Pattern Matching

> let norm3D (x, y, z) = sqrt(x^2 + y^2 + z^2)
> 
> norm3D (33, 11, 3)
34.91418050019218
> 
> norm3D (33, 1, 3)
33.15116890850155
>

addVectors :: (Num a) => (a, a) -> (a, a) -> (a, a)
addVectors a b = (fst a + fst b, snd a + snd b)

> addVectors (8, 9)(-10, 12)
(-2,21)
> 
> addv1 = addVectors (1, 3)
> 
> let addv1 = addVectors (1, 3)
> 
> map addv1 [(12, 23), (45, 23), (6, 14)]
[(13,26),(46,26),(7,17)]

add3Dvectors (x1, y1, z1) (x2, y2, z2) = (x1+x2, y1+y2, z1+z
first  (x, _, _) = x
second (_, y, _) = y
third  (_, _, z) = z

> first (1, 2, 3)
1
> second  (1, 2, 3)
2
> third (1, 2, 3)
3   
> add3Dvectors (23, 12, 233) (10, 100, 30)
(33,112,263)

abs n | n >=0 = n
      | otherwise = -n

-- Without Pattern Matching
sign n = if n < 0 then - 1 else if n == 0 then 0 else 1


sign x | x >  0 =  1
       | x == 0 =  0 
       | x <  0 = -1

----------- OR -----


sign n | n <  0    = -1
       | n == 0    = 0
       | otherwise = 1


--------------------

> let sign x | x > 0 = 1 | x == 0 = 0 | x < 0 = -1


> map sign [-4..4]
[-1,-1,-1,-1,0,1,1,1,1]

f x y | y > z  = x^^2 - 10.5
      | y == z = x+10*y
      | y < z  = x/z + y
      where z = x^2 - 5*y

units angle sym | sym == "deg" = angle*pi/180.0
                | sym == "rad" = angle

> :{
| let units angle sym | sym == "deg" = angle*pi/180.0
|                 | sym == "rad" = angle
| 
| :}
> 
> units 180 "deg"
3.141592653589793
> 
> units pi "rad"
3.141592653589793
> 
> units 90 "deg" == pi/2
True
> 
> sin(units 90 "deg")
1.0
> sin(units 1.57 "rad")
0.9999996829318346
>

password :: (Eq a, Num a) => a -> [Char]
password 3423 = "OK - Safe opened"
password x    = "Error: Wrong Password pal"

> password 10
"Error: Wrong Password pal"
> password 11
"Error: Wrong Password pal"
> password 3423
"OK - Safe opened"
> s

sayMe :: (Integral a) => a -> [Char]
sayMe 1 = "One!"  
sayMe 2 = "Two!"  
sayMe 3 = "Three!"  
sayMe 4 = "Four!"  
sayMe 5 = "Five!"  
sayMe x = "Not between 1 and 5" 

> map sayMe [1..8]
["One!","Two!","Three!","Four!","Five!","Not between 1 and 5", "Not between 1 and 5","Not between 1 and 5"]