Chapter 6: Patterns all the way down

Spring cleaning

let assert
string prefix patterns

Error(v) = problem asserts that problem is an error; if it isn't, the program crashes with a clear message. Use this when a failure would be a bug.

"Team " <> name is a string prefix pattern, right in a function head: the first clause strips the prefix, the second catches every other string.

Open in playground

pub def extract_error(problem: Result(a, b)) -> b {
  Error(v) = problem
  v
}

pub def remove_team_prefix("Team " <> name: String) -> String {
  name
}

pub def remove_team_prefix(name: String) -> String {
  name
}

pub def split_region_and_team(combined: String) -> (String, String) {
  [p1, p2] =
    combined
    |> string.split(",")

  (p1, remove_team_prefix(p2))
}

pub def main() {
  echo extract_error(Error("Not enough coffee"))
  echo remove_team_prefix("Team Turtle")
  echo split_region_and_team("East,Team Orange")
}

import gleam/string

pub fn extract_error(problem: Result(a, b)) -> b {
  let assert Error(v) = problem
  v
}

pub fn remove_team_prefix(arg_0: String) -> String {
  case arg_0 {
    "Team " <> name -> name
    name -> name
  }
}

pub fn split_region_and_team(combined: String) -> #(String, String) {
  let assert [p1, p2] = combined |> string.split(",")
  #(p1, remove_team_prefix(p2))
}

pub fn main() {
  echo extract_error(Error("Not enough coffee"))
  echo remove_team_prefix("Team Turtle")
  echo split_region_and_team("East,Team Orange")
}

src/e22_spring_cleaning.bea:23
"Not enough coffee"
src/e22_spring_cleaning.bea:24
"Turtle"
src/e22_spring_cleaning.bea:25
#("East", "Orange")

An exercism exercise from the Gleam track, solved in Bea: beacode/src/e22_spring_cleaning.bea