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Date: Fri, 13 Mar 2015 22:32:34 -0600
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To: Rasmus Lerdorf <rasmus@lerdorf.com>
Cc: Zeev Suraski <zeev@zend.com>, Dmitry Stogov <dmitry@zend.com>, 
	"francois@php.net" <francois@php.net>, PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [VOTE][RFC] Coercive Scalar Type Hints
From: levim@php.net (Levi Morrison)

On Fri, Mar 13, 2015 at 10:31 PM, Levi Morrison <levim@php.net> wrote:
> On Fri, Mar 13, 2015 at 8:50 PM, Rasmus Lerdorf <rasmus@lerdorf.com> wrote:
>> On Mar 14, 2015, at 13:37, Levi Morrison <levim@php.net> wrote:
>>> It seems that `float -> bool` is always disallowed. If I am correct
>>> `int -> bool` is permitted for all values (not just 0 and 1), which
>>> means that floats which can be converted to integers without dataloss
>>> should also be permitted to be booleans. If a specific float can be
>>> converted to an int, and all ints can be converted to booleans, then
>>> the transitive property should hold for that float to a bool.
>>
>> The problem there is what does "without dataloss" mean? At which precision do you consider there to be no dataloss?
>
> Ah, I reread part of the RFC. It appears `float -> int` is unchanged
> from current. This only confuses me more, though. If int -> float is
> permitted, and float -> int is permitted, I do not understand why
> float -> bool is not permitted.
>
> Can someone clarify this?

I apologize; my hands didn't keep up with my brain. I meant that if
`int -> bool` is permitted, and `float -> int` is permitted, then by
transitive property I would expect `float -> bool` to be permitted.
Can someone clarify why this is not the case? The RFC does not appear
to justify this behavior (that I can find, anyway).