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Fix boundary conditions of diff-indices

This commit is contained in:
Tony Garnock-Jones 2014-12-23 22:00:14 -05:00
parent 480773c23a
commit 29be136d06
1 changed files with 18 additions and 2 deletions
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20
rmacs/diff.rkt
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@ -9,6 +9,7 @@
(require racket/set)
(require racket/match)
(require (only-in racket/sequence sequence-length))
(define (equivalence-classes xs)
(for/fold [(classes (hash))]
@ -55,7 +56,10 @@
'()))))
(define (diff-indices xs ys)
(let loop ((i 0) (j 0) (matches (longest-common-subsequence xs ys)))
(let loop ((i -1)
(j -1)
(matches (append (longest-common-subsequence xs ys)
(list (cons (sequence-length xs) (sequence-length ys))))))
(match matches
['() '()]
[(cons (cons mi mj) rest)
@ -87,4 +91,16 @@
(check-equal? (longest-common-subsequence "abcabba" "cbabac")
'((2 . 0) (3 . 2) (4 . 3) (6 . 4)))
(check-equal? (longest-common-subsequence "cbabac" "abcabba")
'((1 . 1) (2 . 3) (3 . 4) (4 . 6))))
'((1 . 1) (2 . 3) (3 . 4) (4 . 6)))
(check-equal? (longest-common-subsequence
(vector (vector 1 1 1) (vector 1 1 1) (vector 1 1 1) (vector 1 1 1))
(vector (vector 1 1 1) (vector 2 2 2) (vector 1 1 1) (vector 4 4 4)))
'((0 . 0) (1 . 2)))
(check-equal? (diff-indices
(vector (vector 1 1 1) (vector 1 1 1) (vector 1 1 1) (vector 1 1 1))
(vector (vector 1 1 1) (vector 2 2 2) (vector 1 1 1) (vector 4 4 4)))
'((1 0 1 1) (2 2 3 1)))
(check-equal? (longest-common-subsequence '(a b c) '(d e f)) '())
(check-equal? (diff-indices '(a b c) '(d e f)) '((0 3 0 3))))