Proposal: Dot as Postfix Function Apply

[Edward Kmett]

Precedence and syntax in a language tells you a lot about what the language
considers important. We take the 'quietest' syntax for things that we want
to have fade into the background. Whitespace and periods are both very
quiet syntax.

In math ' ' is often multiplication, in the lambda calculus it is function
application.

We choose ' ' to have the tightest precedence in Haskell in a way that
nicely emphasizes the importance of functions here. Admittedly we already
have two awkward exceptions there that routinely throw folks for loops. @
syntax in patterns and the {}'s used by record syntax both bind tighter
than whitespace application.

We choose . for function composition a.) because it on the keyboard and
again, it emphasizes the importance of functions. Functions compose and you
can make more interesting things out of the parts, the field accessor
syntax you propose here does not compose particularly well.

With other solutions available today that this proposal actively makes
worse, I can both read and write back to those fields

You're asking for (.), one of the most common symbols in Haskell code today
to take on another meaning, furthering confusion for its current standard
role, for it to effectively alternate binding looser than ' ' when you put
spaces around it to tighter than ' ' when you don't while simultaneously
changing semantics entirely.

Is it confusing to newcomers that (.) doesn't bind tighter than ' ' in
haskell? Sure. But causing that to randomly change back and forth is more
confusing still.

-Edward

On Wed, Nov 4, 2015 at 2:40 PM, Harry . <voldermort at hotmail.com> wrote:

> When you consider that every other programming language in common use (and
> almost every language not in common use as well) allows you to write:
>
> print person.name
>
> while Haskell requires something like:
>
> print (person & name) or
>
> print $ person.^name
>
> and even that after importing a third-party library or defining it
> yourself, you begin to understand why beginners think that Haskell looks
> more like Japanese emoticons than programming.
>
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