MCQs on Control Structures | Haskell
Control structures in Haskell programming provide a foundation for decision-making, pattern matching, and iterative processing through recursion and list comprehensions. Learning to effectively use conditional expressions, pattern matching, and recursion enables functional programmers to create efficient and readable code. Explore these concepts with 30 multiple-choice questions designed to enhance your Haskell expertise.
MCQs on Control Structures in Haskell
Conditional Expressions (if, else, guard)
- What is the correct syntax for an
ifexpression in Haskell?- a)
if condition then expr1 else expr2 - b)
if condition { expr1 } else { expr2 } - c)
if (condition) { expr1 } else { expr2 } - d)
if (condition): expr1 else: expr2
- a)
- What type must the
thenandelseexpressions have in anifexpression?- a) They can have different types.
- b) They must be functions.
- c) They must have the same type.
- d) They must return integers.
- What happens if the
elsebranch is missing in anifexpression?- a) It throws a compile-time error.
- b) It defaults to
Nothing. - c) It defaults to
()(unit). - d) The program crashes at runtime.
- Which construct in Haskell is equivalent to multiple
if-elseconditions?- a) Pattern matching
- b) Guards
- c) Lambda functions
- d) Case expressions
- In guards, what operator is used to define a condition?
- a)
= - b)
<- - c)
| - d)
->
- a)
- How are guards evaluated in a function definition?
- a) From bottom to top
- b) In random order
- c) From top to bottom
- d) Based on priority
- Which is the correct guard for a function to check if a number is positive?
- a)
| x > 0 = True - b)
if x > 0 then True - c)
-> x > 0 = True - d)
: x > 0 = True
- a)
Pattern Matching (with case and function clauses)
- What is pattern matching primarily used for in Haskell?
- a) Iterating through lists
- b) Decomposing data structures
- c) Validating conditions
- d) Writing loops
- Which keyword is used for pattern matching in Haskell?
- a)
match - b)
case - c)
switch - d)
guard
- a)
- How does pattern matching handle unmatched cases?
- a) It returns
Nothing. - b) It throws a runtime error.
- c) It evaluates to
()(unit). - d) It retries with the last case.
- What does the wildcard
_signify in pattern matching?
- a) Match any value without binding it.
- b) Match specific values.
- c) Exclude certain values.
- d) A special constant.
- How can you match the head and tail of a list in Haskell?
- a)
x : xs - b)
x -> xs - c)
head x, tail xs - d)
[x | xs]
- What is the result of
case [1, 2, 3] of [] -> "Empty"; x:xs -> "Non-empty"?
- a)
"Empty" - b)
"Non-empty" - c) Runtime error
- d)
"1"
- Which function clause will correctly match an empty list?
- a)
myFunc [x] = ... - b)
myFunc [] = ... - c)
myFunc x:xs = ... - d)
myFunc [x:xs] = ...
- How can you explicitly specify all unmatched cases in a
caseexpression?
- a) Using
_as the last pattern - b) Adding an
elsebranch - c) Using a guard condition
- d) Declaring
default
Recursion: Base Case, Recursive Case, and Termination
- What is the base case in recursion?
- a) The part where recursion stops
- b) The part where the function calls itself
- c) A loop in functional programming
- d) A condition that triggers infinite recursion
- What happens if a recursive function does not include a base case?
- a) It throws a compile-time error.
- b) It causes infinite recursion.
- c) It returns
Nothing. - d) It automatically stops after 10 iterations.
- Which of the following is an example of a recursive function?
- a)
factorial n = if n == 0 then 1 else n * factorial (n - 1) - b)
factorial n = n * 2 - c)
factorial n = n + 1 - d)
factorial n = map (*n) [1..n]
- What is the key property of tail-recursive functions?
- a) They use constant stack space.
- b) They cannot return values.
- c) They are more readable.
- d) They only handle numeric data.
- How do you terminate a recursive function in Haskell?
- a) Return a base case value.
- b) Use
break. - c) Use
stop. - d) Declare it as
main.
List Comprehensions
- What is the primary purpose of list comprehensions in Haskell?
- a) Filtering and transforming lists
- b) Performing string concatenations
- c) Implementing loops
- d) Matching patterns
- Which symbol is used to define a generator in a list comprehension?
- a)
<- - b)
-> - c)
: - d)
=
- What is the result of
[x*2 | x <- [1, 2, 3]]?
- a)
[2, 4, 6] - b)
[1, 2, 3] - c)
[4, 8, 12] - d)
[3, 6, 9]
- How can you filter elements in a list comprehension?
- a) By adding a condition after the generator
- b) By using
caseexpressions - c) By using
ifexpressions only - d) By applying
map
- What does
[x | x <- [1, 2, 3], x > 2]return?
- a)
[3] - b)
[1, 2, 3] - c)
[2, 3] - d)
[]
- Which keyword is used in list comprehensions to combine multiple generators?
- a)
and - b)
let - c)
then - d) None, multiple generators are separated by commas.
- What does
[x + y | x <- [1, 2], y <- [3, 4]]return?
- a)
[4, 5, 5, 6] - b)
[3, 4, 5, 6] - c)
[4, 5] - d)
[1, 2, 3, 4]
- Can list comprehensions in Haskell be nested?
- a) Yes
- b) No
- Which of the following is NOT true about list comprehensions?
- a) They can work with infinite lists.
- b) They cannot use conditional filtering.
- c) They are a declarative way of generating lists.
- d) They support multiple generators.
- What is a common use case for list comprehensions in Haskell?
- a) Generating prime numbers
- b) Filtering a list
- c) Transforming lists
- d) All of the above
Here are the answers to the MCQs on Control Structures in Haskell:
| Qno | Answer |
|---|---|
| 1 | a) if condition then expr1 else expr2 |
| 2 | c) They must have the same type |
| 3 | a) It throws a compile-time error |
| 4 | b) Guards |
| 5 | c) ` |
| 6 | c) From top to bottom |
| 7 | a) ` |
| 8 | b) Decomposing data structures |
| 9 | b) case |
| 10 | b) It throws a runtime error |
| 11 | a) Match any value without binding it |
| 12 | a) x : xs |
| 13 | b) "Non-empty" |
| 14 | b) myFunc [] = ... |
| 15 | a) Using _ as the last pattern |
| 16 | a) The part where recursion stops |
| 17 | b) It causes infinite recursion |
| 18 | a) factorial n = if n == 0 then 1 else n * factorial (n - 1) |
| 19 | a) They use constant stack space |
| 20 | a) Return a base case value |
| 21 | a) Filtering and transforming lists |
| 22 | a) <- |
| 23 | a) [2, 4, 6] |
| 24 | a) By adding a condition after the generator |
| 25 | a) [3] |
| 26 | d) None, multiple generators are separated by commas |
| 27 | a) [4, 5, 5, 6] |
| 28 | a) Yes |
| 29 | b) They cannot use conditional filtering |
| 30 | d) All of the above |