I think there's a stronger argument to be made for literal true / false,
not just truthy / falsy in Elixir than Ruby.
In Ruby, the return value might be used in an if-condition. Semantically,
it shouldn't matter if the value is literal true or simply truthy.
Something like `if method? == true` would be considered bad code.
In Elixir, you might also use the value in pattern matching. Matching on
literal `true` would be considered completely reasonable. Example:
def entrypoint(data), do: handle(data, valid?(data))
def handle(data, true), do: something(data)
def handle(data, false), do: something_else(data)
Returning truthy / falsy values would hobble this sort of pattern matching.
It would be even worse if I only did a literal match on false, and ignored
the in the true case, which would then be run for the falsy value nil.
Another consideration is that a truthy value could potentially be large,
and could then be sent off in a message to another process in the
expectation that it's small.
So please, return literal true / false from your predicate functions.
- Martin
ons 24 aug. 2016 kl 15:28 skrev Michał Muskała <mic...@muskala.eu>:
>
> > On 24 Aug 2016, at 15:24, Elliot Crosby-McCullough <elliot...@gmail.com>
> wrote:
> >
> > Follow-up question; there's debate in Ruby as to whether methods ending
> in `?` are supposed to return actual booleans or just "truthy" and "falsy"
> values.
> >
> > Is there a similar debate in Elixir or has it been more strictly defined?
>
> I've heard José state, that if it were possible, it would be an error for
> a ? function to return a non-boolean. I am equally of conviction that only
> strictly boolean values make sense in this context.
>
> Michał.
>
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