learning-sicp

commit 11a5759d3ad293cc2e38127888edf5d1e2db503e
parent 660a9ffb718ce541994fb28d2949350d0a1ae952
Author: Yuval Langer <yuval.langer@gmail.com>
Date:   Mon, 27 Mar 2023 14:01:08 +0300

Add some chapter 2.3 Symbolic Data solutions and tests.

Diffstat:
M
solutions/huffman-codes-stuff.scm
 | 
24
+++++++++++++++---------
M
solutions/tests/exercise-2.67-tests.scm
 | 
3
+++
M
solutions/tests/exercise-2.69-tests.scm
 | 
17
+++++++++++++++++

3 files changed, 35 insertions(+), 9 deletions(-)
diff --git a/solutions/huffman-codes-stuff.scm b/solutions/huffman-codes-stuff.scm
@@ -1,7 +1,12 @@
 (define-library (huffman-codes-stuff)
   (import (scheme base))
   (import (scheme cxr))
-  
+  (export make-code-tree
+          make-leaf
+          sample-message
+          sample-tree
+          generate-huffman-tree)
+
   (begin
     (define (make-leaf symbol weight)
       (list 'leaf symbol weight))
@@ -58,7 +63,7 @@
       (cond
        ((null? set) (list x))
        ((< (weight x)
-           (car set))
+           (weight (car set)))
         (cons x set))
        (else (cons (car set)
                    (adjoin-set x
@@ -74,7 +79,7 @@
              (make-leaf-set (cdr pairs))))))
 
     ;; Exercise 2.67
-    
+
     (define sample-tree
       (make-code-tree
        (make-leaf 'A 4)
@@ -86,7 +91,7 @@
 
     (define sample-message
       '(0 1 1 0 0 1 0 1 0 1 1 1 0))
-    
+
 
     ;; Exercise 2.68
 
@@ -109,7 +114,7 @@
           (encode-symbol' (cons 1 bits)
                           (right-branch current-tree)))
          (else (error "Symbol is unknown: " symbol))))
-      
+
       (reverse (encode-symbol' '() tree)))
 
     (define (encode message tree)
@@ -127,11 +132,12 @@
          ((null? leaf-set) '())
          ((null? (cdr leaf-set))
           (car leaf-set))
-         (else (make-code-tree (car leaf-set)
-                               (successive-merge' (cdr leaf-set))))))
-
+         (else (make-code-tree
+                (car leaf-set)
+                (successive-merge'
+                 (cdr leaf-set))))))
       (successive-merge' (reverse leaf-set)))
-    
+
     (define (generate-huffman-tree pairs)
       (successive-merge
        (make-leaf-set pairs)))))
diff --git a/solutions/tests/exercise-2.67-tests.scm b/solutions/tests/exercise-2.67-tests.scm
@@ -1,3 +1,6 @@
+(import (srfi :64))
+(import (huffman-codes-stuff))
+
 (test-begin "2.67")
 (test-equal
     '(A D A B B C A) ;; Is this it? Did I fuck any shit up? Manuel de Coding, the Portuguese decoder, agrees with this.
diff --git a/solutions/tests/exercise-2.69-tests.scm b/solutions/tests/exercise-2.69-tests.scm
@@ -1,4 +1,15 @@
 (import (srfi :64))
+(import (huffman-codes-stuff))
+
+'(make-code-tree
+  (make-code-tree (make-leaf 'A 1)
+                  (make-leaf 'B 1))
+  (make-code-tree (make-leaf 'C 1)
+                  (make-leaf 'D 1)))
+'(((leaf A 1) (leaf B 1) (A B) 2)
+  ((leaf C 1) (leaf D 1) (C D) 2)
+  (A B C D)
+  4)
 
 (test-begin "2.69")
 (test-equal
@@ -8,4 +19,10 @@
     (make-code-tree (make-leaf 'A 1)
                     (make-leaf 'B 1))
   (generate-huffman-tree '((A 1) (B 1))))
+(test-equal
+    sample-tree
+  (generate-huffman-tree '((D 1)
+                           (C 1)
+                           (B 2)
+                           (A 4))))
 (test-end "2.69")