PHP Internals News: Episode 70: Explicit Octal Literal

PHP Internals News: Episode 70: Explicit Octal Literal



Thursday, November 12th 2020, 09:33 GMT


London, UK



In this episode of "PHP Internals News" I talk with
George Peter Banyard (Website, Twitter, GitHub, GitLab)
about an RFC that he has proposed to add an Explicit
Octal Literal to PHP.


The RSS feed for this podcast is
https://derickrethans.nl/feed-phpinternalsnews.xml, you
can download this episode's MP3 file, and it's available
on Spotify and iTunes. There is a dedicated website:
https://phpinternals.news


Transcript

Derick Rethans 0:15

Hi, I'm Derick, and this is PHP internals news, a
weekly podcast dedicated to demystifying the
development of the PHP language.
Derick Rethans 0:24

This is Episode 70. Today I'm talking with George
Peter Banyard, about a new RFC that he's just
proposed for PHP 8.1, which is titled explicit octal
literal. Hello George, would you please introduce
yourself?
George Peter Banyard 0:38

Hello Derick, I'm George Peter Banyard, I'm a student
at Imperial College London, and I contribute to PHP
in my free time.
Derick Rethans 0:46

Excellent, and the contribution that you're currently
have up is titled: explicit octal literal. What is
the problem that this is trying to solve?
George Peter Banyard 0:56

Currently in PHP, we have four types of integer
literals. So decimal numbers, hexadecimal, binary,
and octal. Decimal is just your normal decimal
numbers; hexadecimal starts with 0x, and then
hexadecimal characters so, null to nine and A to F,
and then binary starts with 0b, and then it's only
zeros and ones. However, octal notation is just a
decimal, something which looks like a decimal number,
which was a leading zero, which doesn't really look
that much different than a decimal number, but it
comes from the days from C and everything which just
uses like a zero as a prefix.
Derick Rethans 1:48

But I have seen is people using like array keys for
the, for the month names right and they use 01, 02,
03, you get 07, and 08 and 09, and then they look at
the arrays. They notice that they actually had the
zeroth element in there but no, but no eight or nine.
That's something that is that PHP no longer does I
believe. No, it's mostly that the parser doesn't pick
it up anymore. Instead of silently ignoring the
eight, it'll just give you an error. You've mentioned
that there's these four types of numbers with octal
being the one started with zero. But what's the
problem with is that a moment?
George Peter Banyard 2:31

Sometimes when you want to use, which looks like
decimal number. So, for example, you're trying to
order months, and use like the full two digits for
the month number, instead of just one, you use 01, as
an array key. When you get to array, it will parse
error because it can't pass 08 as an octal number,
which is very confusing, because it. Most people
don't deal with octal numbers that often, and you
would expect everything to be decimal. Because
numeric strings are always decimal, but not integers
literals. So, the proposal is to add an explicit
octal notation, which would be 0o. So python does
that, JavaScript has it, Rust also has it, to allow
like a by more explicit to say oh I'm dealing with an
octal number here. This is intended.
Derick Rethans 3:33

Beyond having the 0b for binary, and the 0x for
hexadecimal, the addition of 0o for octal is the plan
to add. And is that it?
George Peter Banyard 3:45

That's more or less the proposal. It's non-BC,
because the parser before would just parse or if you
had 0o, so there's no PC very possible numeric
strings are not affected because since PHP 7.0
hexadecimal strings are not handled anymore as
numeric strings. Numeric strings will always be
decimal integers, literals will have your four
different variants, and maybe a future proposal is to
deprecate the implicit octal notation to always make
a decimal, even if you have leading zeros.
Derick Rethans 4:21

At the moment, if I do as a string literal 014, and
do an echo that I get 12.
George Peter Banyard 4:27

Because then it's interpreted as an octal. The most
bizarre example is if you do var_dump string of 014
double equal to 014, you will get false, because one
is interpreted as well 14, like the numeric string is
interpreted as 14, whereas the octal number, which
says 014 as an integer literal is interpreted as an
octal number, which is 12, which is slightly
confusing for most people, because that also if you
because PHP, most, we all deal with like HTTP
requests, and I GET and POST a data, which everything
is in strings because it's a text protocol. And if
you get user output, which is like I don't know,
naught 14 and you're, are you intending to compare
munz numbers which are or. 01201, and then you get to
array, well then you just fail.
Derick Rethans 5:22

Of course, removing that support means a BC breaking
change, which phones happen until PHP nine, of
course, which might be a while away from now let's
say that.
George Peter Banyard 5:31

Probably five years, if we're going through the
timelines from PHP seven to PHP 8, but to be able to
deprecated and remove it. Well, you need to add
support for something else. So that's more the long
term plan.
Derick Rethans 5:46

And your proposal is basically to make it equivalent
to binary and hexadecimal numbers, so that it is less
confusing in general.
George Peter Banyard 5:55

Yes, that's why the RFC is very short.
Derick Rethans 5:58

What are octal numbers actually used for?
George Peter Banyard 6:02

The only practical use case that I've seen is for
Linux permissions, so chmod. Execute read and write,
are those who permissions which chmod will use an
octal number.
Derick Rethans 6:15

In a different order though but
George Peter Banyard 6:17

Yes, I don't know chmod though on top of my heart.
Derick Rethans 6:20

Is it only Linux permissions that you can think of?
Is there anything else? I can't either so I'm asking
you.
George Peter Banyard 6:25

