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Date: Thu, 17 Jun 2021 16:45:39 +0200
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Subject: Re: [PHP-DEV] [Vote] Partial Function Application
From: come.chilliet@fusiondirectory.org (=?UTF-8?B?Q8O0bWU=?= Chilliet)

Le Thu, 17 Jun 2021 08:37:23 -0500,
"Larry Garfield" <larry@garfieldtech.com> a =C3=A9crit :

> On Thu, Jun 17, 2021, at 2:54 AM, C=C3=B4me Chilliet wrote:
> > > $c =3D stuff(...);
> > > $c =3D fn(int $i, string $s, float $f, Point $p, int $m =3D 0) =20
> > >   =3D> stuff($i, $s, $f, $p, $m); =20
> >  =20
> > > $c =3D stuff(1, 'hi', 3.4, $point, 5, ...);
> > > $c =3D fn(...$args) =3D> stuff(1, 'hi', 3.4, $point, 5, ...$args); =20
> >=20
> > Why is there an additional variadic parameter in this one? =20
>=20
> ... means "zero or more".  In this case, it means zero, that is, it creat=
es a
> closure that requires no arguments and will call the original function wi=
th
> all of the provided values later.  This is the "deferred function" use ca=
se
> mentioned further down.

I still do not understand why there is an added variadic parameter when
 using ... in stuff(1, 'hi', 3.4, $point, 5, ...); but not when using it in
 stuff(...);
What happens when we use stuff(1, 'hi', 3.4, $point, ...); ?

> > Also, in the second set of examples: =20
> > > function things(int $i, float $f, Point ...$points) { ... } =20
> >   =20
> > > // Ex 13
> > > $c =3D things(...);
> > > $c =3D fn(int $i, float $f, ...$args) =3D> things(...[$i, $f, ...$arg=
s]); =20
> >   =20
> > > // Ex 14
> > > $c =3D things(1, 3.14, ...);
> > > $c =3D fn(...$args) =3D> things(...[1, 3.14, ...$args]); =20
> >=20
> > What happens to the typing of the variadic parameter here? Why is it
> > removed?
> >=20
> > It would feel natural that the ... means "copy the rest of the paramete=
rs
> > from signature". Here it seems it sometimes mean that, and sometimes me=
an
> > "accept an additional variadic parameter and pass it along". =20
>=20
> Internally placeholders do mean the former.  A trailing variadic, though,=
 can
> accept extra arguments of potentially not pre-defined types, so it sort of
> straddles the line.  Variadics make things weird. :-)  (Dating from PHP
> 5.6.)  In the majority case, though, thinking of them as "copy the rest of
> the arguments" is accurate.

I do not understand why Points ...$points becomes untyped ...$args when usi=
ng
 things(...), while when using stuff(...) earlier no typing was lost.

C=C3=B4me