playground

//// Convert DNA to RNA

import gleam/list
import gleam/result
import gleam/string

/// A function that accepts dna as a string and
/// returns a Result with either rna as a string or Nil
pub fn to_rna(dna: String) -> Result(String, Nil) {
  dna
  |> string.to_graphemes
  |> list.try_map(complement)
  |> result.map(string.concat)
}

/// A helper function that accepts a char for DNA and
/// returns a Result of a char or Nil
fn complement(nucleotide: String) -> Result(String, Nil) {
  case nucleotide {
    "C" -> Ok("G")
    "G" -> Ok("C")
    "T" -> Ok("A")
    "A" -> Ok("U")
    _ -> Error(Nil)
  }
}