Units.hs

module Units where

data Feel = VeryCold | Cold | Nice | Hot | VeryHot deriving (Show, Eq, Ord)
data Temp = C Float | F Float | K Float deriving (Show, Eq)

-- Define C <-> F
ftoc (F t) = C $ (t -  32) * 5/9
ctof (C t) = F $ (t * 9/5) + 32

-- Define C <-> K
ctok (C t) = K $ t + 273.15
ktoc (K t) = C $ t - 273.15

-- Define F <-> K  with F <-> C <-> K
ftok = ctok . ftoc
ktof = ctof . ktoc

-- Boiling
isFreezing :: Temp -> Bool
isFreezing (F t) | t <= 32    = True
				| otherwise  = False

isFreezing (C t) = isFreezing . ctof $ (C t)
isFreezing (K t) = isFreezing . ktof $ (K t)

-- Freezing
isBoiling :: Temp -> Bool
isBoiling (F t) | t >= 212    = True
				| otherwise  = False

isBoiling (C t) = isBoiling . ctof $ (C t)
isBoiling (K t) = isBoiling . ktof $ (K t)

(∈) x [u,v] = x >= u && x <= v

-- Heat Index 
-- Being good Californians, we're using Faranheit as a rubric

feeling :: Temp -> Feel
feeling (F t) | t < 64         = VeryCold
			  | t < 70         = Cold
              | t ∈ [70, 79]   = Nice
              | t > 100        = VeryHot
              | t > 79         = Hot

feeling (C t) = feeling . ctof $ C t
feeling (K t) = feeling . ktof $ K t