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September 2017 Update

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Ingy döt Net 2017-09-23 10:01:46 +02:00
parent bba7bfd280
commit ba8067c3b7
14570 changed files with 153136 additions and 63871 deletions
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30
Task/Symmetric-difference/Scheme/symmetric-difference-1.ss Normal file
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(import (scheme base)
(scheme write))
;; -- given two sets represented as lists, return (A \ B)
(define (a-without-b a b)
(cond ((null? a)
'())
((member (car a) (cdr a)) ; drop head of a if it's a duplicate
(a-without-b (cdr a) b))
((member (car a) b) ; head of a is in b so drop it
(a-without-b (cdr a) b))
(else ; head of a not in b, so keep it
(cons (car a) (a-without-b (cdr a) b)))))
;; -- given two sets represented as lists, return symmetric difference
(define (symmetric-difference a b)
(append (a-without-b a b)
(a-without-b b a)))
;; -- test case
(define A '(John Bob Mary Serena))
(define B '(Jim Mary John Bob))
(display "A\\B: ") (display (a-without-b A B)) (newline)
(display "B\\A: ") (display (a-without-b B A)) (newline)
(display "Symmetric difference: ") (display (symmetric-difference A B)) (newline)
;; -- extra test as we are using lists
(display "Symmetric difference 2: ")
(display (symmetric-difference '(John Serena Bob Mary Serena)
'(Jim Mary John Jim Bob))) (newline)

25
Task/Symmetric-difference/Scheme/symmetric-difference-2.ss Normal file
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(import (scheme base)
(scheme write)
(srfi 1))
(define (a-without-b a b)
(lset-difference equal?
(delete-duplicates a)
(delete-duplicates b)))
(define (symmetric-difference a b)
(lset-xor equal?
(delete-duplicates a)
(delete-duplicates b)))
;; -- test case
(define A '(John Bob Mary Serena))
(define B '(Jim Mary John Bob))
(display "A\\B: ") (display (a-without-b A B)) (newline)
(display "B\\A: ") (display (a-without-b B A)) (newline)
(display "Symmetric difference: ") (display (symmetric-difference A B)) (newline)
;; -- extra test as we are using lists
(display "Symmetric difference 2: ")
(display (symmetric-difference '(John Serena Bob Mary Serena)
'(Jim Mary John Jim Bob))) (newline)