I believe that printing expressions is what python usually does in their
inspect implementation. It does help a lot with copy & paste when working with
the shell.
From: elixir-lang-core@googlegroups.com <elixir-lang-core@googlegroups.com> on
behalf of José Valim <jose.va...@dashbit.co>
Date: Monday, 7 February 2022 at 13:57
To: elixir-lang-core <elixir-lang-core@googlegroups.com>
Subject: Re: [elixir-core:10767] [Proposal] Update MapSets with pattern
matching, assignments, update shorthand, etc.
And for all of those cases, if we the concern is inspections, there is always
the option of printing an expression, such as:
MapSet.new([1, 2, 3])
URI.parse("https://foo/bar";)
Version.parse!("1.0.0")
It doesn't address the concerns about pattern matching though.
On Mon, Feb 7, 2022 at 2:31 PM Wojtek Mach
<woj...@wojtekmach.pl<mailto:woj...@wojtekmach.pl>> wrote:
Regarding `%MapSet[1, 2]`, I think it looks really nice.
Regarding multi-letter sigils, I think we should have those but not for this
particular use case. Sigils are for textual representations so not a good fit
for "containers" like MapSet, Vector, etc, when evaluating `%MapSet[...]` we
want to evaluate the items inside as _code_ not as _text_ (which the sigil
would). There's also the sigil escaping that José mentioned.
This begs the question do we have `%MapSet[1, 2]` AND `~Version[1.0.0]` and I'd
say YES but I totally can see why they maybe look a bit too similar with pretty
different semantics and thus it's one or the other (or none!)
Regarding the gist,
iex> enum = [:foo, :bar, "set"]
...> %[enum]
%[:foo, :bar, "set"]
I think this should be `%[[:foo, :bar, "set"]]`. :) Otherwise `%[x]` is
different than `%[x, y]` which feels unpredictable.
def function_2(%[:foo])
what are semantics of this pattern match? Does it match when the given set is:
1. a subset of `%[:foo]`
2. when it is exactly the same?
# Match and update - like `%{map | key: new_val}`
iex> set = %[%User{id: 1}]
iex> %[set | %User{} => %User{id: 2}]
note, on maps we cannot do `%{map | %User{} => %User{id: 2}}` today. I mean, we
can, but it doesn't do what you want it to do, it would try to update a key
that `%User{}` evaluates to, something like `%User{id: nil, ...}`. Changing the
semantics would be a breaking change. It's unclear how it should work when it
matches multiple elements, do we update all of them? That's not obvious!
On February 7, 2022, "a-corp.co.uk<http://a-corp.co.uk>"
<a...@a-corp.co.uk<mailto:a...@a-corp.co.uk>> wrote:
This is tricky for me. While I am sympathetic to the feature, I think this
would be the first time abstraction was added to pattern matching so we'd need
to be careful.
Up to now the pattern matching syntax uses the same syntax that you use to
create the literal data that is being matched. Eg for a map pattern we write a
map
%{a: variable} = %{a: 1}
This brings clarity because the pattern describes the data you are matching on
- when you read the pattern you can see right away what the expected data is (a
map).
The proposal sketched in the Gist would add indirection to pattern matching by
introducing a new syntax - syntax that is specific to one abstract data
structure (the map set).
By abstracting away the details of the data structure being matched on we
reduce the clarity we usually get, we introduce more syntax into the language,
and we open the floodgates
to whether we should have pattern matching on more abstract data types -
Ranges, URIs... DateTimes etc. At which point the question really becomes
"should we have abstract patterns
in Elixir" which I think is harder to answer.
In the meantime looking at ex_pat might be valuable to you because it would
allow you to reach into the details of a MapSet with pattern matching in a
controlled way that meant if the implementation
details of a MapSet changes it wouldn't break you program too much.
https://github.com/vic/expat
Just my two cents though!
Best
Adam
On 7 Feb 2022, at 10:33, SJ
<hellobenjamindank...@gmail.com<mailto:hellobenjamindank...@gmail.com>> wrote:
Hi all.
I have set out a proposal of what these things could potentially look like.
https://gist.github.com/bdanklin/f4fc015fa90e9b33bb8cb580344e1258
I searched for prior work in this area and couldn't find any.
If it's a welcome feature I'd be happy to work on it given some direction of
where to start.
Thanks for any feedback.
Best
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