Learning Exercise
When pattern matching on a value in Gleam we have to ensure the patterns match every possible value of the type, otherwise the code won't compile.
This function should be rejected as it has not handled case where the list is empty:
pub fn get_first_element_or_crash(items: List(e)) -> e {
case items {
[item, ..] -> item
}
}
Most of the time in Gleam programs we want to handle every possible case, but in some programs such as prototypes and quick scripts we may want to focus only on the happy path and not write code for other cases. This is where Gleam's let assert comes in.
With let assertions a pattern can match only some of the possible values of a type, and if the pattern does not match a value the program will crash. Using let assert we can write the above function like this:
pub fn get_first_element_or_crash(items: List(e)) -> e {
let assert [item, ..] = items
item
}
Gleam libraries should never use let assertions as they can crash the program. Instead, they should use the Result type and let the application developer decide how to handle errors.
Mika the events organiser has got a promotion at work, and as part of her new responsibilities she is in charge of the events database. She quickly noticed that a lot of the data is stored in ways that make it hard to work with, so you're teaming up to clean it up with a one-off script.
Because the script is only going to be run once, and you are confident about the structure of the data, you feel this is a good place to use Gleam's let assertions.
Each past event has a list of problems that occurred during the event. These have been stored as results, but they're always the Error variant.
Implement the extract_error function which takes a result that is expected to always be an Error and returns the contained error value.
extract_error(Error("Not enough coffee"))
// -> "Not enough coffee"
Team names have been prefixed with the word "Team ", but this is not needed. Implement the remove_team_prefix function to remove the prefix from a team name.
remove_team_prefix("Team Turtle")
// -> "Turtle"
Each event is run by a team, and each team belongs to a region. In the database they are stored in a single string, separated by a comma.
Implement the split_region_and_team function to split the string into a tuple of two strings, one for the region and one for the team. The prefix "Team " should be removed from the team name.
split_region_and_team("East,Team Orange")
// -> #("East", "Orange")
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