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add add-lens, subtract-lens, and modulo-lens #289

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add add-lens, subtract-lens, and modulo-lens #289

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82 changes: 82 additions & 0 deletions lens-data/lens/private/number/number.rkt
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Original file line number Diff line number Diff line change
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#lang sweet-exp racket/base

provide add-lens
subtract-lens
modulo-lens

require fancy-app
lens/common
lens/private/isomorphism/base
module+ test
require rackunit

(define (add-lens x)
(make-isomorphism-lens
(+ _ x)
(- _ x)))

(define (subtract-lens x)
(make-isomorphism-lens
(- _ x)
(+ _ x)))

(define (modulo-lens n)
;; a = n*q + r
(make-lens
(modulo _ n)
(λ (a r*)
(define r (modulo a n))
(define q (/ (- a r) n))
(+ (* n q) r*))))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(module+ test
(check-equal? (lens-view (add-lens 5) 3) 8)
(check-equal? (lens-set (add-lens 5) 3 8) 3)
(check-equal? (lens-set (add-lens 5) 3 27) 22)

(check-equal? (lens-view (subtract-lens 5) 3) -2)
(check-equal? (lens-set (subtract-lens 5) 3 -2) 3)
(check-equal? (lens-set (subtract-lens 5) 3 17) 22)

(define mod2 (modulo-lens 2))
(define mod10 (modulo-lens 10))

(check-equal? (lens-view mod2 0) 0)
(check-equal? (lens-view mod2 1) 1)
(check-equal? (lens-view mod2 2) 0)
(check-equal? (lens-view mod2 3) 1)
(check-equal? (lens-view mod2 10) 0)
(check-equal? (lens-view mod2 11) 1)
(check-equal? (lens-set mod2 0 0) 0)
(check-equal? (lens-set mod2 0 1) 1)
(check-equal? (lens-set mod2 1 0) 0)
(check-equal? (lens-set mod2 1 1) 1)
(check-equal? (lens-set mod2 2 0) 2)
(check-equal? (lens-set mod2 2 1) 3)
(check-equal? (lens-set mod2 3 0) 2)
(check-equal? (lens-set mod2 3 1) 3)
(check-equal? (lens-set mod2 10 0) 10)
(check-equal? (lens-set mod2 10 1) 11)
(check-equal? (lens-set mod2 11 0) 10)
(check-equal? (lens-set mod2 11 1) 11)

(check-equal? (lens-view mod10 0) 0)
(check-equal? (lens-view mod10 1) 1)
(check-equal? (lens-view mod10 2) 2)
(check-equal? (lens-view mod10 9) 9)
(check-equal? (lens-view mod10 10) 0)
(check-equal? (lens-view mod10 11) 1)
(check-equal? (lens-view mod10 19) 9)
(check-equal? (lens-view mod10 20) 0)
(check-equal? (lens-set mod10 0 0) 0)
(check-equal? (lens-set mod10 0 4) 4)
(check-equal? (lens-set mod10 8 0) 0)
(check-equal? (lens-set mod10 8 4) 4)
(check-equal? (lens-set mod10 11 0) 10)
(check-equal? (lens-set mod10 11 4) 14)
(check-equal? (lens-set mod10 25 0) 20)
(check-equal? (lens-set mod10 25 9) 29)
)