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Change lens-view*

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This commit is contained in:
Jack Firth 2015-07-08 10:55:06 -07:00
parent 4a05f25f06
commit 62e0073af6
2 changed files with 15 additions and 22 deletions
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28
lens/base/view-set.rkt
View File

@ -10,31 +10,30 @@
(provide
(contract-out [lens-view (-> lens? any/c any/c)]
[lens-view* (->* (any/c) #:rest (listof lens?) any/c)]
[lens-view* (->* (any/c) #:rest (listof lens?) list?)]
[lens-set (-> lens? any/c any/c any/c)]
[lens-set* (->* (any/c) #:rest (listof2 lens? any/c) any/c)]))
(define (lens-view lens v)
(let-lens (view _) lens v
(define (lens-view lens target)
(let-lens (view _) lens target
view))
(define (lens-set lens v x)
(let-lens (_ setter) lens v
(define (lens-set lens target x)
(let-lens (_ setter) lens target
(setter x)))
(define (lens-view* v . lenses)
(for/fold ([v v]) ([lens (in-list lenses)])
(lens-view lens v)))
(define (lens-view* target . lenses)
(map (lens-view _ target) lenses))
(define (lens-set* v . lenses/xs)
(define (lens-set* target . lenses/xs)
(unless (even? (length lenses/xs))
(error 'lens-set*
"expected an even number of association elements\n association elements: ~v"
lenses/xs))
(for/fold ([v v]) ([lens/x (in-slice 2 lenses/xs)])
(for/fold ([target target]) ([lens/x (in-slice 2 lenses/xs)])
(match-define (list lens x) lens/x)
(lens-set lens v x)))
(lens-set lens target x)))
(module+ test
(define (set-first l v)
@ -45,10 +44,9 @@
(define second-lens (make-lens second set-second))
(check-equal? (lens-view first-lens '(1 2 3)) 1)
(check-equal? (lens-set first-lens '(1 2 3) 'a) '(a 2 3))
(check-equal? (lens-view* '((1 2) 3) first-lens second-lens)
2)
(check-equal? (lens-view* '(1 2 3) first-lens second-lens)
'(1 2))
(check-equal? (lens-set* '(1 2 3)
first-lens 10
second-lens 20)
'(10 20 3))
)
'(10 20 3)))

9
lens/base/view-set.scrbl
View File

@ -24,13 +24,8 @@
]}
@defproc[(lens-view* [target target/c] [lens lens?] ...) view/c]{
Like @racket[lens-view], except that it can take multiple lenses,
which are combined into a nested lens. The argument order is
switched, so that the @racket[target] comes first and the
@racket[lens] arguments come after it.
@racket[(lens-view* target lens ...)] produces the same value as
@racket[(lens-view (lens-thrush lens ...) target)], but can be more
efficient.
Like @racket[lens-view], except that it takes multiple lenses and
returns a list of views.
@lenses-examples[
(lens-view* '(a b ((c d) e f) g) third-lens first-lens second-lens)
]}