I support this feature. The arguments for
- a solution that composes well with pipes and
- the linters rejecting the most common solution of !!
are all particularly good ones. From my perspective, I teach composition
with pipes in the core, `with` in the boundary, and I try to have students
return a boolean rather than a truthy result as part of good API design.
The inability to convert from truthy to boolean has always felt like a
missing feature to me.
-bt
On Wed, Dec 23, 2020 at 10:42 AM Andrea Leopardi <an.leopa...@gmail.com>
wrote:
> What's the particular advantage of "to_boolean(term)" over "not
> is_nil(term)"? That it supports also booleans, which however could be used
> directly in predicates?
>
> Andrea
>
> On Wed, Dec 23, 2020 at 4:32 PM Moxley Stratton <moxley.strat...@gmail.com>
> wrote:
>
>> Here are examples:
>>
>> def has_access? do
>> at_least_logged_in? and !!get_csrf_cookie(session)
>> end
>>
>> %{event_form | submitted: !!event_form.submitted_at}
>>
>> case !!(membership_ends_on || trial_ends_on || dues_exempt) do
>> true -> changeset
>> false -> add_error(changeset, :membership_ends_on, "is required")
>> end
>>
>> case !!previous_value and !!new_value do
>> true -> put_change(changeset, :unconfirmed_email, new_value)
>> false -> changeset
>> end
>>
>> submitted? = !!Ecto.Changeset.get_change(changeset, :submitted_at)
>>
>> %{rsvpd: !!participation.rsvpd}
>>
>> On Tue, Dec 22, 2020 at 11:48 PM José Valim <jose.va...@dashbit.co>
>> wrote:
>>
>>> Can we revisit in which scenarios an explicit boolean conversion is
>>> necessary?
>>>
>>> On Wed, Dec 23, 2020 at 1:21 AM Moxley Stratton <
>>> moxley.strat...@gmail.com> wrote:
>>>
>>>> I would like revisit this issue.
>>>>
>>>> The issue was last discussed 5 years ago. Much has changed in that
>>>> time. The given solution was to use a double-negative (!!) to convert a
>>>> given value to a pure boolean.
>>>>
>>>> Here are the problems with the suggested solution:
>>>> 1. I believe this solution is a hack that is not intuitive to
>>>> beginners. It's rarely seen by mid and senior developers, meaning they have
>>>> to pause to interpret what !! means.
>>>> 2. A double negative can't be part of an Elixir pipeline.
>>>> 3. The Credo package warns about double negatives: "Double boolean
>>>> negation found". Linters in other languages have a similar warning. Other
>>>> languages have a built-in function (JavaScript has Boolean()) to convert to
>>>> boolean.
>>>> 4. The alternative to double-negative is verbose: "if expr, do: true,
>>>> else: false", or the less readable "expr && true || false"
>>>>
>>>> I would be happy to submit a PR to add Kernel.to_boolean/1.
>>>>
>>>> On Sunday, November 1, 2015 at 5:48:28 AM UTC-8 José Valim wrote:
>>>>
>>>>> Not necessarily , but the ones in Kernel are. :)
>>>>>
>>>>> --
>>>>>
>>>>>
>>>>> *José Valim*
>>>>> www.plataformatec.com.br
>>>>> Skype: jv.ptec
>>>>> Founder and Director of R&D
>>>>>
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>>>>
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