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#lang racket/base | ||
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(require lens/base/main | ||
racket/contract/base | ||
racket/list | ||
racket/set | ||
fancy-app | ||
) | ||
(module+ test | ||
(require rackunit)) | ||
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(define (filterer-lens pred) | ||
(make-lens | ||
(filter pred _) | ||
(λ (tgt nvw) | ||
(unless (andmap pred nvw) | ||
(error 'filterer-lens "expected (listof ~a), given: ~v" (contract-name pred) nvw)) | ||
(append nvw (filter-not pred tgt))))) | ||
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(define (set-filterer-lens pred) | ||
(make-lens | ||
(set-filter pred _) | ||
(λ (tgt nvw) | ||
(unless (andmap pred (set->list nvw)) | ||
(error 'set-filterer-lens "expected (set/c ~a), given: ~v" (contract-name pred) nvw)) | ||
(set-union (set-filter-not pred tgt) nvw)))) | ||
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(define (set-filter pred set) | ||
(for/fold ([set set]) ([elem (in-set set)] #:unless (pred elem)) | ||
(set-remove set elem))) | ||
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(define (set-filter-not pred set) | ||
(for/fold ([set set]) ([elem (in-set set)] #:when (pred elem)) | ||
(set-remove set elem))) | ||
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(module+ test | ||
(check-equal? (lens-view (filterer-lens number?) '(1 a 2 b c 3 d e)) | ||
'(1 2 3)) | ||
(check-equal? (lens-set (filterer-lens number?) '(1 a 2 b c 3 d e) '(4 5 6 7)) | ||
'(4 5 6 7 a b c d e)) | ||
(check-equal? (lens-view (set-filterer-lens number?) (set 1 'a 2 'b 'c 3 'd 'e)) | ||
(set 1 2 3)) | ||
(check-equal? (lens-set (set-filterer-lens number?) (set 1 'a 2 'b 'c 3 'd 'e) (set 4 5 6 7)) | ||
(set 4 5 6 7 'a 'b 'c 'd 'e)) | ||
) |