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Date: Tue, 04 Feb 2025 23:30:44 +0100
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Subject: Re: [PHP-DEV] Pattern matching details questions
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From: rob@bottled.codes ("Rob Landers")

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On Tue, Feb 4, 2025, at 22:16, Larry Garfield wrote:
> On Tue, Feb 4, 2025, at 1:14 PM, Marc Bennewitz wrote:
> > On 04.02.25 08:51, Rob Landers wrote:
> >>=20
> >>=20
> >> On Tue, Feb 4, 2025, at 05:31, Larry Garfield wrote:
> >>> Hi folks.  Ilija is still working on the implementation for the pa=
ttern matching RFC, which we want to complete before proposing it offici=
ally in case we run into implementation challenges.
> >>>=20
> >>> Such as these, on which we'd like feedback on how to proceed.
>=20
>=20
> >>> [1] https://github.com/Crell/php-rfcs/blob/master/pattern-matching=
/research.md
> >>>=20
> >>> --=20
> >>>   Larry Garfield
> >>>   larry@garfieldtech.com
> >>>=20
> >>=20
> >> Hey Larry,
> >>=20
> >> Instead of symbols, why not use words?
> >>=20
> >> We already have &&, but it looks like this uses & instead, which is=
 a bitwise-and. But the language does have =E2=80=9Cand=E2=80=9D as a ke=
yword. So instead of:
> >>=20
> >> $value is int & &$x
> >>=20
> >> It would be:
> >>=20
> >> $value is int and &$x
> >>=20
> >> Which removes the confusion you mentioned before (also for someone =
like me who uses bitwise-and quite a bit).
> >>=20
> >> =E2=80=94 Rob
>=20
> Patterns are deliberately designed as a superset of existing DNF types=
.  You can already have a type of Foo&Bar, so we want the pattern for "i=
nstanceof Foo || instanceof Bar" to be the same.  That means & and | for=
 conjunctions is necessary.  Also supporting "and" and "or" would techni=
cally be possible, but wouldn't resolve the issue (since & would still b=
e needed either way) and would just add more complication, confusion, an=
d inconsistency.  I don't think that's viable.

Interesting way of looking at it, not wrong either. I guess I'm not used=
 to this syntax that much. It's like reading the following statement and=
 working out what the value is without running it:

add($a =3D add($a =3D 2, $a), $a =3D add($a, $a)) + $a;

To me, mixing up both setting and using values in the same statement rea=
ds like above. Once you work out how it works, it makes sense that the f=
irst parameter is 4 and the second is 8, with $a =3D=3D 8 and the result=
 being 20 (https://3v4l.org/MPb5P). It takes some getting used to, thoug=
h, and only works because we intrinsically understand the parser to AST =
to opcodes -- even if we don't know the details.

Personally, it might be worth adding binding/setting values until a late=
r RFC just to reduce the complexity until people get used to it. Right n=
ow, you (and maybe a couple of others) are probably the only people on e=
arth who can truly understand how the syntax actually works; the rest of=
 us may not _yet_ be equipped to give useful feedback.

It won't stop me from trying to help, but I also don't want to waste you=
r time by saying incredibly incorrect statements like using "and" instea=
d of "&" to denote a type. :)

