What is the problem that these new sigils attempt to solve? They're just a
few characters away from .parse/1. Is the intention here to change the
implementation of the inspect protocol, like so:
iex> Version.parse!("0.0.1")
~Version<0.0.1>
If yes, then it looks like a great change. Otherwise I don't see the
benefits.
Best,
Stefan
niedz., 16 lut 2020 o 16:07 José Valim <[email protected]> napisał(a):
> Fernando, yes. The reason I like this proposal is exactly because it
> steers multi-letter sigils away from aliases - which we have tried before
> and it introduced a bunch of separate issues with them.
>
> On Sun, Feb 16, 2020 at 2:57 PM Fernando Tapia Rico <[email protected]>
> wrote:
>
>> (Related to Allen's comment)
>>
>> Sigils would be independent of aliases, right?
>>
>> For example, if Decimal provides sigil_Decimal and an alias is defined
>> as alias Decimal, as: D then the sigil would still be used as
>> ~Decimal<...> and not ~D<...>.
>>
>> On Saturday, February 15, 2020 at 10:34:01 PM UTC+1, Bruce Tate wrote:
>>>
>>> I love this proposal. It takes a construct that was formerly limited and
>>> opens it up with very little cost in readability.
>>>
>>> -bt
>>>
>>> On Sat, Feb 15, 2020 at 4:04 PM Allen Madsen <[email protected]>
>>> wrote:
>>>
>>>> +1
>>>>
>>>> I think if sigil names with dots is allowed, it should be based on the
>>>> fully qualified name of the module the sigil is defined in or it's alias.
>>>> For example:
>>>>
>>>> module Date
>>>> defmacro sigil_Range(range, _flags) do
>>>> #...
>>>> end
>>>> end
>>>>
>>>> require Date
>>>> alias Date, as: D
>>>> ~Date.Range<...>
>>>> ~D.Range<...>
>>>>
>>>> Allen Madsen
>>>> http://www.allenmadsen.com
>>>>
>>>>
>>>> On Sat, Feb 15, 2020 at 10:11 AM José Valim <[email protected]>
>>>> wrote:
>>>>
>>>>> I believe this is the best proposal on the topic so far. I agree with
>>>>> trade-offs too (disclaimer: we have talked about those trade-offs
>>>>> privately
>>>>> before). I would suggest two amendments:
>>>>>
>>>>> 1. Limit multi-letter sigils only to uppercase sigils for now
>>>>> 2. Include "only: :sigils" as part of the initial implementation
>>>>>
>>>>>
>>>>> On Sat, Feb 15, 2020 at 2:52 PM Wojtek Mach <[email protected]>
>>>>> wrote:
>>>>>
>>>>>> Currently sigils are single letter which means there can be only 2 x
>>>>>> 26 of them and some of them
>>>>>> are already taken by the standard library. As mentioned in [1] it's
>>>>>> not clear if there should be
>>>>>> for example a `~P` and if so, whether it should be for PID or Port.
>>>>>> Similarly, there couldn't be an
>>>>>> `~R` sigil for Reference given the symbol is already taken by Regex.
>>>>>>
>>>>>> I'd like to propose to extend sigils to support multiple letters. For
>>>>>> example, to define a
>>>>>> `~Port` sigil we'd write a `sigil_Port` function/macro and to use it
>>>>>> it would have to be either
>>>>>> local to the module or be imported. After the first letter, we could
>>>>>> only use US-ASCII letters
>>>>>> (a-z, A-Z). If a sigil starts with a lower-case letter it's
>>>>>> interpolated, otherwise it is not.
>>>>>>
>>>>>> As part of this proposal I'd like to introduce the following sigils
>>>>>> to the Kernel module:
>>>>>>
>>>>>> - `~Port<0.6>`
>>>>>> - `~PID<0.108.0>`
>>>>>> - `~Reference<0.2489367154.3551002625.84263>`
>>>>>> - `~Version<1.0.0>`
>>>>>> - `~URI<https://elixir-lang.org>`
>>>>>>
>>>>>> But worth mentioning that the primary goal of this proposal is allow
>>>>>> the community to build sigils
>>>>>> like these:
>>>>>>
>>>>>> - `~Decimal<3.14>`
>>>>>> - `~Complex<0+1i>`
>>>>>> - `~Ratio<1/3>`
>>>>>> - `~Money<100 USD>`
>>>>>> - `~Geo<SRID=4326;POINT(30 -90)>`
>>>>>> etc
>>>>>>
>>>>>> basically whenever there's some piece of structured data with compact
>>>>>> string representation it'd
>>>>>> be a good candidate for a sigil.
