Add (net ricketyspace sicp two twenty).

1 files changed, 14 insertions, 0 deletions

diff --git a/net/ricketyspace/sicp/two/twenty.scm b/net/ricketyspace/sicp/two/twenty.scm
new file mode 100644
index 0000000..a48704a
--- /dev/null
+++ b/net/ricketyspace/sicp/two/twenty.scm
@@ -0,0 +1,14 @@
+;;;; License: CC0-1.0
+
+(define-module (net ricketyspace sicp two twenty)
+  #:export (same-parity))
+
+(define (same-parity x . y)
+  (define x-parity (remainder x 2))
+  (define (find nums)
+    (cond ((null? nums) '())
+          ((= x-parity (remainder (car nums) 2))
+           (cons (car nums) (find (cdr nums))))
+          (else
+           (find (cdr nums)))))
+  (cons x (find y)))