Data.Foldable.foldr1 too strict

[Ian Lynagh]

On Thu, Sep 27, 2012 at 05:36:00PM +0200, Bertram Felgenhauer wrote:
> 
> But we could define
> 
>   foldr1 f (x:xs) = foldr f x xs
> 
> which would be more lazy. I see no advantage to defining foldr1 as
> in the standard library, am I missing anything?

That doesn't have the right behaviour:

Prelude> Data.List.foldr1 (-) [3,5]
-2
Prelude> let foldr1 f (x:xs) = foldr f x xs in foldr1 (-) [3,5]
2


Thanks
Ian