Add rna-transcription exercise (closes #10)

config.json

@@ -8,6 +8,7 @@
      "hello-world",
      "leap",
      "pangram",
+     "rna-transcription",
      "bob"
   ],
   "deprecated": [

elm-package.json

@@ -8,6 +8,7 @@
         "./exercises/hello_world",
         "./exercises/leap",
         "./exercises/pangram",
+        "./exercises/rna-transcription",
         "./exercises/bob"
     ],
     "exposed-modules": [],

exercises/rna-transcription/RNATranscription.elm

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

exercises/rna-transcription/RNATranscription.example

@@ -0,0 +1,28 @@
+module RNATranscription (toRNA) where
+
+import String
+
+
+toRNA : String -> Result Char String
+toRNA dna =
+  dna
+    |> String.toList
+    |> List.map toRNANucleotide
+    |> resultExtraCombine
+    |> Result.map (List.map String.fromChar)
+    |> Result.map (String.join "")
+
+
+-- Copied from elm-result-extra
+resultExtraCombine : List (Result x a) -> Result x (List a)
+resultExtraCombine = List.foldr (Result.map2 (::)) (Ok [])
+
+
+toRNANucleotide : Char -> Result Char Char
+toRNANucleotide nuc =
+  case nuc of
+    'C' -> Ok 'G'
+    'G' -> Ok 'C'
+    'A' -> Ok 'U'
+    'T' -> Ok 'A'
+    _ -> Err nuc

exercises/rna-transcription/RNATranscriptionTests.elm

@@ -0,0 +1,39 @@
+module Main (..) where
+
+import Task
+import Console
+import ElmTest exposing (..)
+import RNATranscription exposing (toRNA)
+
+
+tests : Test
+tests =
+  suite
+    "RNATranscription"
+    [ test
+        "complement of cytosine is guanine"
+        (assertEqual (Ok "G") (toRNA "C"))
+    , test
+        "complement of guanine is cytosine"
+        (assertEqual (Ok "C") (toRNA "G"))
+    , test
+        "complement of thymine is adenine"
+        (assertEqual (Ok "A") (toRNA "T"))
+    , test
+        "complement of adenine is uracil"
+        (assertEqual (Ok "U") (toRNA "A"))
+    , test
+        "complement"
+        (assertEqual (Ok "UGCACCAGAAUU") (toRNA "ACGTGGTCTTAA"))
+    , test
+        "correctly handles completely invalid input"
+        (assertEqual (Err 'X') (toRNA "XXX"))
+    , test
+        "correctly handles partially invalid input"
+        (assertEqual (Err 'U') (toRNA "UGAAXXXGACAUG"))
+    ]
+
+
+port runner : Signal (Task.Task x ())
+port runner =
+  Console.run (consoleRunner tests)

exercises/rna-transcription/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"
+}