> On 21 Oct 2014, at 00:27, Lars Strojny <l...@strojny.net> wrote:
>
> I like the proposal except for one thing: the functions returning false in
> case of an error. As the next logical function would be "to_bool()", I
> foresee a lot of trouble with regards to API design as returning false there
> either means successful cast to false or an error while casting. What about
> changing the functions to take an $isError variable as a second argument?
>
> $value = to_string(1.2, $isError);
> if ($isError) {
> ...
> }
>
> Alternatively one could do the same thing with an $isSuccess variable:
>
> $value = to_string(1.2, $isSuccess);
> if (!$isSuccess) {
> ...
> }
>
> Thoughts?
This is an interesting question. It’s actually one I’d considered myself, I
think I briefly mention it in the RFC. However, I don’t expect it to be a
problem, and the reason is really quite simple: There’s no clear-cut
one-size-fits all boolean casting function you could make, and booleans are
trivial to validate yourself.
Adding something like is_bool() would be possible, the problem is what
behaviour it would have, and there are too many possibilities. Do you accept 1
and 0? If so, do you accept all non-zero values, or not? Is “true” TRUE or is
it FALSE? Is “yes” TRUE or is it FALSE? Do “true” and “yes” validate? Do they
not? Does the empty string validate? Does it not? Bear in mind that boolean
casting was one of the most problematic areas of the abandoned Scalar Type
Hinting RFC: there’s no clear set of definitely boolean values, nor a clear
idea of which mean which boolean value. Basically, I don’t think we’d ever be
able to draw the line.
The other thing is, well, there’s not really a need. You can quite simply do
something like this: if ($value !== “true” && $value === “false”) { /* error!
*/ } - and while this is less convenient than is_bool, as I mentioned before,
there’s no real agreement on what is_bool should do so you’d have to do this
anyway. A thought: A weird, but workable solution for one particular style is
[“true” => TRUE, “false” => FALSE][$value] ?? NULL - whether that’s a wonderful
or horrible use of PHP is up to you. ;)
So I don’t think using FALSE here is a problem, since I doubt is_bool would
ever be added.
Regarding using a reference variable for the output, I don’t like that idea
much. It doesn’t chain very well… and would it fail a strict type hint, if we
added that? Even if it somehow did, I don’t think it is a good idea. Since I
don’t think is_bool will happen, there’s also no real need, either.
--
Andrea Faulds
http://ajf.me/
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