No, I can't. That's why I find it very odd that like
the leading zero just makes it octal instead of
anything else. I mean it has precedence because many
other languages do that like C, Java, I don't know,
many any language I suppose was just picked it up
from. I think C. But when I looked into the history,
weirdly enough before C. They had a prefix for like
binary, octal, and dec, and hexadecimal. But then the
one for octal just got dropped, for some reason.
Derick Rethans 6:57

Maybe because the zero and the "o" next each other
look very the same. We've already touched on whether
there are BC breaks or not, BC standing for backwards
compatibility. And, there shouldn't be any because
it's something that a parser currently doesn't
understand. But do other build-in extensions need to
be modified for example?
George Peter Banyard 7:18

We have two extensions, which one which deals with
numbers, so which is GMP, which is arbitrary
precision arithmetic. And then there's the filter
extension to filter octal, which filters data and
tells you if it's valid or not and it gives you back
a, like a correct integer or something like that,
which is the filter extension, which has an octal
filter. Both of these extensions have been modified
to support like the prefix notation, and interpreted
as a valid octal number. And then we have like the
function which is oct2dec, which is basically octal
to decimal, which which weirdly enough already
supported like the octal prefix.
Derick Rethans 7:59

But that accepts strings, I suppose?
George Peter Banyard 8:01

Yes that that accepts strings.
Derick Rethans 8:04

And it already supported the 0o prefix?
George Peter Banyard 8:07

Yes, which is very on point for PHP I feel. Some
things are just supported randomly in one side but
not everywhere else.
Derick Rethans 8:15

It's a surprise for me that is what I can say. So,
yeah, you mentioned as a short RFC, you think there
will be any extensions to this in the future? You
already mentioned having it maybe deprecating the
current just zero prefix?
George Peter Banyard 8:31

So one other possible future scope is with the prefix
to reintroduce octal, binary, and hexadecimal
numbers. As with the prefixes as numeric strings. If
you type, 0xAABBCC in, and you have that as a string,
which could be useful if you get like colorus back
from, from a webform, that would be automatically
converted into an integer, or not automatically
converted if you do like if you compare it to
numbers, or if you cast it to an integer, because
currently if you get 0x, something and you cast it to
an integer, you will get zero. So that way you need
to use like a function like hex2dec, or oct2dec, or
bin2dec to convert from a string, or to another
string and then cast that. Or it may be cast directly
to an integer, I'm not exactly sure. But that's also
debatable if it's something we want to add.
Derick Rethans 9:37

Is it actually possible to do, for example with
hexadecimal numbers, do like if you have inside a
string. Can you do xAA, does that actually work?
George Peter Banyard 9:48

I didn't think so.
Derick Rethans 9:49

That actually works. You can do var_dump("x6A") and
it gives you the letter J.
George Peter Banyard 9:55

The more, you know.
Derick Rethans 9:56

But it doesn't work for binary, or octal. Only for
hexadecimal with x. So I guess that's something that
could be added to string interpolation at some point.
George Peter Banyard 10:07

PHP is so weird sometimes.
Derick Rethans 10:10

Yes, I mean PHP does things in its own way, however,
making this kind of small changes to it, just end up
improving the language step by step and that is of
course the way forward. Right.
George Peter Banyard 10:23

Yeah.
Derick Rethans 10:25

And I'm looking forward to more of these small
incremental changes in the future as well.
George Peter Banyard 10:30

Seems like a good plan.
Derick Rethans 10:32

Are you planning any more?
George Peter Banyard 10:34

Well, so I went through some of the old RFCs, most
notably the one about when the whole scalar type
thing was going on. We had like strict types and then
we had like the coercive types. One which was by
Dmitri, Zeev, pretty sure Stas, and um forgot,
forgetting somebody else. But some of them, some of
the ideas they had, which was making some of the type
juggling more strict, so float to integer
conversions. Currently, even if the floating number
has like decimal part, it will just truncate it to an
integer, and it won't emit any warning and it will
just like pass without any issue, I think that may be
is kind of unexpected. I made the other warning to
that to possibly make it a type error in the future.
Derick Rethans 11:24

You mean upon a cast?
George Peter Banyard 11:26

If you've type hint function as accepting only
integers, so if you say foo(int $bar), and you pass
it the float. And you would like in normal mode, it
will truncate, and it will just pass an integer.
Derick Rethans 11:40

Because it's just typed.
George Peter Banyard 11:42

Yes, and we've had multiple reports of people being
very confused about why it's just truncating the
numbers, because it's not even rounding up. If you
had like if you have like 0.9 it won't round up to
one it will just truncate to zero, which a lot of
people are confused by.
Derick Rethans 11:58

In strict mode doesn't do that?
George Peter Banyard 11:59

Yeah, because strict mode is very strict and will
only allow you to pass explicitly what's been what
you've requested, with the exception of the normal
integer to float conversion which is lossless.
Derick Rethans 12:12

That's lossless up to a certain point yes.
George Peter Banyard 12:14

To a certain point like your integer doesn't fit,
then it goes overflow to a float.
Derick Rethans 12:19

All right. George thank you very much for taking your
time this afternoon to talk to me.
George Peter Banyard 12:23

Thank you for having me.
Derick Rethans 12:26

Thanks for listening to this installment of PHP
internals news, the weekly podcast dedicated to
demystifying the development of the PHP language. I
maintain a Patreon account for supporters of this
podcast, as well as the Xdebug debugging tool. You
can sign up for Patreon at https://drck.me/patreon.
If you have comments or suggestions, feel free to
email them to derick@phpinternals.news. Thank you for
listening, and I'll see you next week.




Show Notes




RFC: Explicit octal integer literal notation






Credits



Music: Chipper Doodle v2 — Kevin MacLeod
(incompetech.com) — Creative Commons: By
Attribution 3.0