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authorrsiddharth <s@ricketyspace.net>2017-07-15 22:19:51 +0000
committerrsiddharth <s@ricketyspace.net>2017-07-15 22:19:51 +0000
commit30535ec1f959d828241b0f9863709587094ddeec (patch)
tree0b74f258f659966395675e0d490f47b1938f3d00 /net
parentab2ecb49ace565beb3f1393a59da7b7e3b399828 (diff)
net: Add (net ricketyspace sicp one twentythree).
* net/ricketyspace/sicp/one/twentythree.scm (net ricketyspace sicp one twentythree): Add module.
Diffstat (limited to 'net')
-rw-r--r--net/ricketyspace/sicp/one/twentythree.scm25
1 files changed, 25 insertions, 0 deletions
diff --git a/net/ricketyspace/sicp/one/twentythree.scm b/net/ricketyspace/sicp/one/twentythree.scm
new file mode 100644
index 0000000..f88b05d
--- /dev/null
+++ b/net/ricketyspace/sicp/one/twentythree.scm
@@ -0,0 +1,25 @@
+;;;; Under Creative Commons Attribution-ShareAlike 4.0
+;;;; International. See
+;;;; <https://creativecommons.org/licenses/by-sa/4.0/>.
+
+(define-module (net ricketyspace sicp one twentythree)
+ #:use-module (net ricketyspace sicp utils)
+ #:export (smallest-divisor))
+
+(define (square x)
+ (expt x 2))
+
+(define (divides? a b)
+ (= (remainder b a) 0))
+
+(define (next n)
+ (cond ((= n 2) 3)
+ (else (+ n 2))))
+
+(define (find-divisor n test-divisor)
+ (cond ((> (square test-divisor) n) n)
+ ((divides? test-divisor n) test-divisor)
+ (else (find-divisor n (next test-divisor)))))
+
+(define (smallest-divisor n)
+ (find-divisor n 2))