Hi Cafe,

I was coding this morning when I suddenly found something that surprised me. It's been a short time since I am really caring about the performance of my programs. Before, I was just caring about their correctness. So I am trying different things and profiling to see differences. One difference I have found surprising is that the function f is MUCH faster and less space consuming than the function g:

import Control.Monad

import qualified Data.Sequence as Seq

type Seq = Seq.Seq

f :: Monad m => Int -> m a -> m (Seq a)
f n = fmap Seq.fromList . replicateM n

g :: Monad m => Int -> m a -> m (Seq a)

g = Seq.replicateM

Maybe is just in my test case, where the Int argument is big and the monadic action short, but it looks to me that Data.Sequence.replicateM can be faster than it is right now.

Regards,

Daniel Díaz.

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let f x = x in x