types

• basic data types:

  Bool: True False

  Integer: ... -1 0 1 ...

  Int: -9223372036854775808 ... 9223372036854775807

  Float, Doubles: 0.123 -4.5e6

  Char: 'a' ... 'A' ... '1' ...

  String: "Hello World" "yolo"
• create new types:

  data TwoStrings = TwoStr String String
• data TwoStrings = TwoStr String String

  TwoStrings is the new type

  TwoStr is a constructor
• type of function: length

  Foldable t => t a -> Int
• type of function: product

  (Foldable t, Num a) => t a -> a
• type of function: sum

  [Int] -> Int
• type of function: head

  [a] -> a
• type of function: tail

  [a] -> [a]
• func :: ?

  func 0 = []

  func n = n : func (n-1)

  Int -> [Int]
• func :: ?

  func = [(1, 'a'), (2, 'b'), (3, 'c'), (4, 'd'), (5 ,'e')]

  [(Int, Char)]
• func :: ?

  func x [] = [x]

  func x (y:ys) = y : func x ys

  Int -> [Int] -> [Int]
• :t map

  (a -> b) -> [a] -> [b]
• :t filter

  (a -> Bool) -> [a] -> [a]
• :t zip

  [a] -> [b] -> [(a, b)]
• :t unzip

  [(a, b)] -> ([a], [b])
• :t zipWith

  (a -> b -> c) -> [a] -> [b] -> [c]