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Initial task
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README.md
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README.md
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# 🎒📓💻 Task 2
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**NOTE: If you just fork this repository it will not be graded. Ask your supervisor for a special GitHub classroom URL.**
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## How to do the task
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Your task is to write a valid definition for every function declared in `src/Task.hs`. All functions have a comment describing what the function needs to do with some examples.
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There are predefined tests for you to check your answer. You can look at the tests for some more usage examples in `test/Tests.hs`.
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After defining all functions you then need to commit **and push** your code to your repository. An automated script will then check your solution and give you feedback as a CI result in your GitHub repository.
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## FAQ
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> Can I add extra functions in the `Task.hs` file?
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Yes, you can, but you can not remove existing functions.
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313
src/Task.hs
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src/Task.hs
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module Task
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(
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) where
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( -- * List Monoids
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constructFirstMonoid,
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destructFirstMonoid,
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FirstMonoid,
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constructLastMonoid,
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destructLastMonoid,
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LastMonoid,
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-- * Todo List
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Priority (..),
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Completion (..),
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TaskManager (..),
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MyTaskManager,
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-- * Coffee
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DebitCard (..),
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Coffee (..),
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CoffeeExtra (..),
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HasPrice (..),
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chargeCoffee,
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PaymentMethod (..),
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Customer (..),
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payForCoffee,
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applyPayment,
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buyCoffee,
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saveTheDiabetic,
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calculateSugarDanger,
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)
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where
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-- _ _ _ __ __ _ _
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-- | | (_)___| |_ | \/ | ___ _ __ ___ (_) __| |___
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-- | | | / __| __| | |\/| |/ _ \| '_ \ / _ \| |/ _` / __|
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-- | |___| \__ \ |_ | | | | (_) | | | | (_) | | (_| \__ \
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-- |_____|_|___/\__| |_| |_|\___/|_| |_|\___/|_|\__,_|___/
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-- Write a datatype and a Monoid instance for it such that:
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--
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-- (destructFirstMonoid . fold . fmap constructFirstMonoid) == safeHead
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--
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-- (constructFirstMonoid and destructFirstMonoid would wrap and
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-- unwrap the `FirstMonoid`)
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--
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-- In other words, it needs to have a monoid instance such that `fold`ing
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-- a list of `FirstMonoid`s should return the first element
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--
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-- >>> (destructFirstMonoid . fold . fmap constructFirstMonoid) [1, 2, 3]
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-- Just 3
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--
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-- >>> (destructFirstMonoid . fold . fmap constructFirstMonoid) []
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-- Nothing
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data FirstMonoid a
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-- Warps an `a` in a `FirstMonoid`.
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constructFirstMonoid :: a -> FirstMonoid a
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constructFirstMonoid = error "TODO: constructFirstMonoid"
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-- Unwraps the `a` from a `FirstMonoid`, if there is one.
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destructFirstMonoid :: FirstMonoid a -> Maybe a
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destructFirstMonoid = error "TODO: destructFirstMonoid"
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-- Write a datatype and a Monoid instance for it such that:
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--
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-- (destructLastMonoid . fold . fmap constructLastMonoid) == safeLast
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--
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-- (constructLastMonoid and destructLastMonoid would wrap and
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-- unwrap the `LastMonoid`)
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--
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-- In other words, it needs to have a monoid instance such that `fold`ing
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-- a list of `LastMonoid`s should return the last element
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--
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-- >>> (destructLastMonoid . fold . fmap constructLastMonoid) [1, 2, 3]
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-- Just 1
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--
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-- >>> (destructLastMonoid . fold . fmap constructLastMonoid) []
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-- Nothing
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data LastMonoid a
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-- Warps an `a` in a `LastMonoid`.
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constructLastMonoid :: a -> LastMonoid a
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constructLastMonoid = error "TODO: constructLastMonoid"
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-- Unwraps the `a` from a `LastMonoid`, if there is one.
