Testing the Option type in Gleam

optiontest.gleam.rs

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

type PersonalName {
  PersonalName(
    first_name: String,
    middle_initial: result.Option(String),
    last_name: String,
  )
};

fn get_personal_names() -> List(PersonalName) {
  [
    PersonalName(
      first_name: "John",
      middle_initial: result.none(),
      last_name: "Doe",
    ),
    PersonalName(
      first_name: "Homer",
      middle_initial: Ok("J"),
      last_name: "Simpson",
    ),
  ]
}

fn to_label(name) -> String {
  case name {
    PersonalName(
      first_name,
      Error(Nil),
      last_name,
    ) -> first_name
      |> string.append(" ")
      |> string.append(last_name)
    PersonalName(
      first_name,
      Ok(middle_initial),
      last_name,
    ) -> first_name
      |> string.append(" ")
      |> string.append(middle_initial)
      |> string.append(". ")
      |> string.append(last_name)
  }
}

// => ["John Doe", "Homer J. Simpson"]
pub fn get_labelled_names() -> List(String) {
  get_personal_names()
  |> list.map(to_label)
}

optiontest2.gleam.rs

import gleam/list
import gleam/string

type Option(a) {
  Some(a)
  None
};

type PersonalName {
  PersonalName(
    first_name: String,
    middle_initial: Option(String),
    last_name: String,
  )
};

fn get_personal_names() -> List(PersonalName) {
  [
    PersonalName(
      first_name: "John",
      middle_initial: None,
      last_name: "Doe",
    ),
    PersonalName(
      first_name: "Homer",
      middle_initial: Some("J"),
      last_name: "Simpson",
    ),
  ]
}

fn to_label(name) -> String {
  case name {
    PersonalName(
      first_name,
      None,
      last_name,
    ) -> first_name
      |> string.append(" ")
      |> string.append(last_name)
    PersonalName(
      first_name,
      Some(middle_initial),
      last_name,
    ) -> first_name
      |> string.append(" ")
      |> string.append(middle_initial)
      |> string.append(". ")
      |> string.append(last_name)
  }
}

// => ["John Doe", "Homer J. Simpson"]
pub fn get_labelled_names() -> List(String) {
  get_personal_names()
  |> list.map(to_label)
}