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Fix discussion of filter.

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Closes PR 15083.
This commit is contained in:
Vincent St-Amour 2016-01-01 12:44:12 -06:00
parent 110f1bd9b0
commit 4c04d4afce
1 changed files with 9 additions and 9 deletions
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18
pkgs/racket-doc/scribblings/guide/lists.scrbl
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@ -74,15 +74,7 @@ by @racket[and]ing or @racket[or]ing:
(ormap number? (list "a" "b" 6)) (ormap number? (list "a" "b" 6))
] ]
The @racket[filter] function keeps elements for which the body result The @racket[map], @racket[andmap], and @racket[ormap]
is true, and discards elements for which it is @racket[#f]:
@interaction[
(filter string? (list "a" "b" 6))
(filter positive? (list 1 -2 6 7 0))
]
The @racket[map], @racket[andmap], @racket[ormap], and @racket[filter]
functions can all handle multiple lists, instead of just a single functions can all handle multiple lists, instead of just a single
list. The lists must all have the same length, and the given function list. The lists must all have the same length, and the given function
must accept one argument for each list: must accept one argument for each list:
@ -93,6 +85,14 @@ must accept one argument for each list:
(list 6 3 7)) (list 6 3 7))
] ]
The @racket[filter] function keeps elements for which the body result
is true, and discards elements for which it is @racket[#f]:
@interaction[
(filter string? (list "a" "b" 6))
(filter positive? (list 1 -2 6 7 0))
]
The @racket[foldl] function generalizes some iteration functions. It The @racket[foldl] function generalizes some iteration functions. It
uses the per-element function to both process an element and combine uses the per-element function to both process an element and combine
it with the ``current'' value, so the per-element function takes an it with the ``current'' value, so the per-element function takes an