New method on java.util.function.Function -- ternary method

[David Alayachew]

It has been a month since I sent this proposal. Since no one has told me
that this is a terrible idea, I will submit this as an enhancement to JBS,
and once the ticket is made, start work on creating a pull request.

On Tue, Oct 3, 2023 at 3:13 AM David Alayachew <davidalayachew at gmail.com>
wrote:

> Whoops, bad import.
>
> Please replace the following line with the one after it.
>
> > import java.util.function.Function;
>
> > import java.util.function.*;
>
> On Tue, Oct 3, 2023 at 3:09 AM David Alayachew <davidalayachew at gmail.com>
> wrote:
>
>> Hello all,
>>
>> I have an idea that I want to run by you all -- a new method on
>> java.util.function.Function to capture ternary operations.
>>
>> Here is a mockup of what I wanted to do.
>>
>> >
>> > import java.util.function.Function;
>> >
>> > @FunctionalInterface
>> > public interface Function2<I, O> extends Function<I, O>
>> > {
>> >
>> >    public static <I, O> Function<I, O> ternary
>> >    (
>> >        Predicate<I> test,
>> >        Function<I, O> trueOutput,
>> >        Function<I, O> falseOutput
>> >    )
>> >    {
>> >
>> >       return
>> >           (I input) ->
>> >               test.test(input)
>> >               ? trueOutput.apply(input)
>> >               : falseOutput.apply(input)
>> >               ;
>> >
>> >    }
>> >
>> > }
>> >
>>
>> I think this is useful for a few reasons.
>>
>>  * This composes, just like the ternary operator itself.
>>
>>  * It pairs well with Function.identity() and method references to
>> clearly (but concisely) communicate intent.
>>
>>  * Ternary operations are common, so this will find great use by
>> developers of all sorts.
>>
>> There is at least one part I don't quite like about this design - what if
>> one (or both!) of your outputs is not a functional transformation of the
>> input?
>>
>> For example, String username = id.isBlank() ? "UNKNOWN" : lookup(id);
>>
>> Obviously, this is easy to work around - simply ignore the input of the
>> function. But you lose clarity and simplicity that way. I would put a note
>> in the javadoc that says that this method should only be used in instances
>> where both outputs are a functional transformation of the input. That way,
>> intent is clarified. But if we go that route, maybe this function should
>> get a better name to capture that? testThenApply? ternaryTransform?
>> ternaryApply?
>>
>> Thank you for your time and help!
>> David Alayachew
>>
>
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