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;; -*- compile-command: "guile -L . huffman-test.scm"; -*-
(use-modules (srfi srfi-64)
(pq)
(huffman))
(define runner "a fast runner need never be afraid of the dark")
(define runner-opt-key '((#\v . "111001") (#\u . "111000") (#\t . "0100") (#\s . "111011") (#\r . "100") (#\o . "111010") (#\n . "1111") (#\k . "101101") (#\i . "101100") (#\h . "101111") (#\f . "1010") (#\e . "110") (#\d . "0101") (#\b . "101110") (#\a . "011") (#\space . "00")))
(define abcde "A_DEAD_DAD_CEDED_A_BAD_BABE_A_BEADED_ABACA_BED")
(define abcde-opt-key '((#\_ . "01") (#\E . "110") (#\D . "00") (#\C . "1110") (#\B . "1111") (#\A . "10")))
(define abcde-encoded "1001001101000010010000111101100011000011001111110000111111011111100110011111110100011000011011111011101001111111000")
(define (hash-table->alist ht)
(hash-map->list cons ht))
(define (node-pq->char-alist pq)
(map (lambda (ele)
(cons (node-char (car ele))
(cdr ele)))
(car pq)))
(define (extract-tree pq)
(car (pq-front pq)))
(test-begin "harness")
(test-equal "hash-frequency zero chars, empty hash"
'()
(sort-rao (hash-table->alist (hash-frequency ""))))
(test-equal "hash-frequency single 'c' key pair correct"
'((#\c . 1))
(sort-rao (hash-table->alist (hash-frequency "c"))))
(test-equal "hash-frequency double 'c' key pair correct"
'((#\c . 2))
(sort-rao (hash-table->alist (hash-frequency "cc"))))
(test-equal "hash-frequency couple letters key pair correct"
'((#\c . 2) (#\Y . 1))
(sort-rao (hash-table->alist (hash-frequency "cYc"))))
(test-equal "hash-frequency couple letters key pair correct"
'((#\c . 2) (#\Y . 1))
(sort-rao (hash-table->alist (hash-frequency "cYc"))))
(test-equal "hash-frequency abcde"
'((#\_ . 10) (#\E . 7) (#\D . 10) (#\C . 2) (#\B . 6) (#\A . 11))
(sort-rao (hash-table->alist (hash-frequency abcde))))
(test-assert "frequencies->pq accepts hashtable and returns a pq"
(pq? (frequencies->pq (make-hash-table))))
(test-equal "frequencies->pq single entry"
'((#\a . -3))
(node-pq->char-alist (frequencies->pq (hash-frequency "aaa"))))
(test-equal "frequencies->pq double entry"
'((#\a . -3) (#\b . -3))
(node-pq->char-alist (frequencies->pq (hash-frequency "aaabbb"))))
(test-equal "frequencies->pq tie natural order"
'((#\a . -3) (#\b . -3) (#\c . -4))
(node-pq->char-alist (frequencies->pq (hash-frequency "cabababccc"))))
(test-equal "frequencies->pq tie reverse order"
'((#\a . -3) (#\b . -3) (#\c . -4))
(node-pq->char-alist (frequencies->pq (hash-frequency "cbababaccc"))))
(test-equal "frequencies->pq abcde"
'((#\C . -2) (#\B . -6) (#\E . -7) (#\D . -10) (#\_ . -10) (#\A . -11))
(node-pq->char-alist (frequencies->pq (hash-frequency abcde))))
(let* ((pq (frequencies->pq (hash-frequency "aab")))
(pqo (frequencies->pq (hash-frequency "aab")))
(lc (car (pq-front pq)))
(rc (car (pq-rear pq)))
(p (begin (combine-and-reinsert! pq)
(car (pq-front pq)))))
(test-assert "pq and pqo now different objects, but both pqs"
(and (not (equal? pq pqo))
(pq? pq)
(pq? pqo)))
(test-assert "combine-and-reinsert! left child is correct"
(equal? (node-left p) lc))
(test-assert "combine-and-reinsert! right child is correct"
(equal? (node-right p) rc))
(test-equal "combine-and-reinsert! correctly sums priority"
-3
(cdr (pq-front pq))))
(let* ((pq (frequencies->pq (hash-frequency "aaabbbcccc"))))
(combine-and-reinsert! pq)
(test-equal "combine-and-reinsert! first elements combined"
#\c
(node-char (car (pq-front pq))))
(test-equal "combine-and-reinsert! new node inserted in correct spot"
-6
(cdr (pq-rear pq))))
(let ((pq (combine-all! (frequencies->pq (hash-frequency runner)))))
(test-assert "combine-all! returns a pq"
(pq? pq))
(test-equal "combine-all! pq is of length one"
1
(pq-length pq))
(test-assert "combine-all! root item is a node"
(node? (car (pq-front pq))))
(test-equal "combine-all! root frequency matches length of str"
-46
(cdr (pq-front pq))))
(test-equal "create-encodings level-1 tree"
'((#\a . "0"))
(sort-rao (create-encodings (extract-tree
(combine-all!
(frequencies->pq
(hash-frequency "a")))))))
;;;; note: verified manually: https://en.wikipedia.org/wiki/Huffman_coding
(test-equal "create-encodings abcde"
abcde-opt-key
(sort-rao (create-encodings (extract-tree
(combine-all!
(frequencies->pq
(hash-frequency abcde)))))))
(test-equal "create-encodings runner"
runner-opt-key
(sort-rao (create-encodings (extract-tree
(combine-all!
(frequencies->pq
(hash-frequency runner)))))))
(let ((none (encode-text "")))
(test-assert "encode-text nothing empty string"
(string-null? (car none)))
(test-assert "encode-text nothing empty alist"
(null? (cdr none))))
(let ((limit (encode-text abcde)))
(test-equal "encode-text abcde string"
abcde-encoded
(car limit))
(test-equal "encode-text abcde alist"
abcde-opt-key
(sort-rao (cdr limit))))
(test-equal "decode single char"
"x"
(decode-text "00011" '((#\x . "00011") (#\y . "001"))))
(test-equal "decode two chars"
"xq"
(decode-text "00011" '((#\x . "000") (#\y . "011") (#\q . "11"))))
(test-equal "decode abcde"
abcde
(decode-text abcde-encoded abcde-opt-key))
(test-error "decode abcde nonsense key"
#t
(decode-text abcde-encoded runner-opt-key))
(test-end "harness")
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