From b2b79ad10e1d7559f95db18af1a47f4725272aa6 Mon Sep 17 00:00:00 2001
From: bd <bdunahu@operationnull.com>
Date: Sat, 18 May 2024 20:55:32 -0600
Subject: Add prime? code and tests

---
 prime/prime.scm | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
 create mode 100755 prime/prime.scm

(limited to 'prime/prime.scm')

diff --git a/prime/prime.scm b/prime/prime.scm
new file mode 100755
index 0000000..e12dfb4
--- /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."
+  (if (< n 2)
+      #f
+      (prime-helper n (quotient n 2))))
+
+(define (prime-helper n d)
+  "Recursively checks if N is a prime number
+by attempting division by number D,D-1,D-2..."
+  (if (< d 2)
+      #t
+      (if (equal? (remainder n d) 0)
+          #f
+          (prime-helper n (- d 1)))))
-- 
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