=E2=80=94 Rob
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<!DOCTYPE html><html><head><title></title><style type=3D"text/css">p.Mso=
Normal,p.MsoNoSpacing{margin:0}=0Ap.MsoNormal,p.MsoNoSpacing{margin:0}</=
style></head><body><div><br></div><div><br></div><div>On Tue, Feb 4, 202=
5, at 22:16, Larry Garfield wrote:<br></div><blockquote type=3D"cite" id=
=3D"qt" style=3D""><div>On Tue, Feb 4, 2025, at 1:14 PM, Marc Bennewitz =
wrote:<br></div><div>&gt; On 04.02.25 08:51, Rob Landers wrote:<br></div=
><div>&gt;&gt;&nbsp;<br></div><div>&gt;&gt;&nbsp;<br></div><div>&gt;&gt;=
 On Tue, Feb 4, 2025, at 05:31, Larry Garfield wrote:<br></div><div>&gt;=
&gt;&gt; Hi folks.&nbsp; Ilija is still working on the implementation fo=
r the pattern matching RFC, which we want to complete before proposing i=
t officially in case we run into implementation challenges.<br></div><di=
v>&gt;&gt;&gt;&nbsp;<br></div><div>&gt;&gt;&gt; Such as these, on which =
we'd like feedback on how to proceed.<br></div><div><br></div><div><br><=
/div><div>&gt;&gt;&gt; [1]&nbsp;<a href=3D"https://github.com/Crell/php-=
rfcs/blob/master/pattern-matching/research.md">https://github.com/Crell/=
php-rfcs/blob/master/pattern-matching/research.md</a><br></div><div>&gt;=
&gt;&gt;&nbsp;<br></div><div>&gt;&gt;&gt; --&nbsp;<br></div><div>&gt;&gt=
;&gt;&nbsp;&nbsp; Larry Garfield<br></div><div>&gt;&gt;&gt;&nbsp;&nbsp;&=
nbsp;<a href=3D"mailto:larry@garfieldtech.com">larry@garfieldtech.com</a=
><br></div><div>&gt;&gt;&gt;&nbsp;<br></div><div>&gt;&gt;&nbsp;<br></div=
><div>&gt;&gt; Hey Larry,<br></div><div>&gt;&gt;&nbsp;<br></div><div>&gt=
;&gt; Instead of symbols, why not use words?<br></div><div>&gt;&gt;&nbsp=
;<br></div><div>&gt;&gt; We already have &amp;&amp;, but it looks like t=
his uses &amp; instead, which is a bitwise-and. But the language does ha=
ve =E2=80=9Cand=E2=80=9D as a keyword. So instead of:<br></div><div>&gt;=
&gt;&nbsp;<br></div><div>&gt;&gt; $value is int &amp; &amp;$x<br></div><=
div>&gt;&gt;&nbsp;<br></div><div>&gt;&gt; It would be:<br></div><div>&gt=
;&gt;&nbsp;<br></div><div>&gt;&gt; $value is int and &amp;$x<br></div><d=
iv>&gt;&gt;&nbsp;<br></div><div>&gt;&gt; Which removes the confusion you=
 mentioned before (also for someone like me who uses bitwise-and quite a=
 bit).<br></div><div>&gt;&gt;&nbsp;<br></div><div>&gt;&gt; =E2=80=94 Rob=
<br></div><div><br></div><div>Patterns are deliberately designed as a su=
perset of existing DNF types.&nbsp; You can already have a type of Foo&a=
mp;Bar, so we want the pattern for "instanceof Foo || instanceof Bar" to=
 be the same.&nbsp; That means &amp; and | for conjunctions is necessary=
.&nbsp; Also supporting "and" and "or" would technically be possible, bu=
t wouldn't resolve the issue (since &amp; would still be needed either w=
ay) and would just add more complication, confusion, and inconsistency.&=
nbsp; I don't think that's viable.<br></div></blockquote><div><br></div>=
<div>Interesting way of looking at it, not wrong either. I guess I'm not=
 used to this syntax that much. It's like reading the following statemen=
t and working out what the value is without running it:</div><div><br></=
div><div>add($a =3D add($a =3D 2, $a), $a =3D add($a, $a)) + $a;<br></di=
v><div><br></div><div>To me, mixing up both setting and using values in =
the same statement reads like above. Once you work out how it works, it =
makes sense that the first parameter is 4 and the second is 8, with $a =3D=
=3D 8 and the result being 20 (<a href=3D"https://3v4l.org/MPb5P">https:=
//3v4l.org/MPb5P</a>). It takes some getting used to, though, and only w=
orks because we intrinsically understand the parser to AST to opcodes --=
 even if we don't know the details.<br></div><div><br></div><div>Persona=
lly, it might be worth adding binding/setting values until a later RFC j=
ust to reduce the complexity until people get used to it. Right now, you=
 (and maybe a couple of others) are probably the only people on earth wh=
o can truly understand how the syntax actually works; the rest of us may=
 not _yet_ be equipped to give useful feedback.<br></div><div><br></div>=
<div>It won't stop me from trying to help, but I also don't want to wast=
e your time by saying incredibly incorrect statements like using "and" i=
nstead of "&amp;" to denote a type. :)<br></div><div><br></div><div id=3D=
"sig121229152">=E2=80=94 Rob<br></div></body></html>
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