[Haskell-cafe] Is there a library that has a strict version of `sum`?

Matt parsonsmatt at gmail.com
Tue Aug 14 19:22:44 UTC 2018

`foldr (+) 0` is going to create a bunch of thunks replacing the spine of
the list. This is desirable if the number type can take advantage of
laziness in some way (eg a `data Nat = Z | Succ Nat`), but for most cases,
the `foldl' (+) 0` implementation is preferable.

`sum' = foldl' (+) 0` would (in my opinion) be a reasonable addition to the
Prelude, or at least Data.Foldable, but no one has done the work to do that
-- if you raise an issue on the GHC Trac then it will be up for discussion
and possible inclusion.

Matt Parsons

On Tue, Aug 14, 2018 at 1:17 PM, Imants Cekusins <imantc at gmail.com> wrote:

> >  I have to sum up values in different lists, and as soon as I try this
> with large lists the memory usage blows up.
> did you try splitting the list in chunks and summing those chunks?
> there is this chunksOf function:
> http://hackage.haskell.org/package/containers-
> docs/Data-Sequence.html#g:9
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