128 lines
3.9 KiB
Markdown
128 lines
3.9 KiB
Markdown
# Valentine's Day
|
|
|
|
Welcome to Valentine's Day on Exercism's Gleam Track.
|
|
If you need help running the tests or submitting your code, check out `HELP.md`.
|
|
If you get stuck on the exercise, check out `HINTS.md`, but try and solve it without using those first :)
|
|
|
|
## Introduction
|
|
|
|
## Custom Types
|
|
|
|
Custom Types are how new data types are defined in Gleam. They can have multiple _variants_, each with their own name.
|
|
|
|
```gleam
|
|
pub type Season {
|
|
Spring
|
|
Summer
|
|
Autumn
|
|
Winter
|
|
}
|
|
```
|
|
|
|
Each case of a custom type can optionally hold some data, and different cases can have different types of data. When a variant holds data it is called a _record_.
|
|
|
|
```gleam
|
|
pub type Number {
|
|
SomeInt(Int)
|
|
SomeFloat(Float)
|
|
Invalid
|
|
}
|
|
```
|
|
|
|
Creating a value for a specific case can be done by referring to its name if it contains no additional data (`Spring`), or by calling it as a function if it does (`SomeInt(2)`).
|
|
|
|
```gleam
|
|
let spring = Spring
|
|
let integerTwo = SomeInt(2)
|
|
```
|
|
|
|
Custom types, along with everything in Gleam, have _structural equality_, which means that two values of the same variant and with the same data are equivalent.
|
|
|
|
```gleam
|
|
Spring == Spring // -> True
|
|
Spring == Autumn // -> False
|
|
SomeInt(2) == SomeInt(2) // -> True
|
|
SomeInt(2) == SomeFloat(2.0) // -> False
|
|
```
|
|
|
|
Custom type variants can be pattern matched on using case expressions.
|
|
|
|
```gleam
|
|
import gleam/int
|
|
import gleam/float
|
|
|
|
pub fn describe(flexible_number: Number) -> String {
|
|
case flexible_number {
|
|
SomeFloat(f) -> "Float: " <> float.to_string(f)
|
|
SomeInt(i) -> "Int: " <> int.to_string(i)
|
|
Invalid -> "Neither a float nor an int"
|
|
}
|
|
}
|
|
```
|
|
|
|
## Instructions
|
|
|
|
In this exercise, it's Valentine's day and you and your partner are planning on doing something nice together. Your partner has lots of ideas, and is now asking you to rate the ideas, in order to find the activity to engage in.
|
|
|
|
The following ideas are proposed by your partner:
|
|
|
|
- Playing a board game
|
|
- Chill out
|
|
- Watch a movie
|
|
- Go to a restaurant
|
|
- Take a walk
|
|
|
|
You have six tasks to help choose your Valentine's day activity.
|
|
|
|
## 1. Define the approval
|
|
|
|
For each idea your partner proposes, you respond with one of three options: yes, no or maybe.
|
|
|
|
Define the `Approval` custom type to represent these options as the following three cases: `Yes`, `No` and `Maybe`.
|
|
|
|
## 2. Define the cuisines
|
|
|
|
Your partner has selected two possible restaurants: one based on the Korean cuisine and the other based on the Turkish cuisine.
|
|
|
|
Define the `Cuisine` custom type to represent these cuisines as the following two cases: `Korean` and `Turkish`.
|
|
|
|
## 3. Define the movie genres
|
|
|
|
There are tons of movies to choose from, so to narrow things down, your partner also lists their genre.
|
|
|
|
Define the `Genre` custom type to represent the following genres as cases: `Crime`, `Horror`, `Romance` and `Thriller`.
|
|
|
|
## 4. Define the activity
|
|
|
|
As said, your partner has come up with five different activities: playing a board game, chill out, watch a movie, go to a restaurant and taking a walk.
|
|
|
|
Define the `Activity` custom type to represent these activity types:
|
|
|
|
- `BoardGame`: no associated data.
|
|
- `Chill`: no associated data.
|
|
- `Movie`: has its `Genre` as associated data.
|
|
- `Restaurant`: has its `Cuisine` as associated data.
|
|
- `Walk`: has an `Int` representing the number of kilometers to walk as associated data.
|
|
|
|
## 5. Rate the activity
|
|
|
|
Finally, you're ready to rate your partner's ideas. This is how you feel about your partner's idea:
|
|
|
|
- Playing a board game: no.
|
|
- Chill out: no.
|
|
- Watch a movie: yes if it is a romantic movie; otherwise, no.
|
|
- Go to a restaurant: yes if the cuisine is Korean, maybe if it is Turkish.
|
|
- Take a walk: yes if the walk is more than eleven kilometers; maybe if it is more than six kilometers; otherwise, no.
|
|
|
|
Implement a function named `rate_activity` that takes an `Activity` value and returns the `Approval` based on the above sentiments:
|
|
|
|
```gleam
|
|
rate_activity(Restaurant(Turkish))
|
|
// -> Maybe
|
|
```
|
|
|
|
## Source
|
|
|
|
### Created by
|
|
|
|
- @lpil |