Start Haskell 1st (Chapter 4)
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The document contains code definitions and examples of functions in Haskell including: - Functions to check if a character is a digit, calculate the absolute value and sign of a number, check if a number is even, and perform logical AND and NOT operations on Booleans. - Functions operating on lists and tuples like extracting the first element, testing if a list starts with a character, and mapping a function over a list. - Functions for adding numbers, doubling a value, generating odd numbers in a range, and using lambda expressions and where clauses. - Type signatures and definitions for functions like const, (+), foldr, and pattern matching examples.
![test :: [Char] -> Bool
test ['a',_,_] = True
test _ = False](https://image.slidesharecdn.com/starthaskell01chp4-key-110824190637-phpapp02/85/Start-Haskell-1st-Chapter-4-32-320.jpg)
![[1,2,3] = 1:[2,3]
________= 1:(2:[3])
________= 1:(2:(3:[]))](https://image.slidesharecdn.com/starthaskell01chp4-key-110824190637-phpapp02/85/Start-Haskell-1st-Chapter-4-35-320.jpg)
![[1,2,3] = 1:[2,3]
________= 1:(2:[3])
________= 1:(2:(3:[]))](https://image.slidesharecdn.com/starthaskell01chp4-key-110824190637-phpapp02/85/Start-Haskell-1st-Chapter-4-36-320.jpg)
![[1,2,3] = 1:[2,3]
________= 1:(2:[3])
________= 1:(2:(3:[]))
________= 1:2:3:[]](https://image.slidesharecdn.com/starthaskell01chp4-key-110824190637-phpapp02/85/Start-Haskell-1st-Chapter-4-37-320.jpg)
![test :: [Char] -> Bool
test ('a':_) = True
test _ = False](https://image.slidesharecdn.com/starthaskell01chp4-key-110824190637-phpapp02/85/Start-Haskell-1st-Chapter-4-39-320.jpg)
![test :: [Char] -> Bool
test ('a':_) = True
test _ = False](https://image.slidesharecdn.com/starthaskell01chp4-key-110824190637-phpapp02/85/Start-Haskell-1st-Chapter-4-40-320.jpg)
![odds :: Int -> [Int]
odds n = map f [0..n-1]
where f x = x * 2 + 1](https://image.slidesharecdn.com/starthaskell01chp4-key-110824190637-phpapp02/85/Start-Haskell-1st-Chapter-4-51-320.jpg)
![odds :: Int -> [Int]
odds n = map (x -> x*2+1)[0..n-1]](https://image.slidesharecdn.com/starthaskell01chp4-key-110824190637-phpapp02/85/Start-Haskell-1st-Chapter-4-52-320.jpg)
![and :: [Bool] -> Bool
and = foldr (&&) True](https://image.slidesharecdn.com/starthaskell01chp4-key-110824190637-phpapp02/85/Start-Haskell-1st-Chapter-4-58-320.jpg)
Start Haskell 1st (Chapter 4)
- 3. isDigit :: Char -> Bool isDigit c = c >= ‘0’ && c <= ‘9’
- 4. isDigit :: Char -> Bool isDigit c = c >= ‘0’ && c <= ‘9’
- 5. isDigit :: Char -> Bool isDigit c = c >= ‘0’ && c <= ‘9’
- 6. isDigit :: Char -> Bool isDigit c = c >= ‘0’ && c <= ‘9’
- 7. isDigit :: Char -> Bool isDigit c = c >= ‘0’ && c <= ‘9’
- 8. even :: Integral a => a -> Bool even n = n `mod` 2 == 0
- 9. even :: Integral a => a -> Bool even n = n `mod` 2 == 0
- 11. abs :: Int -> Int abs n = if n >= 0 then n else -n
- 12. signum :: Int -> Int signum n = if n < 0 then -1 else if n == 0 then 0 else 1
- 13. signum :: Int -> Int signum n = if n < 0 then -1 else if n == 0 then 0 else 1
- 15. abs n | n >= 0 = n ______| otherwise = -n
- 16. abs n | n >= 0 = n ______| otherwise = -n
- 17. abs n | n >= 0 = n ______| otherwise = -n
- 18. abs n | n >= 0 = n ______| otherwise = -n
- 19. signum n | n < 0 = -1 _________| n == 0 = 0 _________| otherwise = 1
- 22. not :: Bool -> Bool not False = True not True = False
- 23. not :: Bool -> Bool not False = True not True = False
- 24. not :: Bool -> Bool not False = True not True = False
- 25. (&&) :: Bool -> Bool -> Bool True && True = True True && False = False False && True = False False && False = False
- 26. (&&) :: Bool -> Bool -> Bool True && True = True _ && _ = False
- 27. (&&) :: Bool -> Bool -> Bool True && b = b False && _ = False
- 28. (&&) :: Bool -> Bool -> Bool True && b = b False && _ = False
- 29. (&&) :: Bool -> Bool -> Bool True && b = b False && _ = False
- 30. b && c | b == c = b _______| otherwise = False
- 31. fst :: (a,b) -> a fst (x,_) = x
- 32. test :: [Char] -> Bool test ['a',_,_] = True test _ = False
- 35. [1,2,3] = 1:[2,3] ________= 1:(2:[3]) ________= 1:(2:(3:[]))
- 36. [1,2,3] = 1:[2,3] ________= 1:(2:[3]) ________= 1:(2:(3:[]))
- 37. [1,2,3] = 1:[2,3] ________= 1:(2:[3]) ________= 1:(2:(3:[])) ________= 1:2:3:[]
- 39. test :: [Char] -> Bool test ('a':_) = True test _ = False
- 40. test :: [Char] -> Bool test ('a':_) = True test _ = False
- 44. x -> x + x double x = x + x
- 46. add :: (Int,Int) -> Int add x y = x + y
- 47. add :: Int -> Int -> Int add x y = x + y
- 48. add :: Int -> (Int -> Int) add x -> (y -> x + y)
- 49. const :: a -> b -> a const x _ = x
- 50. const :: a -> (b -> a) const x = _ -> x
- 51. odds :: Int -> [Int] odds n = map f [0..n-1] where f x = x * 2 + 1
- 52. odds :: Int -> [Int] odds n = map (x -> x*2+1)[0..n-1]
- 55. (+) :: Num a => a -> a -> a (+) = x -> (y -> x + y)
- 56. (+1) = x -> x + 1 (1+) = y -> 1 + y
- 57. (+) = x -> (y -> x + y) (+1) = x -> x + 1 (1+) = y -> 1 + y
- 58. and :: [Bool] -> Bool and = foldr (&&) True
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