PROBLEM 1
    = = = = =

  1. 1477           = 1477 :: Num a => a

  2. 3+2            = 5 :: Num a => a

  3. 15/2           = 7.5 :: Fractional a => a

  4. div 15 2       = 7 :: Integral a => a

  5. 15 `div` 2     = 7 :: Integral a => a

  6. 15 div 2       = <interactive>:11:1:  (ERROR?)

  7. 15.0 / 2.0     = 7.5 :: Fractional a => a

  8. 15.0 `div` 2.0 = <interactive>:13:1: No instance for (Fractional a0) arising from a use of ‘it’  (ERROR?)

  9. 13.4 / 1.8     = 7.444444444444445 :: Fractional a => a 

 10. 2.71 > 5.67    = False :: Bool

 11. "x" ++ "yz"    = "xyz" :: [Char]

 12. x ++ "yz"      = <interactive>:20:1: Not in scope: ‘x’  (ERROR?)

 13. show 7         = "7" :: String

 14. read "7" :: Integer                  = 7 :: Integer

 15. truncate 23.6                        = 23 :: Num a => a

 16. take 4 "Computer Science!"           = "Comp" :: [Char] 

 17. drop 4 "Computer Science!"           = "uter Science!" :: [Char] 

 18. take 7 drop 9 "Computer Science!"    = <interactive>:30:1: Couldn't match expected type  (ERROR?)

 19. take 7 (drop 9 "Computer Science!")  = "Science" :: [Char] 

 20. "kalle" >= "andersson"               = True :: Bool

 21. "anders" < "andersson"               = True :: Bool

 22. length "soffbord"            = 8 :: Int

 23. 2 >= 6 || 2.71 > 5.67        = False :: Bool

 24. 2 >= 6 || 2.71 < 5.67        = True :: Bool

 25. 65 < 150 || 19               = <interactive>:37:13: No instance for (Num Bool)  (ERROR?)

 26. 1 `div` 0 < 3 && 2.0 < 1.0   = *** Exception: divide by zero

 27. 2.0 < 1.0 && 1 `div` 0 < 3   = False :: Bool

 28. not (2.71 > 5.67)            = True :: Bool


    PROBLEM 2
    = = = = =

  1. /          (/) :: Fractional a => a -> a -> a  - division operator

  2. div        div :: Integral a => a -> a -> a

  3. >          (>) :: Ord a => a -> a -> Bool      - greater-than operator

  4. >=         (>=) :: Ord a => a -> a -> Bool     - greater-than-or-equal operator

  5. ||         (||) :: Bool -> Bool -> Bool        - OR operator

  6. not        not :: Bool -> Bool

  7. ++         (++) :: [a] -> [a] -> [a]           - concatenation operator

  8. take       take :: Int -> [a] -> [a]
Hoogλe:
take n, applied to a list xs, returns the prefix of xs of length n, or xs itself if n > length xs:
 > take 5 "Hello World!" == "Hello"
 > take 3 [1,2,3,4,5] == [1,2,3]
 > take 3 [1,2] == [1,2]
 > take 3 [] == []
 > take (-1) [1,2] == []
 > take 0 [1,2] == []
It is an instance of the more general Data.List.genericTake, in which n may be of any integral type.

  9. drop       drop :: Int -> [a] -> [a]
Hoogλe:
drop n xs returns the suffix of xs after the first n elements, or [] if n > length xs:
 > drop 6 "Hello World!" == "World!"
 > drop 3 [1,2,3,4,5] == [4,5]
 > drop 3 [1,2] == []
 > drop 3 [] == []
 > drop (-1) [1,2] == [1,2]
 > drop 0 [1,2] == [1,2]
It is an instance of the more general Data.List.genericDrop, in which n may be of any integral type.

 10. truncate   truncate :: (Integral b, RealFrac a) => a -> b
Hoogλe:
 truncate :: (RealFrac a, Integral b) => a -> b

 11. length     length :: Foldable t => t a -> Int
Hoogλe:
 O(n). length returns the length of a finite list as an Int. It is an instance of the 
more general Data.List.genericLength, the result type of which may be any kind of number.


    PROBLEM 3
    = = = = =

  1. round 3.4          3 :: Integral b => b

  2. (round)3.4         3 :: Integral b => b

  3. round3.4           <interactive>:62:1:  Not in scope:

  4. round 3.4 + 10.0   <interactive>:63:1:  No instance for (Fractional a0) 

  5. round(3.4 + 10.0)  13 :: Integral b => b

  6. 1 + 2 * 3          7 :: Num a => a

  7. (1 + 2) * 3        9 :: Num a => a

  8. 3 * 2 + 1          7 :: Num a => a

  9. (3 * 2) + 1        7 :: Num a => a

 10. 7+6                13 :: Num a => a

 11. 7 + 6              13 :: Num a => a

 12. 17 `div` 3         5 :: Integral a => a

 13. div (17 3)         <interactive>:72:1:  Non type-variable argument in the constraint

 14. not (not True)     True :: Bool

 15. (not not) True     <interactive>:75:1:  Couldn't match expected type ‘Bool -> t’ with actual type ‘Bool’
                        <interactive>:75:6:  Couldn't match expected type ‘Bool’ with actual type ‘Bool -> Bool’


    PROBLEM 4
    = = = = =

  1. let pi = 3.1415927
      <no-reply>

  2. let radius = 5.0
      <no-reply>

  3. let area = pi * radius * radius
      <no-reply>

  4. area
      78.5398175 :: Fractional a => a