Functional Programming in Haskell
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Questions and Answers

What is the output of the greetPerson function when it is called with person1?

  • Hello, 25!
  • Hello, Alice! (correct)
  • Hello, Person!
  • Hello, Bob!

The Person data type has fields for 'name' and 'age'.

True (A)

What is the purpose of the greetPerson function?

To return a greeting message that includes the person's name.

The first person in the example is named __________.

<p>Alice</p> Signup and view all the answers

Match the following example outputs to their corresponding person:

<p>Hello, Alice! = person1 Hello, Bob! = person2</p> Signup and view all the answers

What is the output of the function isAdult when person1 is 20?

<p>True (B)</p> Signup and view all the answers

The constructor name in Haskell can be the same as the type name without causing confusion.

<p>False (B)</p> Signup and view all the answers

What is the minimum age for a person to be considered an adult according to the given function?

<p>18</p> Signup and view all the answers

In Haskell, a Shape can be either a Circle with a radius or a __________ with height and width.

<p>Rectangle</p> Signup and view all the answers

Match the Haskell data types with their descriptions:

<p>Person = Represents a person's name and age Shape = Defines geometric figures such as circles and rectangles Individual = Alternative name to avoid naming overlap with Person Circle = Represents a shape defined by its radius</p> Signup and view all the answers

What is the type of a Basket in Haskell?

<p>[ShopItem] (D)</p> Signup and view all the answers

A Basket can contain mixed types of values due to Haskell's type system.

<p>False (B)</p> Signup and view all the answers

What are the two components of a ShopItem?

<p>A String for the item name and an Int for the item price.</p> Signup and view all the answers

The function countItems returns 0 if the basket is _____?

<p>empty</p> Signup and view all the answers

Match the following elements with their descriptions:

<p>Basket = A list of ShopItems ShopItem = A tuple containing item name and price countItems = Function to count items in a basket Type Alias = A way to create a synonym for a type</p> Signup and view all the answers

Which component type does Haskell treat the price of a ShopItem as?

<p>Int (C)</p> Signup and view all the answers

Haskell's strong typing allows for type mismatches to occur at runtime.

<p>False (B)</p> Signup and view all the answers

What does the countItems function use to check how many items there are in a Basket?

<p>Pattern matching</p> Signup and view all the answers

What does the function flipH do?

<p>Flips the picture horizontally (B)</p> Signup and view all the answers

What is the purpose of the countItems function in the context provided?

<p>To count each item in a list (D)</p> Signup and view all the answers

Algebraic Types (ATs) can be defined using the keyword 'define'.

<p>False (B)</p> Signup and view all the answers

The function printPicture will modify the original picture.

<p>False (B)</p> Signup and view all the answers

What does the function totalPrice return when the basket is empty?

<p>0</p> Signup and view all the answers

What type is defined for a Picture?

<p>Picture = [[Char]]</p> Signup and view all the answers

An example of an Algebraic Type is data Person = Person { name :: ______, age :: Int }.

<p>String</p> Signup and view all the answers

The function beside combines two pictures by placing them ______.

<p>side-by-side</p> Signup and view all the answers

Match the following functions with their descriptions:

<p>printPicture = Displays a picture flipH = Flips the picture horizontally flipV = Flips the picture vertically invertColour = Inverts the colors of the picture</p> Signup and view all the answers

Match the following functions or concepts with their purposes:

<p>countItems = Counts items in a basket totalPrice = Calculates total price of items Algebraic Types = Define custom types with named constructors Tuples = Group multiple values together without labels</p> Signup and view all the answers

Which line is responsible for flipping the picture vertically?

<p>flipV pic = [ reverse line | line &lt;- pic ] (C)</p> Signup and view all the answers

Which statement highlights a benefit of using Algebraic Types over Tuples?

<p>Algebraic Types offer controlled construction. (A)</p> Signup and view all the answers

The invertColour function uses map to invert each row.

<p>True (A)</p> Signup and view all the answers

The totalPrice function adds up the price of each item in the basket.

<p>True (A)</p> Signup and view all the answers

What character represents a black pixel in the defined Picture type?

<h1></h1> Signup and view all the answers

What is the main advantage of clear labeling in Algebraic Types?

<p>Improved readability and purpose indication</p> Signup and view all the answers

What is the output of the function isRound when given a Rectangle?

<p>False (A)</p> Signup and view all the answers

The Maybe type can represent a value and an absence of a value.

<p>True (A)</p> Signup and view all the answers

What does the function area return for a Circle with radius 3?

<p>28.274333882308138</p> Signup and view all the answers

The general form for defining a data type is data Typename = Con1 ______ | Con2 ______.

<p>t11...t1k1</p> Signup and view all the answers

Match the following Haskell constructs with their descriptions:

<p>isRound = Function that checks if a shape is round Maybe = Type that handles optional values area = Function that calculates area of shapes Rectangle = Constructor representing a rectangle shape</p> Signup and view all the answers

What does area (Rectangle h w) return?

<p>h * w (B)</p> Signup and view all the answers

Constructors in Haskell can't take arguments.

<p>False (B)</p> Signup and view all the answers

What is a key benefit of using polymorphic types?

<p>Reusability across types</p> Signup and view all the answers

Flashcards

List

A collection of elements of the same type, represented by square brackets and a type annotation. For example, ["apple", "banana"] is a list of type [String].

Tuple

A data structure that holds two or more values of different types. For example, ("apple", 1) is a tuple with a String and an Int.

