Exercises

03. Types and Typeclasses

Using IHaskell: https://github.com/gibiansky/IHaskell

For this exercise, we are dealing with a type for colours of the rainbow
The typeclass is defined here, and note its English spelling.
For more information on how this is done, look ahead to:
http://learnyouahaskell.com/making-our-own-types-and-typeclasses

Have a play with the Colour in ghci, try the succ and pred functions and so on.

Again, you should be able to write these functions in one line,
using the information from the chapter http://learnyouahaskell.com/types-and-typeclasses
and the chapter before



In [ ]:

    
data Colour = Red | Orange | Yellow | Green | Blue | Indigo | Violet
    deriving (Eq, Ord, Show, Bounded, Enum)

1. The Colour typeclass is of type Ord. What is the "first" (or least) colour?



In [ ]:

    
firstColour = undefined

-- Test
firstColour == Red

2. List the colours in reverse order



In [ ]:

    
reverseColourOrder = undefined

-- Test
reverseColourOrder == [Violet,Indigo,Blue,Green,Yellow,Orange,Red]

3. Mix two colours together, to produce the average value of the two

Example: paintMix Orange Green = Yellow
If necessary, favour the "higher" value when computing the average.
For example: paintMix Green Violet = Indigo

Hint: Integer division can be performed with the quot function: quot 7 2 = 3



In [ ]:

    
paintMix c1 c2 = undefined

-- Test
paintMix Green Violet == Indigo