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  1. import Control.Monad
  2.  
  3. import Data.Array.IO
  4.  
  5.  
  6. yoba :: Int -> IO Int  
  7. yoba n = do arr <- newArray_ (0, n) :: IO (IOUArray Int Int)
  8.             writeArray arr 0 0                                             
  9.             forM_ [1..n] (\v -> readArray arr (v - 1) >>= readArray arr >>= writeArray arr v . (v -))
  10.             readArray arr n
  11.  
  12. main = yoba 50000000 >>= print
stdin
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Standard input is empty
compilation info 
[1 of 1] Compiling Main             ( prog.hs, prog.o )
Linking prog ...
stdout
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30901700
https://ideone.com/9BiRW
language:
Haskell (ghc 8.4.4)
created:
14 years ago
visibility:
public

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