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Today's Topics:
1. Unsubscribe (Christopher Ledbetter)
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Message: 1
Date: Mon, 27 Apr 2020 08:08:45 -0400
From: Christopher Ledbetter <cledbett...@yahoo.com>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <beginners@haskell.org>
Subject: [Haskell-beginners] Unsubscribe
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> On Apr 26, 2020, at 8:51 AM, Ken Overton <ken.over...@gmail.com> wrote:
>
>
> Hello all,
>
> I recently came across this function which made me realize I don't understand
> list comprehensions well. I hope someone can help me understand them better
> by understanding this example better. The function takes a list of Eq and
> returns the list of unique elements from it:
>
> unique :: Eq a => [a] -> [a]
> unique xs = [x | (x,y) <- zip xs [0..], x `notElem` (take y xs)]
>
> It's using a list comprehension with multiple 'generators' (hope I have the
> term correctly). My understanding of multiple generators in a list
> comprehension is that they refine the results of the previous generator.
>
> So the first generator should produce [(Eq,Int)] as input to the second
> generator? And the second generator should produce [Bool]?
>
> My understanding must be wrong though; how do we end up with just the items
> where the second generator produced True?
>
> Thanks,
>
>
> --
> Ken Overton
> (917) 863-3937
> ken.over...@gmail.com
>
> _______________________________________________
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> Beginners@haskell.org
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