From 4a013aa17d8dbeca7f07d50e1f7d2dc0ad60d5d0 Mon Sep 17 00:00:00 2001
From: Markus Bertheau <mbertheau@gmail.com>
Date: Fri, 22 May 2015 23:27:43 +0200
Subject: [PATCH] Add hamming exercise

---
 config.json              |  3 ++-
 hamming/example.rkt      |  8 ++++++++
 hamming/hamming-test.rkt | 41 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 51 insertions(+), 1 deletion(-)
 create mode 100644 hamming/example.rkt
 create mode 100644 hamming/hamming-test.rkt

diff --git a/config.json b/config.json
index 6dc26b3..099cf1a 100644
--- a/config.json
+++ b/config.json
@@ -4,6 +4,7 @@
   "repository": "https://github.com/exercism/xracket",
   "active": false,
   "problems": [
-    "bob"
+    "bob",
+    "hamming"
   ]
 }
diff --git a/hamming/example.rkt b/hamming/example.rkt
new file mode 100644
index 0000000..dcb6e71
--- /dev/null
+++ b/hamming/example.rkt
@@ -0,0 +1,8 @@
+#lang racket
+
+(define (hamming-distance dna1 dna2)
+  (unless (= (string-length dna1) (string-length dna2))
+    (raise-argument-error 'hamming-distance "strings of equal length" 1 dna1 dna2))
+  (count (compose not eqv?) (string->list dna1) (string->list dna2)))
+
+(provide hamming-distance)
diff --git a/hamming/hamming-test.rkt b/hamming/hamming-test.rkt
new file mode 100644
index 0000000..ffd5890
--- /dev/null
+++ b/hamming/hamming-test.rkt
@@ -0,0 +1,41 @@
+#lang racket
+
+(require rackunit
+         rackunit/text-ui
+         "hamming.rkt")
+
+(define suite
+  (test-suite
+    "Tests for the hamming exercise"
+    (check-equal? 0 (hamming-distance "A" "A")
+                  "identical strands")
+    (check-equal? 0 (hamming-distance "GGACTGA" "GGACTGA")
+                  "long identical strands")
+    (check-equal? 1 (hamming-distance "A" "G")
+                  "complete distance in single nucleotide strands")
+    (check-equal? 2 (hamming-distance "AG" "CT")
+                  "complete distance in small strands")
+    (check-equal? 1 (hamming-distance "AT" "CT")
+                  "small distance in small strands")
+    (check-equal? 1 (hamming-distance "GGACG" "GGTCG")
+                  "small distance")
+    (check-equal? 2 (hamming-distance "ACCAGGG" "ACTATGG")
+                  "small distance in long strands")
+    (check-equal? 1 (hamming-distance "AGA" "AGG")
+                  "non-unique character in first strand")
+    (check-equal? 1 (hamming-distance "AGG" "AGA")
+                  "non-unique character in second strand")
+    (check-equal? 4 (hamming-distance "GATACA" "GCATAA")
+                  "large distance")
+    (check-equal? 9 (hamming-distance "GGACGGATTCTG" "AGGACGGATTCT")
+                  "large distance in off-by-one strand")
+    (check-equal? 0 (hamming-distance "" "")
+                  "empty strands")
+    (check-exn #rx"strings of equal length"
+               (thunk (hamming-distance "AATG" "AAA"))
+               "disallow first strand longer")
+    (check-exn #rx"strings of equal length"
+               (thunk (hamming-distance "ATA" "AGTG"))
+               "disallow second string longer")))
+
+(exit (if (zero? (run-tests suite)) 0 1))