[Haskell-cafe] Preferred syntax for append

[Mark McConnell]

 Thanks to all who replied.   I will be changing <|> to <> .
    On Monday, May 13, 2024 at 03:05:48 AM EDT, Hécate via Haskell-Cafe <haskell-cafe at haskell.org> wrote:  
 
  
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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Hécate ✨
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