How to do it…

1. Create a new project data-types using Stack new data types. Change into the directory data-types and build the new project using stack build.

In the command prompt, run stack ghci. You will see the prompt. Enter this =:type (5 :: Int) =: command:

      *Main Lib> :type (5 :: Int)
        (5 :: Int) :: Int

:type is a GHCi command to show the type of the expression. In this case, the expression is 5. It means that the expression (5 :: Int) is Int. Now, enter this :type 5 command:

      *Main Lib> :type 5
        5 :: Num t => t

2. GHCi will interpret 5 as 5 :: Num t => t, which means that Haskell identified 5 as some numerical type t. Num t => t shows that the type is t and that it has an extra qualification, Num. Num t denotes that t is an instance of a type class Num. We will see type classes later. The Num class implements functions required for numerical calculation. Note that the result of :type 5 is different from :type (5::Int).
3. Now, enter :type (5 :: Double). You will see (5 :: Double) :: Double. Do the same thing with 5::Float:

      *Main Lib> :type (5 :: Double)
      (5 :: Double) :: Double

Note the difference between 5, 5::Int, 5::Float, and 5::Double. Without a qualification type (such as :: Int), Haskell interprets the type as a generic type Num t => t, that is, 5 is some type t, which is a Num t or numerical type.
Now enter following boolean types at the prompt:

      *Main Lib> :type True
      True :: Bool
      *Main Lib> :type False
      False :: Bool

True and False are valid boolean values, and their type is Bool. In fact, True and False are the only valid Bool values in Haskell. If you try 1 :: Bool, you will see an error:

      *Main Lib> 1 :: Bool

      <interactive>:9:1: error:
      * No instance for (Num Bool) arising from the literal 
        ‘1’
      * In the expression: 1 :: Bool
        In an equation for ‘it’: it = 1 :: Bool

Haskell will complain that 1 is a numerical type and Bool is not a numerical type, which would somehow represent it (value 1).

4. Now, type :type 'C' in the prompt. GHCi will report its type to be 'C' :: Char. Char is another data type and represents a Unicode character. A character is entered within single quotes.

5. Get more information about each type. To do this, you can enter :info <type> in the prompt:

      *Main Lib> :info Bool
      data Bool = False | True
      -- Defined in ‘ghc-prim-0.5.0.0:GHC.Types’
      instance Bounded Bool -- Defined in ‘GHC.Enum’
      instance Enum Bool -- Defined in ‘GHC.Enum’
      instance Eq Bool -- Defined in ‘ghc-prim-0.5.0.0:GHC.Classes’
      instance Ord Bool -- Defined in ‘ghc-prim-0.5.0.0:GHC.Classes’
      instance Read Bool -- Defined in ‘GHC.Read’
      instance Show Bool -- Defined in ‘GHC.Show’

This will show more information about the type. For Bool, Haskell shows that it has two values False | True and that it is defined in ghc-prim-0.5.0.0:GHC.Types. Here, ghc-prim is the package name, which is followed by its version 0.5.0.0 and then Haskell tells that GHC.Types is the module in which it is defined.