learning-sicp

commit 003b86c2d451d4fff198dc983ea584bd2798ced9
parent 95d9109ee298e00aba7940524f076e37bf56c744
Author: Yuval Langer <yuval.langer@gmail.com>
Date:   Mon, 27 Mar 2023 17:47:47 +0300

A bit better solution to exercise 2.69.

Diffstat:
M
sicp/solutions/exercise-1.21.scm
 | 
2
+-
M
sicp/solutions/exercise-2.40.scm
 | 
16
+++++++++-------
M
sicp/solutions/huffman-codes-stuff.scm
 | 
11
++++++-----

3 files changed, 16 insertions(+), 13 deletions(-)
diff --git a/sicp/solutions/exercise-1.21.scm b/sicp/solutions/exercise-1.21.scm
@@ -1,4 +1,4 @@
-(define-library (solutions exercise-1.21)
+(define-library (sicp solutions exercise-1.21)
   (import (scheme base))
   (import (srfi srfi-1))
   (import (srfi srfi-64))
diff --git a/sicp/solutions/exercise-2.40.scm b/sicp/solutions/exercise-2.40.scm
@@ -1,9 +1,11 @@
-(define-library (solutions exercise-2.40)
+(define-library (sicp solutions exercise-2.40)
   (import (scheme base))
-  (import (srfi :1))
-  (import (sicp utils))
-  (import (solutions exercise-1.21))
-  (export unique-pairs prime-sum-pairs my-prime-sum-pairs)
+  (import (only (sicp utils) filter))
+  (import (only (sicp solutions exercise-1.21) prime?))
+  (export my-prime-sum-pairs
+          prime-sum-pairs
+          remove
+          unique-pairs)
   
   (begin
     (define (unique-pairs n)
@@ -13,7 +15,7 @@
                       (enumerate-interval 1 (- i 1))))
                (enumerate-interval 1 n)))
 
-    (define (remove item seqeunce)
+    (define (remove item sequence)
       (filter (lambda (x)
                 (not (equal? x
                              item)))
@@ -36,7 +38,7 @@
        (map (lambda (i)
               (map (lambda (j)
                      (list i j))
-                   (enumerate 1 (- i 1))))
+                   (enumerate-interval 1 (- i 1))))
             (enumerate-interval 1 n))))
 
     (define (g n)
diff --git a/sicp/solutions/huffman-codes-stuff.scm b/sicp/solutions/huffman-codes-stuff.scm
@@ -1,7 +1,10 @@
 (define-library (sicp solutions huffman-codes-stuff)
   (import (scheme base))
+  (import (scheme process-context))
+  (import (scheme write))
   (import (scheme cxr))
-  (import (sicp utils))
+  (import (only (sicp utils) accumulate))
+  (import (only (sicp solutions exercise-2.40) remove))
   (export make-code-tree
           make-leaf
           sample-message
@@ -146,8 +149,7 @@
                       (car leaf-set)
                       leaf-set))
         (define leaf-set-without-minimal-weighted-leaf
-          (filter (lambda (x) (not (equal? minimal-weighted-leaf
-                                           x)))
+          (remove minimal-weighted-leaf
                   leaf-set))
         (define next-to-minimal-weighted-leaf
           (accumulate (lambda (x y) (if (< (weight x)
@@ -160,8 +162,7 @@
           (cons (make-code-tree
                  next-to-minimal-weighted-leaf
                  minimal-weighted-leaf)
-                (filter (lambda (x) (not (equal? next-to-minimal-weighted-leaf
-                                                 x)))
+                (remove next-to-minimal-weighted-leaf
                         leaf-set-without-minimal-weighted-leaf)))
 
         results)