[Haskell-cafe] Preferred syntax for append

[Hécate]

Hi Mark,

Yes I would favour Rebecca's approach in her book to use Semigroup. 
Personally I never think of lists as Monads, as I see this instance 
useful only to power list comprehension.

Concatenation with (<>) is more meaningful and holds better semantics 
than (<|>), described as just "An associative binary operation".  It's 
so vague it could be the documentation for a Magma typeclass, and the 
name "Alternative" is quite loaded (we think especially of parsers when 
thinking/seeing Alternative).

Cheers,

Hécate

Le 12/05/2024 à 21:41, Mark McConnell via Haskell-Cafe a écrit :
> We know that lists have map.  Sometimes we want to take the higher 
> perspective of Functor, replacing map with fmap, then replacing fmap 
> with <$> .  This post asks the corresponding question about append.
>
> The notation for append within List itself is ++ .  Often we think of 
> lists as Monads.  Applicative generalizes Monad, and Alternative 
> specializes Applicative.  Alternative has <|> which behaves as ++ on 
> List.  I have been using <|> for this purpose.
>
> Recently, I have begun to read and enjoy "Effective Haskell".  In 
> Chapter 1, this book uses <> for append.  Clearly they are thinking of 
> List as a Semigroup.
>
> I'm curious about your thoughts on ++ versus <|> versus <> .
>
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