I don't think it's really so great that Data.List has a bunch of operations that are inefficient on lists.

On Wed, Oct 31, 2018, 10:53 PM Dannyu NDos <ndospark320@gmail.com wrote:

I've suffered from inconvenience due to the restricted type signature. I'll be very glad if such restrictions are lifted:

deleteBy :: (a -> b -> Bool) -> a -> [b] -> [b]

deleteFirstsBy :: (a -> b -> Bool) -> [a] -> [b] -> [b]

intersectBy :: (a -> b -> Bool) -> [a] -> [b] -> [a]

I approve these versions because:

1. It makes more sense that the "usual" `delete` and `intersect` functions are specialization of the "By" operations, not the vice versa.

2. Data.Map.Lazy module from containers package has these kind of "By" operations.

The previous discussion about this in Sep 2016 didn't make much conclusion, so let the discussion continue.

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