racket/collects/unstable/scribblings/list.scrbl
Sam Tobin-Hochstadt 7c9d1b47cf fix docs typo
svn: r17539
2010-01-07 19:10:27 +00:00

82 lines
2.4 KiB
Racket

#lang scribble/doc
@(require scribble/base
scribble/manual
scribble/eval
"utils.ss"
(for-label scheme/dict
unstable/list
syntax/id-table
scheme/contract
scheme/base))
@(define the-eval (make-base-eval))
@(the-eval '(require unstable/list))
@title[#:tag "list"]{Lists}
@defmodule[unstable/list]
@unstable-header[]
@defproc[(list-prefix? [l list?]
[r list?])
boolean?]{
True if @scheme[l] is a prefix of @scheme[r].
@examples[#:eval the-eval
(list-prefix? '(1 2) '(1 2 3 4 5))
]
}
@addition{Sam Tobin-Hochstadt}
@defproc[(filter-multiple [l list?] [f procedure?] ...) (values list? ...)]{
Produces @scheme[(values (filter f l) ...)].
@examples[#:eval the-eval
(filter-multiple (list 1 2 3 4 5) even? odd?)
]
}
@defproc[(extend [l1 list?] [l2 list?] [v any/c]) list?]{
Extends @scheme[l2] to be as long as @scheme[l1] by adding @scheme[(-
(length l1) (length l2))] copies of @scheme[v] to the end of
@scheme[l2].
@examples[#:eval the-eval
(extend '(1 2 3) '(a) 'b)
]}
@addition{Ryan Culpepper}
@defproc[(check-duplicate [lst list?]
[#:key extract-key (-> any/c any/c) (lambda (x) x)]
[#:same? same?
(or/c (any/c any/c . -> . any/c)
dict?)
equal?])
(or/c any/c #f)]{
Returns the first duplicate item in @scheme[lst]. More precisely, it
returns the first @scheme[_x] such that there was a previous
@scheme[_y] where @scheme[(same? (extract-key _x) (extract-key _y))].
The @scheme[same?] argument can either be an equivalence predicate
such as @scheme[equal?] or @scheme[eqv?] or a dictionary. In the
latter case, the elements of the list are mapped to @scheme[#t] in the
dictionary until an element is discovered that is already mapped to a
true value. The procedures @scheme[equal?], @scheme[eqv?], and
@scheme[eq?] automatically use a dictionary for speed.
@(the-eval '(require syntax/id-table scheme/dict))
@examples[#:eval the-eval
(check-duplicate '(1 2 3 4))
(check-duplicate '(1 2 3 2 1))
(check-duplicate '((a 1) (b 2) (a 3)) #:key car)
(define id-t (make-free-id-table))
(check-duplicate (syntax->list #'(a b c d a b))
#:same? id-t)
(dict-map id-t list)
]
}