Add elisp/hamming

elisp/hamming/hamming.el

@@ -0,0 +1,26 @@
+;;; hamming.el --- Hamming (exercism)
+
+;;; Commentary:
+
+;;; Code:
+
+(provide 'hamming)
+
+(defun count-different-chars(s1 s2)
+  "Count the number of different characters between two strings, S1 and S2, which must be of equal length."
+  (let ((count 0) (i 0))
+    (while (< i (length s1))
+      (if (not (char-equal (aref s1 i) (aref s2 i)))
+          (setq count (+ count 1)))
+      (setq i (+ i 1)))
+    count))
+
+(defun hamming-distance(s1 s2)
+  "Determine the Hamming distance of two strands of DNA.
+Expects the strands as two strings, S1 and S2,
+which must be of equal length."
+  (cond ((string= s1 s2) 0)
+        ((eq (length s1) (length s2)) (count-different-chars s1 s2))
+        (error  "Strands must be of equal length")))
+
+;;; hamming.el ends here