Should foldl' be added to the post-"Plan FTP" Prelude

David Feuer david.feuer at
Sun Mar 8 04:33:13 UTC 2015

On Sat, Mar 7, 2015 at 6:08 PM, Ben Franksen <ben.franksen at> wrote:
> David Feuer wrote:
>> FTP sets up the expectation that foldl has a specific relationship to
>> foldMap.
> How does foldl have a more specific relationship with foldMap than foldl'?
> Both are currently methods of class Foldable, BTW.

Yes, and each is expected to have a specific relationship to foldMap.
Changing the foldl for lists breaks that.


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