Type Alias

A type alias creates a new name for an existing type. This improves code readability and allows for more flexible type definitions.

Type Consistency

The concept of using consistent types throughout a program, ensuring that all elements in a data structure have the same type. This allows Haskell to predict the types of values and prevent runtime errors.

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countItems function

A function that takes a Basket as input and returns the number of items in the basket.

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Pattern Matching

A technique for checking the type of a value and branching the execution flow based on the type. This helps in ensuring type-safe code and allows for specific actions depending on the value’s type.

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ShopItem

A type that represents the type of an item in a shopping basket. It is defined as a tuple (String, Int) where String represents the item name and Int represents the item price.

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Basket

A type that represents a collection of ShopItems. It is defined as a list of ShopItems, using the type alias Basket = [ShopItem].

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Algebraic Types

A powerful feature in Haskell that allows you to define custom data types with specific properties and constructors. This lets you model complex structures and concepts in your code.

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Prelude

A built-in module in Haskell that provides a collection of standard functions and data types used frequently in programming.

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Product Types

A type of algebraic data type used to represent combinations of different types, similar to a tuple but with named fields.

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Defining Data Types

The process of defining custom data types using algebraic types, allowing for the creation of structured data representations within a program.

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Data Type and Constructor Naming Convention in Haskell

A specific way to structure data types in which both the type and its constructor have the same name. This can lead to confusion. (Example: data Person = Person Name Age).

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Custom Type

Haskell allows defining custom data types for different purposes. For example, you can create a Shape type with subtypes Circle and Rectangle, each with their own inherent data structure.

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Algebraic Types (ATs)

Custom data types defined using the data keyword in Haskell. They allow for more meaningful data modeling compared to primitive types.

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Why ATs are better than Tuples

ATs provide clear labels for objects, ensuring type-safe construction and preventing accidental misuse.

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Data Keyword

Allows creating data structures with a predefined structure, like a Person with a name and age.

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Named Constructors

Named constructors enable the creation of objects of a specific type. They act as functions that create instances with specific attributes.

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Type Synonyms

Used to define aliases for existing types, providing shorthand notation without defining new types.

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Improved Error Messages in ATs

Provide meaningful information in error messages, making debugging easier and more efficient.

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Recursive Data Definitions

ATs allow for recursive definitions, enabling the creation of self-referential data structures, while type synonyms are limited to simple aliases.

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Controlled Construction in ATs

Each item in an AT is created using a specified constructor, ensuring type-safety and controlled construction.

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isRound

A function that checks if a given shape is a circle.

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area

A function that calculates the area of a given shape.

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Maybe

A data type that can hold either a value of a specific type or represent the absence of a value.

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Nothing

It represents the absence of a value within the 'Maybe' data type.

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String

A data type that represents a sequence of characters, enclosed in double quotes. For example, "Hello, world!" is a string.

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Picture

A data type representing a two-dimensional array of characters, where each element is a row of the picture.

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printPicture

A function that takes a Picture as input and displays it on the screen, printing each row of characters.

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flipH

A function that flips a Picture horizontally, like reflecting it in a mirror.

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flipV

A function that flips a Picture vertically, like viewing it upside down.

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beside

A function that combines two Pictures side by side, creating a wider picture.

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above

A function that places two Pictures one above the other, creating a taller picture.

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invertColour

A function that inverts the colors of a picture, swapping black pixels for white and vice versa.

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Study Notes

  • Functional Programming covers the use of tuples and pattern matching.
  • Learning objectives include tuples, Algebraic Types in Haskell, and Prelude library usage.
  • A custom type alias, ShopItem, is defined as (String, Int).
  • ShopItem allows use cases for items in a shop to be represented using tuples for item names (String) and prices (Int, in cents).
  • Defining items (e.g., "Salt: 1kg", 139) allows for declaring their type as ShopItem.
  • A list of items, a basket, can be demonstrated using ShopItem types.
  • The concept of algebraic types (ATs) in Haskell and how they are defined allows for custom types with named constructors.
  • ATs model data better than primitive types.
  • ATs are defined using the keyword data.
  • Data types like data Bool = True | False are examples of enum types which are helpful for representing sets of values.
  • Data types such as data Person = Person {name :: String, age :: Int} are examples of product types that combine multiple values into a single type.
  • Haskell's prelude includes functions like map, filter, and foldr for data manipulation that operate on types such as lists.
  • map function applies a function to each element in a list.
  • filter function filters elements in a list based on a predicate, returning a list of matched elements.
  • foldr reduces a list to a single value.
  • putStrLn is an I/O function that utilizes monads for sequencing actions.
  • Function composition is possible using the $ operator to chain functions.
  • Pictures can be represented using a 2D grid of characters, with a Picture type defined as [[Char]].
  • printPicture function displays a picture.
  • flipH function horizontally flips a picture.
  • flipV function vertically flips a picture.
  • above function stacks pictures vertically.
  • beside function places pictures side-by-side.
  • Functions can be composed together to create more complex functionality.
  • The Maybe type is for handling potential failures (e.g., safe division).
  • The Maybe type can have a value (using Just) or no value (Nothing).

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Functional Programming Types and Pattern Matching - PDF

Description

This quiz covers functional programming concepts focusing on tuples, pattern matching, and algebraic types in Haskell. You'll explore how to define custom types like ShopItem and use them to represent items in a shop, as well as the benefits of algebraic types over primitive types. Test your understanding of the Prelude library and data type definitions.

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