Added nucleotide-count exercise.

config.json

@@ -16,7 +16,8 @@
       "robot-name",
       "rna-transcription",
       "atbash-cipher",
-      "raindrops"
+      "raindrops",
+      "nucleotide-count"
    ],
   "deprecated": [
 

exercises/nucleotide-count/example.el

@@ -0,0 +1,19 @@
+;;; nucleotide-count.el --- nucleotide-count Exercise (exercism)
+
+;;; Commentary:
+
+;;; Code:
+
+
+(defun nucleotide-count (sequence)
+  (let ((counts (copy-alist '((?A . 0) (?C . 0) (?G . 0) (?T . 0)))))
+    (dolist (i (append sequence nil))
+      (let ((n (assoc i counts)))
+        (if n
+            (setcdr n (1+ (cdr n)))
+          (error "Invalid nucleotide '%c'" i))))
+    counts))
+
+
+(provide 'nucleotide-count)
+;;; nucleotide-count.el ends here

exercises/nucleotide-count/nucleotide-count-test.el

@@ -0,0 +1,34 @@
+;;; nucleotide-count-test.el --- Tests for nucleotide-count (exercism)
+
+;;; Commentary:
+
+;;; Code:
+
+(load-file "nucleotide-count.el")
+
+
+(defun sort-pairs (lst fn)
+  (sort lst (lambda (a b) (funcall fn (car a) (car b)))))
+
+
+(ert-deftest empty-dna-strand-has-no-nucleotides-test ()
+  (should (equal (sort-pairs (nucleotide-count "") #'<)
+                 '((?A . 0) (?C . 0) (?G . 0) (?T . 0)))))
+
+
+(ert-deftest repetitive-sequence-has-only-guanine-test ()
+  (should (equal (sort-pairs (nucleotide-count "GGGGGGGG") #'<)
+                 '((?A . 0) (?C . 0) (?G . 8) (?T . 0)))))
+
+
+(ert-deftest count-all-nucleotides-test ()
+  (should (equal (sort-pairs (nucleotide-count "AGCTTTTCATTCTGACTGCAACGGGCAATATGTCTCTGTGTGGATTAAAAAAAGAGTGTCTGATAGCAGC") #'<)
+                 '((?A . 20) (?C . 12) (?G . 17) (?T . 21)))))
+
+
+(ert-deftest invalid-nucleotide-test ()
+  (should-error (nucleotide-count "AGGTCCXGA")))
+
+
+(provide 'nucleotide-count)
+;;; nucleotide-count-test.el ends here

exercises/nucleotide-count/nucleotide-count.el

@@ -0,0 +1,9 @@
+;;; nucleotide-count.el --- nucleotide-count Exercise (exercism)
+
+;;; Commentary:
+
+;;; Code:
+
+
+(provide 'nucleotide-count)
+;;; nucleotide-count.el ends here