Add hamming exercises (closes #8)

config.json

@@ -9,6 +9,7 @@
      "leap",
      "pangram",
      "rna-transcription",
+     "hamming",
      "bob"
   ],
   "deprecated": [

elm-package.json

@@ -9,6 +9,7 @@
         "./exercises/leap",
         "./exercises/pangram",
         "./exercises/rna-transcription",
+        "./exercises/hamming",
         "./exercises/bob"
     ],
     "exposed-modules": [],

exercises/hamming/Hamming.elm

@@ -0,0 +1 @@
+module Hamming (..) where

exercises/hamming/Hamming.example

@@ -0,0 +1,14 @@
+module Hamming (..) where
+
+import String exposing (length, toList)
+
+
+distance : String -> String -> Maybe Int
+distance left right =
+  if length left /= length right then
+    Nothing
+  else
+    List.map2 (\l r -> l /= r) (toList left) (toList right)
+      |> List.filter identity
+      |> List.length
+      |> Just

exercises/hamming/HammingTests.elm

@@ -0,0 +1,60 @@
+module Main (..) where
+
+import Task
+import Console
+import ElmTest exposing (..)
+import Hamming exposing (distance)
+
+
+tests : Test
+tests =
+  suite
+    "Hamming"
+    [ test
+        "identical strands"
+        (assertEqual (distance "A" "A") (Just 0))
+    , test
+        "long identical strands"
+        (assertEqual (distance "GGACTGA" "GGACTGA") (Just 0))
+    , test
+        "complete distance in single nucleotide strands"
+        (assertEqual (distance "A" "G") (Just 1))
+    , test
+        "complete distance in small strands"
+        (assertEqual (distance "AG" "CT") (Just 2))
+    , test
+        "small distance in small strands"
+        (assertEqual (distance "AT" "CT") (Just 1))
+    , test
+        "small distance"
+        (assertEqual (distance "GGACG" "GGTCG") (Just 1))
+    , test
+        "small distance in long strands"
+        (assertEqual (distance "ACCAGGG" "ACTATGG") (Just 2))
+    , test
+        "non-unique character in first strand"
+        (assertEqual (distance "AGA" "AGG") (Just 1))
+    , test
+        "non-unique character in second strand"
+        (assertEqual (distance "AGG" "AGA") (Just 1))
+    , test
+        "large distance"
+        (assertEqual (distance "GATACA" "GCATAA") (Just 4))
+    , test
+        "large distance in off-by-one strand"
+        (assertEqual (distance "GGACGGATTCTG" "AGGACGGATTCT") (Just 9))
+    , test
+        "empty strands"
+        (assertEqual (distance "" "") (Just 0))
+    , test
+        "disallow first strand longer"
+        (assertEqual (distance "AATG" "AAA") Nothing)
+    , test
+        "disallow second strand longer"
+        (assertEqual (distance "ATA" "AGTG") Nothing)
+    ]
+
+
+port runner : Signal (Task.Task x ())
+port runner =
+  Console.run (consoleRunner tests)

exercises/hamming/elm-package.json

@@ -0,0 +1,16 @@
+{
+    "version": "1.0.0",
+    "summary": "Exercism problems in Elm.",
+    "repository": "https://github.com/exercism/xelm.git",
+    "license": "BSD3",
+    "source-directories": [
+        "."
+    ],
+    "exposed-modules": [],
+    "dependencies": {
+        "deadfoxygrandpa/elm-test": "3.0.1 <= v < 4.0.0",
+        "elm-lang/core": "2.0.0 <= v < 4.0.0",
+        "laszlopandy/elm-console": "1.1.0 <= v < 2.0.0"
+    },
+    "elm-version": "0.15.0 <= v < 0.17.0"
+}