Index-based access on a list is very frequently an anti-pattern. Allowing
list[i] means it will be easier to write non-efficient versions of
algorithms without a second thought for those coming from imperative
languages, instead of using the functions in Enum. It means someone can
write this:
for i <- 0..length(list)-1 do
list[i] * 2
end
We should not make it easy to write non-idiomatic code.
If we want to allow this syntax then I would like to see a comprehensive
list of examples where accessing a list by index is important and doing so
via the bracket syntax is important enough to justify it.
On Thu, Sep 21, 2023 at 6:23 PM Zach Daniel <zachary.s.dan...@gmail.com>
wrote:
> Right now if you use access on a list, it expects it to be a keyword and
> requires the value to be an atom.
>
> I've tried to think of a reason why we couldn't support this in the
> language, but I haven't been able to. If the value being accessed is an
> `integer` it could get the item at that index, and if its an `atom` it
> could treat it as a keyword and get the value for that key.
>
> `[1, 2, 3][0] -> 1`
> `[foo: :bar][0] -> {:foo, :bar}`
> `[foo: :bar][:foo] -> :bar`
> `[1, 2, 3][:foo] -> not a keyword list error`
>
> It was pointed out that perhaps we don't do this to express that indexing
> a list is not fast in Elixir like it is in other languages, but I'm not
> sure if that is sufficient reason IMO to leave out a typically very
> standard feature of lists.
>
> Thoughts?
>
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