[Joker_vD]

    let nums = take 10000000 naturals
    print $ (sum nums, length nums)

> Because the nums list is used for both sum and length computations, the compiler can’t discard list elements until it evaluates both.

Now that makes me wonder, if I write something like

    print $ (sum (take 10000000 naturals), length (take 10000000 naturals))

will it run in constant memory? I think it ought to, but are there mechanisms in GHC optimizer to prevent extraction of CSEs that would cause huge increases in memory consumption?

[endgame]

The solution to this is a package like https://hackage.haskell.org/package/foldl , which lets you fuse multiple traversals of a lazy list into a single pass and get the laziness right.

[hgsgm]

It's both solvable and easy to accidentally have blowups by accident.

[sbergot]

yeah sadly this summarize my haskell experience. I would hate to do code reviews in haskell.