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

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.

I suppose you could go against that,

I have not yet formed an opinion. I just want to understand your response which remains cryptic to me.

and also break any code relying on the current foldl semantics, but I'd personally be very much opposed to that.

Fair enough, but a different matter. Cheers Ben

On Mar 1, 2015 5:13 PM, "Ben Franksen" wrote:

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Why not?

David Feuer wrote:

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No, that is not a way now that we have FTP.

On Wed, Feb 25, 2015 at 7:31 PM, Kazu Yamamoto wrote:

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I would love to have foldl' as part of the Prelude. I use it quite frequently and it seems like a beginner trap to have foldl but not foldl' (which is almost always the better choice). I see that foldMap has been added (in addition to all of Monoid and Traversable), why was foldl' left out?

That is one way but I think another way is to make foldl strict:

http://www.well-typed.com/blog/90/

I'm tired of explaining the difference of foldl and foldl' to beginners. :-)

--Kazu