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# dbalmain's solution

## to RNA Transcription in the PureScript Track

Published at Jul 15 2018 · 0 comments
Instructions
Test suite
Solution

#### Note:

This exercise has changed since this solution was written.

# Rna Transcription

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:

• `G` -> `C`
• `C` -> `G`
• `T` -> `A`
• `A` -> `U`

## Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

### Main.purs

``````module Test.Main where

import Prelude
import Data.Maybe (Maybe(..))
import Test.Unit (TestSuite, suite, test)
import Test.Unit.Assert as Assert
import Test.Unit.Console (TESTOUTPUT)
import Test.Unit.Main (runTest)
import RNATranscription (toRNA)

main :: forall eff
. Eff ( avar :: AVAR
, console :: CONSOLE
, testOutput :: TESTOUTPUT
| eff
)
Unit
main = runTest suites

suites :: forall e. TestSuite e
suites =
suite "RNATranscription.toRNA" do
test "RNA complement of cytosine is guanine" \$
Assert.equal (Just "G") (toRNA "C")

test "RNA complement of guanine is cytosine" \$
Assert.equal (Just "C") (toRNA "G")

test "RNA complement of thymine is adenine" \$
Assert.equal (Just "A") (toRNA "T")

test "RNA complement of adenine is uracil" \$
Assert.equal (Just "U") (toRNA "A")

test "RNA complement" \$
Assert.equal (Just "UGCACCAGAAUU") (toRNA "ACGTGGTCTTAA")

test "correctly handles invalid input (RNA instead of DNA)" \$
Assert.equal Nothing (toRNA "U")

test "correctly handles completely invalid DNA input" \$
Assert.equal Nothing (toRNA "XXX")

test "correctly handles partially invalid DNA input" \$
Assert.equal Nothing (toRNA "ACGTXXXCTTAA")``````
``````module RNATranscription
( toRNA
) where

import Prelude

import Data.Maybe (Maybe(..))
import Data.String.CodeUnits (fromCharArray, toCharArray)
import Data.Traversable (sequence)

toRnaChar âˆ· Char â†’ Maybe Char
toRnaChar 'C' = Just 'G'
toRnaChar 'G' = Just 'C'
toRnaChar 'T' = Just 'A'
toRnaChar 'A' = Just 'U'
toRnaChar _ = Nothing

toRNA âˆ· String â†’ Maybe String
toRNA dna =
toCharArray dna
# map toRnaChar
# sequence
# map fromCharArray``````

### What can you learn from this solution?

A huge amount can be learned from reading other peopleâ€™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.

• What compromises have been made?