Given a DNA strand, return its RNA complement (per RNA transcription).
Both DNA and RNA strands are a sequence of nucleotides.
The four nucleotides found in DNA are adenine (A), cytosine (C), guanine (G) and thymine (T).
The four nucleotides found in RNA are adenine (A), cytosine (C), guanine (G) and uracil (U).
Given a DNA strand, its transcribed RNA strand is formed by replacing each nucleotide with its complement:
Refer to the Installing Elm page for information about installing elm.
The first time you start an exercise, you'll need to ensure you have the appropriate dependencies installed. Thankfully, Elm makes that easy for you and will install dependencies when you try to run tests or build the code.
Execute the tests with:
Automatically run tests again when you save changes:
$ elm-test --watch
As you work your way through the test suite, be sure to remove the
calls from each test until you get them all passing!
It is possible to submit an incomplete solution so you can see how others have completed the exercise.
module Tests exposing (tests) import Expect import RNATranscription exposing (toRNA) import Test exposing (..) tests : Test tests = describe "RNATranscription" [ test "complement of cytosine is guanine" <| \() -> Expect.equal (Ok "G") (toRNA "C") , skip <| test "complement of guanine is cytosine" <| \() -> Expect.equal (Ok "C") (toRNA "G") , skip <| test "complement of thymine is adenine" <| \() -> Expect.equal (Ok "A") (toRNA "T") , skip <| test "complement of adenine is uracil" <| \() -> Expect.equal (Ok "U") (toRNA "A") , skip <| test "complement" <| \() -> Expect.equal (Ok "UGCACCAGAAUU") (toRNA "ACGTGGTCTTAA") ]
module RNATranscription exposing (toRNA) import Dict exposing (Dict) toRNA : String -> Result Char String toRNA dna = dna |> String.foldr rnaTranscription (Ok "") -- PRIVATE rnaTranscription : Char -> Result Char String -> Result Char String rnaTranscription dna acc = let transcription = rnaTranscriptions |> Dict.get dna in case transcription of Just rna -> acc |> Result.map (String.cons rna) Nothing -> Err dna rnaTranscriptions : Dict Char Char rnaTranscriptions = Dict.fromList [ ( 'A', 'U' ) , ( 'C', 'G' ) , ( 'G', 'C' ) , ( 'T', 'A' ) ]
A huge amount can be learned from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.
Here are some questions to help you reflect on this solution and learn the most from it.