grouped with map and takeWhile

Protein Translation
Protein Translation in Scala 
object ProteinTranslation {

  def proteins(input: String): Seq[String] = {
    input.grouped(3).map(codonsToProteins).takeWhile(_ != "STOP").toSeq
  }

  private def codonsToProteins(codon: String): String = {

    codon match {
      case "AUG"                         => "Methionine"
      case "UUU" | "UUC"                 => "Phenylalanine"
      case "UUA" | "UUG"                 => "Leucine"
      case "UCU" | "UCC" | "UCA" | "UCG" => "Serine"
      case "UAU" | "UAC"                 => "Tyrosine"
      case "UGU" | "UGC"                 => "Cysteine"
      case "UGG"                         => "Tryptophan"
      case "UAA" | "UAG" | "UGA"         => "STOP"
    }
  }
}

This approach starts by calling the grouped() method on the input String. It will take a sequence of Chars up to the amount passed in.

Caution

The grouped() treats a String as a plain sequence of Char code units and makes no attempt to keep surrogate pairs or codepoint sequences together. The user is responsible for making sure such cases are handled correctly. Failing to do so may result in an invalid Unicode String. The grouped() method works here because all of the characters are ASCII.

If the remaining number of Charss is less than the argument, grouped() will return those, and will be an empty Iterator if no Chars are left. The Chars are chained to the map() method which passes them to the codonsToProteins() method, which accepts them as a String.

The codonsToProteins() method uses a match to look up the protein for the codon and returns the protein from the method.

The proteins are chained to the takeWhile() method which keeps requesting codons until they run out or a STOP codon is received.

Once all of the valid codons have been translated, the proteins() method returns a sequence of the proteins.

8th May 2024 · Found it useful?

Other Approaches to Protein Translation in Scala

Other ways our community solved this exercise
private def codonsToProteins(input: String, proteins: Seq[String]): Seq[String] = {
    if (input.length < 3)
      proteins
    else
      codonToProtein(input.take(3)) match {
        case "STOP" => proteins
        case protein =>
          codonsToProteins(input.drop(3), proteins :+ protein)}}
if and else with match and recursion

Use if and else with match and recursion to return the answer.