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

[David Alayachew]

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
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mail.openjdk.org/pipermail/core-libs-dev/attachments/20231003/ade335bb/attachment.htm>