Execute HQ9+/Haskell
This HQ9+ interpreter is written in Haskell. We use mapAccumR to maintain the accumulator. However, the specification doesn't say what to do with said accumulator on completion.
Execute HQ9+/Haskell is an implementation of HQ9+.
Other implementations of HQ9+.
Execute HQ9+/Haskell is part of RCHQ9+. You may find other members of RCHQ9+ at Category:RCHQ9+.
module Main where
import Data.Char (toLower, toUpper)
import Data.List -- for concat
import Data.Traversable -- for mapAccumR
main :: IO ()
main = do
s <- getLine
putStrLn (snd (hq9p s))
hq9p :: String -> (Int,String)
hq9p src = fin $ mapAccumR run 0 $ map toLower src
where
fin (acc,log) = (acc,concat log)
run acc ch = case ch of
'h' -> (acc,"Hello, world!")
'q' -> (acc,src)
'9' -> (acc,bottles)
'+' -> (acc + 1,"")
'_' -> (acc,"")
bottles :: String
bottles = [99, 98 .. 0] >>= beers
where
beers n = unlines [
bob n ++ " on the wall, " ++ bob n ++ ".",
pass n ++ bob (n - 1) ++ " on the wall.\n"]
bob n =
let nu = case n of { (-1) -> "99"; 0 -> "No more"; n -> show n; }
s = if n == 1 then "" else "s"
in nu ++ " bottle" ++ s ++ " of beer"
pass n = case n of
0 -> "Go to the store and buy some more, "
_ -> "Take one down and pass it around, "