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Contents
module FoodChain (song) where
import Data.Array (Array, Ix, (!), listArray)
import Data.Char (toLower)
import Text.Printf (printf)
data Animal = Fly | Spider | Bird | Cat | Dog | Goat | Cow | Horse
deriving (Eq, Enum, Ix, Ord, Show)
-- | An array that contains the lowercase string representation for all
-- animals. E.g. animalNames ! Fly == "fly"
animalNames :: Array Animal String
animalNames = listArray (Fly, Horse) $ map showLower [Fly ..]
where showLower a = let (h:t) = show a
in (toLower h : t)
song :: String
song = init . unlines $ map verse [Fly ..]
verse :: Animal -> String
verse animal = swallow animal ++ unlines (map catches prey)
where prey | animal `elem` [Fly, Horse] = []
| otherwise = [animal, pred animal .. Spider]
swallow :: Animal -> String
swallow animal = printf "I know an old lady who swallowed a %s.\n%s\n"
(animalNames ! animal) (comment animal)
catches :: Animal -> String
catches animal = printf "She swallowed the %s to catch the %s%s"
(animalNames ! animal) (animalNames ! prev) (end prev)
where prev = pred animal
end Fly = ".\n" ++ comment Fly
end Spider = " that wriggled and jiggled and tickled inside her."
end _ = "."
comment :: Animal -> String
comment animal = case animal of
Fly -> "I don't know why she swallowed the fly. Perhaps she'll die."
Spider -> "It wriggled and jiggled and tickled inside her."
Bird -> "How absurd to swallow a bird!"
Cat -> "Imagine that, to swallow a cat!"
Dog -> "What a hog, to swallow a dog!"
Goat -> "Just opened her throat and swallowed a goat!"
Cow -> "I don't know how she swallowed a cow!"
Horse -> "She's dead, of course!"
Version data entries
302 entries across 302 versions & 1 rubygems