Types

Question 1

How to get type of an expression

Answer 1

using :t operator

Question 2

How to read :: operator

Answer 2

has type of

Question 3

Evaluate :t “Hello!”

Answer 3

“Hello!” :: [Char]

Question 4

what is the meaning of -> in type definitions

Answer 4

it is read as ‘maps’ ; so if Int -> Int is seen in the type declaration, it means this function maps Int parameter to Int result

Question 5

In case of type definition of a function which are parameters and which is for output

Answer 5

Output type is specified as last item in the list separated by ->

Question 6

Define Int type

Answer 6

Stands for 32 bit integers, both +ve and -ve

Question 7

Define Integer type

Answer 7

unbounded integer size

Question 8

Define Float type

Answer 8

Single precision floating point

Question 9

Define Double type

Answer 9

Double precision floating point

Question 10

Define Bool type

Answer 10

type boolean; has only two values True and False

Question 11

Define Char type

Answer 11

used for single characters. string is a list of chars.

Question 12

What are polymorphic functions

Answer 12

functions having type variables are called polymorphic

Question 13

Difference between infix and postfix functions; provide examples

Answer 13

Oeprators are infix functionos, where the operator <param2} is the syntax for intfix functions. These are alled as operatrors as well

Question 14

Describe ‘Eq’ typeclass

Answer 14

used for types that support equality testing, Members of this type class implement == and /==. If there is a Eq in the type description of a function, it uses in its definition somewhere either == or /== operators

Question 15

What Haskell functions will not implement ‘Eq’ typeclass

Answer 15

IO functions

Question 16

Describe ‘Ord’ typeclass

Answer 16

used for types that support ordering. For example operators like , =, LT, GT, or EQ

Question 17

what is the prerequisite of ‘Ord’ typeclass members?

Answer 17

They must be part of ‘Eq’ typeclass as well.

Question 18

Describe Show typeclass

Answer 18

Members of “Show” typeclass can be presented as strings using the function show. for example show 3 will return “3”

Question 19

What are not members of ‘Show’ type class?

Answer 19

all functions

Question 20

Describe Read typeclass

Answer 20

Opposite to Show. Gets a string and returns a type which is a member of “Read”

Question 21

Evaluate read “5” - 3

Answer 21

2

Question 22

Evaluate read “[1,2,3,4]” ++ [5]

Answer 22

[1,2,3,4,5]

Question 23

Evaluate read “True” || False

Answer 23

True

Question 24

Evaluate read “4”

Answer 24

GHCI will crash, since it does not know what to do with the return value !!!

Question 25

How to specify ‘type annotations’ on read?

Answer 25

Use :: operator after the read. for example

read “4” :: Int

Question 26

Show an example of ‘type annotator’ in an expression

Answer 26

(read “5” :: Float) * 4 which will return 20.0

Question 27

why the expression read “4” crashes?

Answer 27

Since Haskell uses type inference, it has no context to infer the output type from this expression

Question 28

Define ‘Enum’ typeclass

Answer 28

Its members are types which can be ordered sequentially aka enumerated

Question 29

Describe advantages of Enum class

Answer 29

Its members types can be used in ranges;

They can also be used with succ and pred functions

Question 30

List all types in Enum class

Answer 30

(), Bool, Char, Float, Double, Int, Integer, and Ordering

Question 31

Describe Bounded typeclass

Answer 31

Member types can have an upper and lower limit

Question 32

Evaluate minBound :: Float

Answer 32

Need to check with GHCI and update the answer here

Question 33

Evaluate maxBound :: Float

Answer 33

Need to check with GHCI and update the answer here

Question 34

Evaluate minBound :: Char

Answer 34

What is the value returned by GHCI? Is this ASCII limit or something else..

Question 35

Evaluate miinBound :: (Int,Bool)

Answer 35

(-2147483648, False)

Question 36

Describe Num typeclass

Answer 36

Its members behave as numbers; So Int, Integer, Float, and Double are its members

Question 37

Describe class constraint

Answer 37

In a type description anything before => is known as class constraint. For example
:t (==)
(==) :: (Eq a) => a -> a -> Bool
Here the class constraint is saying the parameter should belong to type class Eq