[Haskell-cafe] Function application layout

[Alexander Solla]

2011/5/25 Jonas Almström Duregård <jonas.duregard at chalmers.se>

> Hi Alexander,
>
>
> > This is "exactly" the applicative style, where idiom brackets come from.
>
> I disagree. Layout has at least two advantages over applicative here:
>
> 1) Applicative costs (at least) three additional characters per function
> parameter.
>

I don't think so.  Presumably, you would replace them with spaces, if you
were indenting to "tabular" form.


> 2) You can not have arbitrary infix operators in the parameters when using
> applicative.


True.


>


> Also your example is not really equivalent to f (x a) (y b) (z c) is it?


It is up to isomorphism, if you use the identity functor:

newtype Id a = Id { unId :: a }

tryItOut :: Id Int
tryItOut = (+) <$> 1 <*> 2



>
>
> > Idiom brackets abstract the <$> (fmap) and (<*>) operators away.
>
> But from what I can tell it also reintroduces the parenthesis? How would
> you write f (x a) (y b) in idiom brackets?
>

I prefer the applicative style, so I would use that.

>
> /J
>
>
> On 25 May 2011 22:06, Alexander Solla <alex.solla at gmail.com> wrote:
> >
> >
> > 2011/5/25 Jonas Almström Duregård <jonas.duregard at chalmers.se>
> >>
> >> I don't see the similarity (from reading this:
> >> http://www.haskell.org/haskellwiki/Idiom_brackets). My suggestion is
> >> just a way of using layout to avoid parenthesis.
> >>
> >
> > This is "exactly" the applicative style, where idiom brackets come from.
> >  Use Control.Applicative:
> > f <$> x a
> >   <*> y b
> >   <*> z c
> > You can use the identity functor to recover "plain old" function
> > application.  Idiom brackets abstract the <$> (fmap) and (<*>) operators
> > away.
> > And yes, you are right that applicative style is very useful.
>
>
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