net: Add (net ricketyspace sicp two thirty)

1 files changed, 33 insertions, 0 deletions

diff --git a/net/ricketyspace/sicp/two/thirty.scm b/net/ricketyspace/sicp/two/thirty.scm
new file mode 100644
index 0000000..ffb22fa
--- /dev/null
+++ b/net/ricketyspace/sicp/two/thirty.scm
@@ -0,0 +1,33 @@
+;;;; License: CC0-1.0
+
+(define-module (net ricketyspace sicp two thirty)
+  #:export (square-tree
+            square-tree-steroids))
+
+(define (square-tree tree)
+  (cond ((null? tree) '())
+        ((not (pair? tree)) (* tree tree))
+        (else (cons (square-tree (car tree))
+                    (square-tree (cdr tree))))))
+
+(define (square-tree-steroids tree)
+  (map (lambda (sub-tree)
+         (if (not (pair? sub-tree))
+             (* sub-tree sub-tree)
+             (square-tree-steroids sub-tree)))
+       tree))
+
+
+;;; Guile REPL
+;;;
+;;; scheme@(guile-user)> ,use (net ricketyspace sicp two thirty)
+;;; scheme@(guile-user)> (square-tree
+;;;                       (list 1
+;;;                             (list 2 (list 3 4) 5)
+;;;                             (list 6 7)))
+;;; $6 = (1 (4 (9 16) 25) (36 49))
+;;; scheme@(guile-user)> (square-tree-steroids
+;;;                       (list 1
+;;;                             (list 2 (list 3 4) 5)
+;;;                             (list 6 7)))
+;;; $7 = (1 (4 (9 16) 25) (36 49))