forked from runarfu/haskell-workshop
/
E02_Functions.hs
83 lines (65 loc) · 2.21 KB
/
E02_Functions.hs
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
module E02_Functions where
import Common
{-
In this module we will learn how to define and apply functions.
-}
-- Defining a function taking one parameter:
welcome name = "Welcome, " ++ name ++ "."
-- ^ ^ `------------^------------'
-- name parameter body
{-
There's no keyword like "def", "function" or anything preceding the name, just:
<functionName> <arguments> = <body>
-}
-- Calling a function with arguments
welcomeSirOrMadam = welcome "Sir or Madam"
{-
Now if we do multiple function applications and intend on passing the result
of the first application to the second application and so on, we would have to
use parentheses to remove ambiguities:
-}
printWelcomeMessage2 = putStrLn (welcome "Welcome to the present")
{-
otherwise the compiler would interpret that function this way:
printWelcomeMessage2 = (putStrLn welcome) "Welcome to the present"
^ ^ ^
function to apply arg arg to what (putstrln welcome) returned
So a general tip is: if in doubt, add parentheses!
-}
{-
Exercise:
Use the multiply function to return the product of 10 and 20.
Fill in your answer as the body of multiply10by20.
-}
-- This function returns the product of its arguments:
multiply arg1 arg2 = arg1 * arg2
multiply10by20 = _YOUR_CODE_HERE
{-
Exercise:
Define a function, plus, that takes two arguments and returns their sum
-}
plus :: Integer -> Integer -> Integer
plus arg1 arg2 = _YOUR_CODE_HERE
{-
Exercise:
Define a function, sum3, that takes 3 arguments and returns their sum.
... and you must use the plus function to do so!
-}
sum3 :: Integer -> Integer -> Integer -> Integer
sum3 arg1 arg2 arg3 = _YOUR_CODE_HERE
{-
Exercise:
Define isDollar that takes a Char and returns
True only if that character is a dollar sign ($).
-}
isDollar :: Char -> Bool
isDollar character = _YOUR_CODE_HERE
{-
Exercise:
Define an "exclusive or" function: http://en.wikipedia.org/wiki/Exclusive_or#Truth_table
You probably want to use the following functions:
(&&) :: Bool -> Bool -> Bool
(||) :: Bool -> Bool -> Bool
-}
xor :: Bool -> Bool -> Bool
xor arg1 arg2 = _YOUR_CODE_HERE