[Haskell-cafe] How to write fast for loops

[Niklas Hambüchen]

On 27/04/14 03:28, John Lato wrote:
> No, I mean this:
> 
>> V.forM_ (V.enumFromN 1 n)

Hey John,

unfortunately that's not fast, and it eats all the RAMs.

Here comes the sad comparison of looping in Haskell:

- loop (maxBound :: Word32)
  3 seconds, constant space

- forM_ [0..maxBound :: Word32]
  36 seconds, constant space

- V.forM_ (V.enumFromTo 0 (maxBound :: Word32))
  37 seconds, constant space

- V.forM_ (V.enumFromN 0 (fromIntegral (maxBound :: Word32)))
  linear space -> crashes

All loops execute `return ()`.

:(