Old lady swallowed a fly: Difference between revisions

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=={{header|Haskell}}==
=={{header|Haskell}}==


⚫
<lang haskell>import Data.List
{{Works with|GHC|7.8.3}}


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animals=
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<lang haskell>import Data.List (tails)
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["fly.\nI don't know why she swallowed a fly.\nPerhaps she'll die.\n"
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,"spider.\nThat wiggled and jiggled and tickled inside her."
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,"bird.\t\nHow absurd, to swallow a bird."
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,"cat.\t\nImagine that. She swallowed a cat."
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,"dog.\t\nWhat a hog to swallow a dog."
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,"goat.\t\nShe just opened her throat and swallowed that goat."
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,"cow.\nI don't know how she swallowed that cow."
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,"horse.\nShe's dead, of course."]


⚫
beginnings = map ("There was an old lady who swallowed a "++) animals
-- Once means the phrase is only printed in the verse about that animal.
⚫
swalloed x y = "She swallowed the "++takeWhile (/='.') y++" to catch the "++ takeWhile (/='\t') x
-- Every means the phrase is printed for every verse. It is used for "fly",
lastVerse = tail $ reverse $ zipWith swalloed animals $ tail animals
-- and could optionally be used for "spider", in the version of the song where
main = putStr $ concatMap unlines $ zipWith (:) beginnings $ cycle $ reverse $ tails $ lastVerse</lang>
-- "wriggled and jiggled..." is repeated every verse.
-- Die is only used for the horse, and means the chain of animals won't be
-- included in the verse.
data AnimalAction
= Once
| Every
| Die

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animals =
⚫
[ ("horse", Die, "She's dead, of course!")
, ("donkey", Once, "It was rather wonky. To swallow a donkey.")
⚫
, ("cow", Once, "I don't know how. To swallow a cow.")
⚫
, ("goat", Once, "She just opened her throat. To swallow a goat.")
, ("pig", Once, "Her mouth was so big. To swallow a pig.")
⚫
, ("dog", Once, "What a hog. To swallow a dog.")
⚫
, ("cat", Once, "Fancy that. To swallow a cat.")
⚫
, ("bird", Once, "Quite absurd. To swallow a bird.")
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, ("spider", Once, "That wriggled and jiggled and tickled inside her.")
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, ("fly", Every, "I don't know why she swallowed the fly.")
]

verse :: [(String, AnimalAction, String)] -> [String]
verse ((anim, act, phrase):restAnims) =
⚫
let lns = ["I know an old lady who swallowed a " ++ anim ++ ".", phrase]
in case act of
Die -> lns
_ -> lns ++ verse' restAnims anim

verse' :: [(String, AnimalAction, String)] -> String -> [String]
verse' [] _ = ["Perhaps she'll die."]
verse' ((anim, act, phrase):restAnims) prevAnim =
⚫
let why = "She swallowed the " ++ prevAnim ++ " to catch the " ++ anim ++ "."
lns =
case act of
Every -> [why, phrase]
_ -> [why]
in lns ++ verse' restAnims anim

song :: [String]
song = concatMap verse . tail . reverse $ tails animals

main :: IO ()
main = putStr $ unlines song</lang>


=={{header|Icon}} and {{header|Unicon}}==
=={{header|Icon}} and {{header|Unicon}}==
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