pkgs/racket-pkgs/racket-doc/scribblings/guide/let.scrbl
View File

@ -129,26 +129,33 @@ The @racket[_expr]s in a @racket[letrec] form are most often
] ]
@interaction[ @interaction[
(letrec ([tarzan-in-tree? (letrec ([tarzan-near-top-of-tree?
(lambda (name path) (lambda (name path depth)
(or (equal? name "tarzan") (or (equal? name "tarzan")
(and (directory-exists? path) (and (directory-exists? path)
(tarzan-in-directory? path))))] (tarzan-in-directory? path depth))))]
[tarzan-in-directory? [tarzan-in-directory?
(lambda (dir) (lambda (dir depth)
(ormap (lambda (elem) (cond
(tarzan-in-tree? (path-element->string elem) [(zero? depth) #f]
(build-path dir elem))) [else
(directory-list dir)))]) (ormap
(tarzan-in-tree? "tmp" (find-system-path 'temp-dir))) (λ (elem)
(tarzan-near-top-of-tree? (path-element->string elem)
(build-path dir elem)
(- depth 1)))
(directory-list dir))]))])
(tarzan-near-top-of-tree? "tmp"
(find-system-path 'temp-dir)
4))
] ]
While the @racket[_expr]s of a @racket[letrec] form are typically While the @racket[_expr]s of a @racket[letrec] form are typically
@racket[lambda] expressions, they can be any expression. The @racket[lambda] expressions, they can be any expression. The
expressions are evaluated in order, and after each value is obtained, expressions are evaluated in order, and after each value is obtained,
it is immediately associated with its corresponding @racket[_id]. If it is immediately associated with its corresponding @racket[_id]. If
an @racket[_id] is referenced before its value is ready, the result is an @racket[_id] is referenced before its value is ready, an
@|undefined-const|, just as for internal definitions. error is raised, just as for internal definitions.
@interaction[ @interaction[
(letrec ([quicksand quicksand]) (letrec ([quicksand quicksand])