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destructLastMonoid :: LastMonoid a -> Maybe a
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destructLastMonoid = error "TODO: destructLastMonoid"
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-- _____ _ _ _ _
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-- |_ _|__ __| | ___ | | (_)___| |_
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-- | |/ _ \ / _` |/ _ \ | | | / __| __|
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-- | | (_) | (_| | (_) | | |___| \__ \ |_
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-- |_|\___/ \__,_|\___/ |_____|_|___/\__|
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-- Your task is to create a todo list backend, which supports adding tasks,
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-- changing the priority of tasks, completing tasks, renaming tasks, and
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-- displaying tasks as a list in order of descending priority.
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-- | The priority of a task.
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data Priority = Low | Medium | High
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deriving (Show, Eq)
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-- | The completion status of a task.
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data Completion = Completed | NotCompleted
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deriving (Show, Eq)
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class TaskManager t where
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-- | Returns an empty task manager backend (it should have no tasks).
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emptyTaskManager :: t
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-- | Creates a new task with the given name and priority.
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-- Tasks are uniquely identified by their name.
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-- When a task is newly created its status should be 'NotCompleted'.
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--
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-- If there is already a task with the given name, then the
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-- behavior is undefined. (You can do whatever you want)
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createTask :: String -> Priority -> t -> t
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-- | Toggles a task with the given name.
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-- If the task has the status 'Completed', then it would become 'NotCompleted'.
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-- If the task has the status 'NotCompleted', then it would become 'Completed'.
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--
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-- Needless to say, toggling the same task twice should be
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-- equivalent to not doing anything.
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--
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-- If there is no tasks with the given name, then it does nothing.
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toggleTaskCompletion :: String -> t -> t
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-- | Removes the task with the given name.
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-- If there isn't a task with the given name, then it does nothing.
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removeTask :: String -> t -> t
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-- | Sets the priority of the task with the given name.
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-- If there isn't a task with the given name, then it does nothing.
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modifyPriority :: String -> Priority -> t -> t
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-- | Renames the task with the given name to have a new name.
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-- The first argument is the old name, the second argument is the new name.
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-- If there isn't a task with the given name, then it does nothing.
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-- If the new name clashes with an existing task, then the
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-- behavior is undefined. (You can do whatever you want)
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renameTask :: String -> String -> t -> t
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-- | Gets the list of all tasks, sorted by priority in the order:
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-- High, Medium, Low
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--
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-- Ordering of tasks with the same priority is not defined
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-- (You can do whatever you want)
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getPriorityList :: t -> [(Completion, Priority, String)]
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-- The task manager you are creating.
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data MyTaskManager
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-- TODO: You have to make your 'MyTaskManager' an instance of
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-- the 'TaskManager' typeclass.
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instance TaskManager MyTaskManager
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-- ____ __ __
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-- / ___|___ / _|/ _| ___ ___
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-- | | / _ \| |_| |_ / _ \/ _ \
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-- | |__| (_) | _| _| __/ __/
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-- \____\___/|_| |_| \___|\___|
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--
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-- /~~~~~~~~~~~~~~~~~~~/|
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-- / /######/ / |
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-- / /______/ / |
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-- ========================= /||
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-- |_______________________|/ ||
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-- | \****/ \__,,__/ ||
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-- |===\**/ __,,__ ||
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-- |______________\====/%____||
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-- | ___ /~~~~\ % / |
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-- _| |===|=== / \%_/ |
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-- | | |###| |########| | /
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-- |____\###/______\######/__|/
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-- ~~~~~~~~~~~~~~~~~~~~~~~~~~
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-- | Just a typealias to make types more readable.
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type RUBAmount = Integer
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-- | A debit card.
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-- Note: the balance can be negative.
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data DebitCard
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= DebitCard
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{ balance :: RUBAmount,
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cardId :: Int
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}
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-- | Represents a cup of coffee with extra ingredients added.
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data Coffee
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= Coffee
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{ -- | The price of the coffee itself
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-- (without the cost of the extra ingredients.)
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cost :: RUBAmount,
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-- | The extra ingredients added to the coffee.
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extras :: [CoffeeExtra]
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}
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-- Extra ingredients added to the coffee.
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data CoffeeExtra
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= Cream
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| AlmondMilk
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| SoyMilk
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| OatMilk
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| Cinnamon
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| WhiteSugar
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| BrownSugar
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-- | A typeclass representing objects, for which the price can be calculated.
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class HasPrice x where
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-- | Calculated the price of the item.
