learning-haskell/05-types/5.8-chapter-excercises.md

Chapter Excercises

Multiple choice

1. (c)
2. (a)
3. (b)
4. (c)

Determine the type

2. Num a => a
3. Num a => (a, [Char])
4. (Integer, [Char])
5. Bool
6. Int
7. Bool
8. Num a => a
9. Num a => a -> a
10. Fractional a => a
11. [Char]

Does it compile?

1. The definition of wahoo tries to apply a Num to another Num which does not work. Either change bigNum to take an argument (bigNum x = (^) 5 $ x ; wahoo = bigNum $ 10) or fix wahoo, e.g. wahoo = bigNum 2.Nothing wrong here.
2. c tries to apply 5 to b = 5 which does not work. It's also expected to take an argument in the definition of d = c 200. A fix could thus be: c = a 10.
3. c is not defined for the definition of b.

Type variable or specific type constructor?

1. /
2. zed is fully polymorphic, Zed and Blah are concrete.
3. a is fully polymorphic, b is constrained and C is concrete.
4. f and g are fully polymorphic and C is concrete.

Write a type signature

1. functionH :: [a] -> a
2. functionC :: (Ord a) => a -> a -> Bool
3. functionS :: (a, b) -> b

Given a type, write the function

see src/defineFunc.hs

Fix it

1. see src/sing.hs
2. see src/sing.hs
3. see src/arith3broken.hs

Type-Kwon-Do

see src/typekwondo.hs