> This was something I noticed that seemed inconsistent to me. If there's a
very good reason not to support it, that's fine.
The reason is that this is valid syntax on typespecs:
[kind: :unique | :duplicate, name: atom()]
[name: atom(), kind: :unique | :duplicate]
Generally speaking, changing operators precedence is going to backfire one
way or the other. :)
*José Valim*
www.plataformatec.com.br
Skype: jv.ptec
Founder and Director of R&D
On Fri, Sep 15, 2017 at 12:18 AM, Allen Madsen <[email protected]>
wrote:
> Sorry, I wasn't asking a question. I was making a proposal as it says in
> the title. Maybe the body of my message didn't convey that well or are you
> saying that proposals to change the language shouldn't be made on this
> mailing list?
>
> You're right that the current parsing of that statement does not make
> sense. I was suggesting instead of it being parsed like `[x: 1, y: (2 |
> [z: 3])]` it was parsed like `[{:x, 1}, {:y, 2} | [z: 3]]`.
>
> It is definitely true you can use the list concatenation operator to do
> what I'm suggesting, but that can have performance implications if the list
> on the left is large. The cons operator on the other hand is a constant
> time operation.
>
> This was something I noticed that seemed inconsistent to me. If there's a
> very good reason not to support it, that's fine.
>
>
> Allen Madsen
> http://www.allenmadsen.com
>
> On Thu, Sep 14, 2017 at 12:52 PM, Alexei Sholik <[email protected]>
> wrote:
>
>> Questions like this should be asked on the Elixir Forum.
>>
>> The problem with the expression `[x: 1, y: 2 | [z: 3]]` is that it is
>> parsed as `[x: 1, y: (2 | [z: 3])]`. As you may guess, the subexpression `2
>> | [z: 3]` does not make sense.
>>
>> There's actually a working way to build the keyword list you want: [x: 1,
>> y: 2] ++ [z: 3].
>>
>> On Wed, Sep 13, 2017 at 3:56 PM, Allen Madsen <[email protected]> wrote:
>>
>>> Yesterday I wrote code like the following:
>>>
>>> [x: 1, y: 2 | [z: 3]]
>>>
>>> I was really surprised when it didn't compile:
>>>
>>> ** (CompileError) iex:1: undefined function |/2
>>> (stdlib) lists.erl:1354: :lists.mapfoldl/3
>>> (stdlib) lists.erl:1355: :lists.mapfoldl/3
>>>
>>> The non-shorthand version works fine.
>>>
>>> [{:x, 1}, {:y, 2} | [z: 3]]
>>> #=> [x: 1, y: 2, z: 3]
>>>
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