Cleanup prime?

1 files changed, 17 insertions, 0 deletions

diff --git a/prime?/prime.scm b/prime?/prime.scm
new file mode 100755
index 0000000..3d08a35
--- /dev/null
+++ b/prime?/prime.scm
@@ -0,0 +1,17 @@
+(define-module (prime))
+
+
+(define-public (prime? n)
+  "Returns #t if N is prime, else #f."
+
+  (define (prime-helper n d)
+    "Recursively checks if N is a prime number
+by attempting division by number D,D-1,D-2..."
+    (cond
+     ((< d 2) #t)
+     ((zero? (remainder n d)) #f)
+     (#t (prime-helper n (1- d)))))
+
+  (if (< n 2)
+      #f
+      (prime-helper n (quotient n 2))))