Outline
- ● Side-scrolling game
- ● Rotating background
- ● Working with an infinite universe
- ● Generating random infinite universe
Inferring types
Exercise 6.1.
What is the type of the following definitions? Provide the most general type. Verify your answer against the compiler.
exercise_6_1_a = 2 + 3
exercise_6_1_b (x, y) = sqrt (x^2 + y^2)
exercise_6_1_c x y = [x, y]
exercise_6_1_d [] = "" exercise_6_1_d (x:xs) = exercise4 xs ++ [x]
exercise_6_1_e x = (x, x)
Wrapper types
Exercise 6.2.
Consider the following type declarations representing cartesian and polar coordinates of a 2D point. Implement conversion functions.
data Cartesian = Cartesian Double Double data Radians = Double
data Polar = Polar Double Radians
toPolar :: Cartesian -> Polar fromPolar :: Polar -> Cartesian
Higher-order functions
Exercise 6.3.
Implement higher-order function concentric, that renders concentric shapes. Using concentric, render a picture of practice target:
main :: IO () main = drawingOf
(concentric targetCircle 10)
Algebraic data types + stateful computation
Exercise 6.4.
Consider the following type of commands. Implement a function that follows a sequence of commands to render a picture.
type Radians = Double
data Command
= Forward Double
| Rotate Radians
| TeleportTo (Double, Double)
runCommands :: [Command] -> Picture
main = drawingOf (runCommands [ Rotate (2*pi/3), Forward 2, Forward (-4) , TeleportTo (0, 0), Rotate (2*pi/3), Forward 2 ])
Input and output in Haskell
Exercise 6.5.
Implement an interactive program that records every user input and allows to search history via command /search <phrase>. Use Data.List.isInfixOf to search for previous inputs matching the search phrase. Example (user input is bold):
input> something to record
input> something else to record
input> Haskell is strongly statically typed
input> lazy evaluation is useful in purely-functional languages input> /search something
Found 2 records:
– something to record
– something else to record
Generating lists
Exercise 6.6(a)
Implement function renderCartesianGrid:
renderCartesianGrid :: (Double, Double) -> (Double, Double) -> Picture
main :: IO () main = drawingOf
(renderCartesianGrid
(-5.5, 5.5)
(-5.5, 5.5))
Generating lists
Exercise 6.6(b)
Implement function renderPolarGrid:
renderPolarGrid :: Double -> Int -> Picture
main :: IO () main = drawingOf
(renderPolarGrid 5.5 5)
