CODEWITHSUNDEEP
haskell
04k
04k

Reputation: 53

Haskell Function not accepting argument

I wrote a simple code to convert rgb to cmyk. Then I defined the datatype Color. now I got this error:

Couldn't match expectet type `Color' with actual type `(t0, t1, t2)'

I thought Color would refer to Rgb(Int,Int,Int). What I have done wrong?

My code:

data Color = Rgb (Int,Int,Int) | Cmyk Double Double Double Double deriving (Show)

rgb2cmyk :: Color -> Color
rgb2cmyk (Rgb (0,0,0)) = (Cmyk 0 0 0 1)
rgb2cmyk (Rgb (r,g,b)) = (Cmyk c m y k)
    where 
            rd = (fromIntegral r)/255
            gd = (fromIntegral g)/255
            bd = (fromIntegral b)/255
            w = max3 rd gd bd
            c = w - rd/w
            m = w - gd/w
            y = w - bd/w
            k = 1 - w

max3 :: Double -> Double -> Double -> Double
max3 a b c  | a>=b && a>=c  = a
            | b>=a && b>=c  = b
            | otherwise     = c

test1 = rgb2cmyk 233 123 123

Error occours in test1 line. Do I have to write rgb2cmyk $ Rgb?

Upvotes: 2

Views: 106

Answers (1)

Netwave
Netwave

Reputation: 42786

I would suggest to keep the syntax, keep Rgb Int Int Int instead of Rgb (Int,Int,Int)

data Color = Rgb Int Int Int | Cmyk Double Double Double Double deriving (Show)

rgb2cmyk :: Color -> Color
rgb2cmyk (Rgb 0 0 0) = (Cmyk 0 0 0 1)
rgb2cmyk (Rgb r g b) = (Cmyk c m y k)
    where 
    (...)


*Main> rgb2cmyk $ Rgb 0 0 0
Cmyk 0.0 0.0 0.0 1.0

Explaining the comment:

You cant call rgb2cmyk as rgb2cmyk x y z, the function is expecting an Rgb x y z so you must call it as rgb2cmyk Rgb 10 10 10 for example. Rgb is a Color is a constructor and either Rgb or Cmyk must be called if your function takes a Color.

Upvotes: 2

Related Questions