Thank you for the examples.
However, I believe those examples are not really checking for a boolean,
but rather for nil. If you don't want to use is_nil, you can always compare
with nil, which is also pipeable:
def has_access? do
at_least_logged_in? and get_csrf_cookie(session) != nil
end
%{event_form | submitted: event_form.submitted_at != nil}
case membership_ends_on || trial_ends_on || dues_exempt do
nil -> add_error(changeset, :membership_ends_on, "is required")
_ -> changeset
end
On Wed, Dec 23, 2020 at 7:04 PM Bruce Tate <br...@grox.io> wrote:
> 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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>>>
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>>
>
>
> --
>
> Regards,
> Bruce Tate
> CEO
>
>
> <https://bowtie.mailbutler.io/tracking/hit/f8218219-d2a8-4de4-9fef-1cdde6e723f6/c7c97460-016e-45fb-a4ab-0a70318c7b97>
>
> Groxio, LLC.
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> grox.io
>
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