What is the leak of space?

Question

I found a haskell wiki page on space leaks that claims to list examples of real leaks that aren't there. In fact, he does not say what a leak of space is; it simply links to a page for memory leaks.

What is the leak of space?

Answer 1

As @Rasko noted in the answer, a space leak refers to a situation where a program or a particular calculation uses more (usually much more) memory than is necessary for the calculation and / or expected by the programmer.

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main = print $ sum [1..1000000000]

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main = let vals = [1..1000000000]
       in print (sum vals, length vals)

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main = do txt <- getContents
          print (length txt, length (words txt))

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main = do txt <- getContents
          print $ length txt

main = do txt <- getContents
          print $ length (words txt)

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{-# LANGUAGE BangPatterns #-}

import Data.List
import Data.Char

charsWords :: String -> (Int, Int)
charsWords str = let (_, chrs, wrds) = foldl' step (False, 0, 0) str
                 in (chrs, wrds)
  where step (inWord, cs, ws) c =
          let !cs' = succ cs
              !ws' = if not inWord && inWord' then succ ws else ws
              !inWord' = not (isSpace c)
          in (inWord', cs', ws')

main = do txt <- getContents
          print $ charsWords txt

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Answer 2

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