>>>>>>
>>>>>> Notice, I have chosen the same delimiter, `<`, for all proposed
>>>>>> sigils. Different ones for
>>>>>> different sigils could be of course chosen as the "cannonical"
>>>>>> (returned from the Inspect
>>>>>> implementation.)
>>>>>>
>>>>>> Below I'd like to discuss some limitations of this proposal.
>>>>>>
>>>>>> Given we already have sigils that correspond to structs like `~D`,
>>>>>> `~T`, `~N`, `~U`, `~R`, should
>>>>>> we deprecate them in favour of `~Date`, `~Time`, `~NaiveDateTime`,
>>>>>> `~DateTime`, `~Regex`? I'd
>>>>>> arbitrarily say we **should not** and instead keep them as is.
>>>>>> (Personally I wouldn't mind using
>>>>>> all of these except for maybe `~NaiveDateTime` which is rather long.)
>>>>>>
>>>>>> The longest possible sigil name would be 249 letters (which along
>>>>>> with 6 letters in `sigil_` make
>>>>>> 255 characters which is the atom length limit). A shorter maximum
>>>>>> name length could be chosen.
>>>>>>
>>>>>> As mentioned in [2], we run into technical limitations when
>>>>>> implementing a ~MapSet sigil, given
>>>>>> sigils work on string and not the AST. This could be emulated with
>>>>>> some caveats [3]. I'd argue
>>>>>> that given single letter sigils have exactly the same problem,
>>>>>> perhaps it's not a deal-breaker,
>>>>>> just one of consequence of the original design.
>>>>>>
>>>>>> Given multi-letter sigils may (but of course don't have to)
>>>>>> correspond to module names, what about
>>>>>> modules with dots like `Date.Range` and `Version.Requirement`? This
>>>>>> is especially relevant for
>>>>>> user provided sigils, e.g. `~MyApp.Money`. Turns out it's very easy
>>>>>> to support these too, instead
>>>>>> of `def sigil_Date.Range` which would be a syntax error, we would do
>>>>>> `def
>>>>>> unquote(:"sigil_Date.Range")`. But then the other parts of the system
>>>>>> don't quite work either,
>>>>>> e.g. instead of `iex> h sigil_Date.Range` currently we would have to
>>>>>> do
>>>>>> `iex> h Kernel."sigil_Date.Range"`. For what it's worth it's not very
>>>>>> different than the `./2`
>>>>>> macro [4] which has similar caveats. In any case, as much as I'd
>>>>>> personally like to see
>>>>>> `~Date.Range` in particular, I concede we probably should stick to
>>>>>> just supporting letters for
>>>>>> now.
>>>>>>
>>>>>> Worth mentioning that sigils need to be manually imported into the
>>>>>> current scope (unless they are
>>>>>> already there by default, like the ones on Kernel). Thus, to use
>>>>>> ~Decimal, users would have to do:
>>>>>> `import Decimal, only: [sigil_Decimal: 2]`. A convenience like
>>>>>> `import Decimal, only: :sigils`
>>>>>> could be added in the future but it's not the topic of this proposal.
>>>>>>
>>>>>> Limitations aside, here's a proof-of-concept!
>>>>>>
>>>>>> https://github.com/elixir-lang/elixir/compare/master...wojtekmach:wm-long-sigil
>>>>>>
>>>>>> - [1]
>>>>>> https://groups.google.com/forum/#!topic/elixir-lang-core/C7-QgKKu1Mw,
>>>>>> - [2]
>>>>>> https://github.com/elixir-lang/elixir/pull/9640#issuecomment-564022856
>>>>>> - [3]
>>>>>> https://gist.github.com/wojtekmach/7d4b5dc2f45a4708ce04d19e7c381360
>>>>>> - [4]
>>>>>> https://github.com/elixir-lang/elixir/blob/v1.10.1/lib/elixir/lib/kernel/special_forms.ex#L492
>>>>>>
>>>>>> --
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>>>>>> send an email to [email protected].
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>>>>>> https://groups.google.com/d/msgid/elixir-lang-core/E4F9858D-7019-4E2E-A463-9FEDAFA52B0E%40wojtekmach.pl
>>>>>> .
>>>>>>
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>>>>
>>>
>>>
>>> --
>>>
>>> Regards,
>>> Bruce Tate
>>> CEO
>>>
>>>
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>>>
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