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price :: x -> RUBAmount
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-- I have already made a 'CoffeeExtra' an instance of 'HasPrice' for you.
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-- You should use this in price calculations.
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instance HasPrice CoffeeExtra where
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price Cream = 50
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price AlmondMilk = 70
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price SoyMilk = 80
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price OatMilk = 65
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price Cinnamon = 20
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price WhiteSugar = 15
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price BrownSugar = 35
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-- TODO: You want to make 'Coffee' an instance of 'HasPrice'.
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instance HasPrice Coffee
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-- | Given a coffee and a debit card, deduce the total price of the coffee from
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-- the debit card. Return the given debit card with the reduced balance.
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--
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-- If the balance of the debit card after deducing the price of the coffee
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-- would become negative, return 'Nothing' from the function.
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chargeCoffee :: Coffee -> DebitCard -> Maybe DebitCard
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chargeCoffee = error "TODO: chargeCoffee"
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-- | How was the coffee charged.
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data PaymentMethod
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= -- | The coffee was charged using a debit card.
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Card
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{ -- | The debit card with the balance deduced.
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chargedCard :: DebitCard
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}
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| -- | The coffee was charged with cash.
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Cash
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{ -- | The leftover money from the payment.
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-- (We assume that the person pays with all of the cash he has.)
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change :: RUBAmount
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}
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-- | Represents a coffee shop customer with all of the money he has on him.
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data Customer
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= Customer
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{ -- | All of the debit hards the person has on him.
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-- Sorted in order of descending preference.
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-- (He would prefer to use the first card in the list.)
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cards :: [DebitCard],
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-- | The amount of cash the customer has on him.
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cash :: RUBAmount
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}
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-- You have some new privacy-invading piece of ... technology, which
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-- automatically scans the customer, determines how he would prefer to pay and
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-- charges him automatically.
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-- | This function determines how the given customer would prefer to pay for the
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-- coffee he wants.
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--
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-- The customer would always prefer to pay with a debit card if it is possible.
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-- The customer has a strict preference in the cards he carries with him:
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-- he would always like to pay with the first card in his wallet (the list). If
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-- the first card doesn't have enough money on it, then he would prefer to use
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-- the second card, and so on.
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--
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-- If non of the cards have enough balance to cover the coffee, then the
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-- customer will have to pay in cash.
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--
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-- NOTE: The customer can only buy a coffee with strictly one payment method.
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-- (Only one card or cash)
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payForCoffee :: Customer -> Coffee -> Maybe PaymentMethod
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payForCoffee = error "TODO: payForCoffee"
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-- | This function should apply the chosen payment method to the customer.
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-- In other words, it needs to apply the charge to the customer himself
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-- (update the debit card or update the amout of cash he currently has)
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applyPayment :: Customer -> PaymentMethod -> Customer
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applyPayment = error "TODO: applyPayment"
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-- | Performs the full payment (as in 'payForCoffee') and
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-- returns the modified customer (as in 'applyPayment').
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buyCoffee :: Customer -> Coffee -> Maybe Customer
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buyCoffee = error "TODO: buyCoffee"
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-- | You know the due to a medical condition the customer needs to watch his
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-- sugar intake. The new privacy-invading piece of ... technology can now
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-- automatically apply filters to coffee orders.
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--
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-- You have to make a filter, which removes any occurrences of sugar
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-- (either WhiteSugar or BrownSugar) from the ordered cups of coffee and
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-- return the filtered orders and the amount of money the customer saves by
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-- being healthy (sugar costs money after all). So, you also have to count how
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-- much the total sugar would have cost.
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saveTheDiabetic :: [Coffee] -> (RUBAmount, [Coffee])
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saveTheDiabetic = error "TODO: saveTheDiabetic"
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-- | And just to torment those who love sugar lets make a function which
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-- calculates health hazard (sugar content) of the given orders.
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--
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-- The only ingredient that elevates the danger level is, of course, sugar:
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--
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-- WhiteSugar: 2 extra danger points
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-- BrownSugar: 1 extra danger point
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calculateSugarDanger :: [Coffee] -> Int
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calculateSugarDanger = error "TODO: calculateSugarDanger"
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