MCQs on Advanced Types and Typeclasses | Haskell
In Haskell programming, typeclasses are a core concept that allow developers to define and use polymorphic functions. Understanding typeclass basics like Eq, Show, Ord, and Functor, as well as how to define custom typeclasses and ensure they adhere to certain laws, is essential for effective Haskell programming. This guide provides a set of 30 multiple-choice questions to help you test and deepen your knowledge of these topics.
MCQs on Advanced Types and Typeclasses in Haskell Programming
Typeclass Basics (Eq, Show, Ord, Functor, etc.)
- Which of the following typeclasses does the
==operator belong to in Haskell?- A) Show
- B) Eq
- C) Ord
- D) Functor
- What is the purpose of the
Showtypeclass in Haskell?- A) To compare values
- B) To convert values to strings
- C) To enable pattern matching
- D) To map values to other values
- The
Ordtypeclass is used for:- A) Representing values as strings
- B) Sorting and comparing values
- C) Applying functions to values
- D) Implementing functors
- Which of the following types is an instance of the
Functortypeclass?- A) Int
- B) Maybe
- C) Bool
- D) Char
- What does the
Ordtypeclass allow us to do?- A) Print values as strings
- B) Compare values for ordering
- C) Map functions over data types
- D) Create functors
- What is the method associated with the
Eqtypeclass?- A)
show - B)
== - C)
compare - D)
fmap
- A)
- The
Functortypeclass requires which method to be defined?- A)
fmap - B)
== - C)
show - D)
compare
- A)
- Which typeclass is responsible for converting a type to a string in Haskell?
- A) Eq
- B) Show
- C) Ord
- D) Functor
- What does the
Eqtypeclass help determine?- A) If two values are equal
- B) If one value is greater than another
- C) How to represent a value as a string
- D) How to map over a data structure
- Which of the following is an instance of the
Showtypeclass in Haskell?- A) Int
- B) Function
- C) Tuple
- D) All of the above
Defining Custom Typeclasses
- How do you define a custom typeclass in Haskell?
- A)
class MyClass {} - B)
typeclass MyClass {} - C)
class MyClass a where - D)
newtype MyClass a where
- A)
- When defining a custom typeclass, which keyword is used to define methods?
- A)
def - B)
func - C)
instance - D)
where
- A)
- Which of the following is the correct syntax for declaring a custom method in a typeclass?
- A)
methodName :: a -> b - B)
methodName a = b - C)
methodName a => b - D)
methodName a -> b
- A)
- If you define a custom typeclass, what must you do next to use it with specific types?
- A) Declare instances for those types
- B) Use
fmap - C) Use
==operator - D) Import the typeclass
- How do you create an instance for a custom typeclass for a particular type?
- A)
instance MyClass a where - B)
instance (a) MyClass - C)
type MyClass a = instance - D)
class MyClass instance
- A)
- Which keyword is used to create an instance of a typeclass for a specific type in Haskell?
- A)
instance - B)
define - C)
implement - D)
use
- A)
- If a custom typeclass method uses a type parameter
a, what does it mean in the context of the typeclass?- A) It works for all types
a - B) It only works for
aspecifically - C) It represents a specific typeclass
- D) It means the method is overloaded
- A) It works for all types
- What happens if you try to use a custom typeclass method without defining it in an instance?
- A) The code compiles successfully
- B) An error is thrown
- C) The method is applied to default values
- D) The program behaves unpredictably
- Which of the following is an example of defining a custom typeclass in Haskell?
- A)
class Eq a where (==) :: a -> a -> Bool - B)
class Show a where show :: a -> String - C)
class Add a where add :: a -> a -> a - D) All of the above
- A)
- Which typeclass would you define for a type that has a notion of adding two values together?
- A) Eq
- B) Show
- C) Add
- D) Functor
Understanding Typeclass Laws and Instances
- Which of the following is a requirement for an instance of the
Eqtypeclass?- A) Reflexivity:
x == x - B) Transitivity:
x == yandy == zimpliesx == z - C) Symmetry:
x == yimpliesy == x - D) All of the above
- A) Reflexivity:
- Which of the following is NOT part of the laws for defining a valid
Functorinstance?- A)
fmap id == id - B)
fmap (f . g) == fmap f . fmap g - C)
fmap f == fmap g - D) Both A and B are valid
- A)
- What is the law associated with
Functorthat ensures composition behaves as expected?- A) Functor law of equivalence
- B) Functor law of identity
- C) Functor law of composition
- D) Functor law of distributivity
- If a type
ais an instance of theEqtypeclass, what must the function==satisfy?- A) Symmetry
- B) Reflexivity
- C) Transitivity
- D) All of the above
- Which of the following is required to define a valid instance of the
Ordtypeclass?- A) Reflexivity
- B) Anti-symmetry
- C) Transitivity
- D) All of the above
- What would happen if a type’s instance of
Eqviolates one of its laws?- A) The program will compile, but logic errors may occur
- B) The program will not compile
- C) The instance will be ignored
- D) The program will crash
- Which of the following statements is true about typeclass laws?
- A) They are optional for defining instances
- B) They ensure that typeclass instances behave predictably
- C) They are only relevant for built-in typeclasses like
Eq - D) They only apply to custom types
- What does the
Ordtypeclass law enforce?- A) Consistency in value ordering
- B) Symmetry in comparisons
- C) Associativity of comparison
- D) All of the above
- Which of the following ensures that a custom typeclass method behaves consistently across different types?
- A) Adherence to typeclass laws
- B) Multiple definitions for the same method
- C) Use of specific data types
- D) None of the above
- What is the primary purpose of typeclass laws in Haskell?
- A) To define the methods of a typeclass
- B) To guarantee predictable behavior of typeclass instances
- C) To create new types
- D) To improve the performance of typeclass instances
Answers
| Qno | Answer (Option with the text) |
|---|---|
| 1 | B) Eq |
| 2 | B) To convert values to strings |
| 3 | B) Sorting and comparing values |
| 4 | B) Maybe |
| 5 | B) Compare values for ordering |
| 6 | B) == |
| 7 | A) fmap |
| 8 | B) Show |
| 9 | A) If two values are equal |
| 10 | D) All of the above |
| 11 | C) class MyClass a where |
| 12 | D) where |
| 13 | A) methodName :: a -> b |
| 14 | A) Declare instances for those types |
| 15 | A) instance MyClass a where |
| 16 | A) instance |
| 17 | A) It works for all types a |
| 18 | B) An error is thrown |
| 19 | D) All of the above |
| 20 | C) Add |
| 21 | D) All of the above |
| 22 | C) fmap f == fmap g |
| 23 | C) Functor law of composition |
| 24 | D) All of the above |
| 25 | D) All of the above |
| 26 | A) The program will compile, but logic errors may occur |
| 27 | B) They ensure that typeclass instances behave predictably |
| 28 | A) Consistency in value ordering |
| 29 | A) Adherence to typeclass laws |
| 30 | B) To guarantee predictable behavior of typeclass instances |