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Date: Tue, 28 Mar 2023 18:03:46 +0200
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To: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [RFC] Define proper semantics for range() function
From: cschneid@cschneid.com (Christian Schneider)

Am 28.03.2023 um 14:42 schrieb G. P. B. <george.banyard@gmail.com>:
> On Tue, 28 Mar 2023 at 08:19, Christian Schneider =
<cschneid@cschneid.com> wrote:
>> There are two cases I would handle differently:
>> - I'm not sure why a negative step for $start > $end is considered =
wrong, I consider range(10, 0, -2) at least as logical/readable as using =
a positive decrement of 2. Not requiring a sign for steps seems weirder =
to me but that's something we cannot change. *BUT* if it is the result =
of a calculation it seems wrong to require an abs() around it. I do see =
the reason for a warning/error when $start < $end and $step < 0.
>>=20
> Considering the only other programming language that I know of that =
has a range() function that accepts a step argument is Python, and its =
behaviour is IMHO worse.
> For increasing ranges it requires a positive step, and if not just =
generates an empty range. For decreasing ranges it requires a negative =
step, and if not just generates an empty range (this applies even if =
using the default step value of 1 which is bonkers).
>=20
> Making it a requirement to pass a negative step is definitely out of =
the question.
> Making it okay to use negative steps *only* for decreasing ranges =
could be sensible, but we check for the step parameter way before we =
look into the boundary values because those are different for int, float =
and string boundaries.
> Moreover, I personally find it weirder to require a sign for negative =
steps as for me a step is something that *must* be positive

I quickly checked our own codebase and there is indeed one instance of
	range($last, 0, -1)
which was not written by me so there is at least one more person who =
found this logical ;-)

>>  - Values of '' or null in integer context (e.g. range(null, 10, 2)) =
should IMHO emit a warning first, not directly be changed to a =
TypeError. The usual BC / migration concern :-)
>=20
> Trying to figure out if an empty string was used with another string =
boundary is tedious, as this information needs to somehow get carried =
around.
> A previous iteration of the PR used to convert empty strings to 0 with =
a warning, but considering the analysis I decide to just make this a =
ValueError as it doesn't seem that empty strings are actually used in =
practice.
> But this is an easy revert, and I'm not really bound to this decision.

Even though this might be a bit cumbersome at the moment I think this =
would be an important transition step as currently
	range('', 10, 2);
returns the (somewhat) expected result of 0, 2, 4, 6, 8, 10 so I'd be in =
favor of first giving a warning and then changing it to a ValueError.

- Chris