Re: $value but lexically ...
[EMAIL PROTECTED] wrote:
Would this work too?
0 but role {}
Most certainly, but you would have no way to refer to that role later,
so it is questionable how useful that construct is. No, it's not
questionable. That is a useless construct.
Luke
Can an inline role be named?
0 but role is_default {}
Miro
Re: $value but lexically ...
Miroslav Silovic skribis 2005-10-07 13:07 (+0200):
Can an inline role be named?
0 but role is_default {}
This is a nice idea. It would require named roles (and to really be
succesful, also classes, subs, methods, ...) declarations to be
expressions, but I see no downside to that.
Juerd
--
http://convolution.nl/maak_juerd_blij.html
http://convolution.nl/make_juerd_happy.html
http://convolution.nl/gajigu_juerd_n.html
Re: $value but lexically ...
On 10/7/05, Juerd [EMAIL PROTECTED] wrote:
Miroslav Silovic skribis 2005-10-07 13:07 (+0200):
Can an inline role be named?
0 but role is_default {}
This is a nice idea. It would require named roles (and to really be
succesful, also classes, subs, methods, ...) declarations to be
expressions, but I see no downside to that.
Well, I see a cognitive downside. That is, package declarations (the
default) don't create closures. It's like this:
sub foo($x) {
sub bar() {
return $x;
}
return bar;
}
foo(42).(); #
Restricting expressions to anonymous subs forces you to say what you
mean. Because sometimes when you say:
0 but role is_default { }
You're going to mean package role, and some of the time you're going
to mean lexical. I'd be more in favor of:
0 but my role is_default { }
In fact, it may be the case that that's already valid.
Luke
Re: $value but lexically ...
Luke Palmer skribis 2005-10-07 15:31 (-0600):
Well, I see a cognitive downside. That is, package declarations (the
default) don't create closures. It's like this:
sub foo($x) {
sub bar() {
return $x;
}
return bar;
}
foo(42).(); #
Does this mean that this Perl 5 snippet no longer does the same in Perl 6?
{
my $foo = 5;
sub bar {
return $foo;
}
}
Juerd
--
http://convolution.nl/maak_juerd_blij.html
http://convolution.nl/make_juerd_happy.html
http://convolution.nl/gajigu_juerd_n.html
Re: $value but lexically ...
On 10/7/05, Juerd [EMAIL PROTECTED] wrote:
Luke Palmer skribis 2005-10-07 15:31 (-0600):
sub foo($x) {
sub bar() {
return $x;
}
return bar;
}
foo(42).(); #
Does this mean that this Perl 5 snippet no longer does the same in Perl 6?
{
my $foo = 5;
sub bar {
return $foo;
}
}
Uh no. Okay, when I said that they don't close, I guess I meant
they don't close like anonymous routines do. It works precisely like
Perl 5's:
sub foo {
my $foo = 5;
sub bar {
return $foo;
}
return \bar;
}
I don't think I've ever seen that used in Perl 5. Closing over that
$foo doesn't mean anything. That's why we're allowing my before
such declarations now, so that they can close over something useful.
Luke
Re: $value but lexically ...
On Fri, Oct 07, 2005 at 03:46:02PM -0600, Luke Palmer wrote:
Uh no. Okay, when I said that they don't close, I guess I meant
they don't close like anonymous routines do. It works precisely like
Perl 5's:
sub foo {
my $foo = 5;
sub bar {
return $foo;
}
return \bar;
}
I don't think I've ever seen that used in Perl 5. Closing over that
$foo doesn't mean anything.
Well strictly speaking it means that bar() captures the first instance of
foo()'s $foo, which isn't often very useful.
--
The Enterprise successfully ferries an alien VIP from one place to another
without serious incident.
-- Things That Never Happen in Star Trek #7
$value but lexically ...
Cbut properties get attached to a value, and are available when the
value is passed to other functions/ etc. I would like to be able to
define a property of a value that is trapped in the lexical scope where
it is defined. The example that set me thinking down this path is
sub foo( $a, ?$b = rand but :is_default )
{
...
bar($a,$b);
}
sub bar( $a, ?$b = rand but :is_default )
{
warn defaulting \$b = $b if $b.is_default;
...
}
It would be unfortunate if the is_default property attached in foo
triggers the warning in bar. So I'd like to say somthing like
sub foo( $a, ?$b = 0 but lexically :is_default ) {...}
or
sub foo( $a, ?$b = 0 but locally :is_default ) {...}
to specify that I don't want the property to the propagated.
Re: $value but lexically ...
On 10/6/05, Dave Whipp [EMAIL PROTECTED] wrote:
sub foo( $a, ?$b = rand but :is_default )
{
...
bar($a,$b);
}
sub bar( $a, ?$b = rand but :is_default )
{
warn defaulting \$b = $b if $b.is_default;
...
}
It would be unfortunate if the is_default property attached in foo
triggers the warning in bar. So I'd like to say somthing like
sub foo( $a, ?$b = 0 but lexically :is_default ) {...}
or
sub foo( $a, ?$b = 0 but locally :is_default ) {...}
to specify that I don't want the property to the propagated.
This came up before when I proposed lexical properties. That was
before we knew that a property was just a role. So you can do a
lexical property like so:
{
my role is_default {} # empty
sub foo($a, ?$b = 0 but is_default) {...}
}
{
my role is_default {}
sub bar($a, ?$b = rand but is_default) {...}
}
If this turns out to be a common want, I can see:
sub bar($a, ?$b = rand but my $is_default) {
warn Defaulted to $b if $b.does($is_default);
}
But I don't think it will be, and the empty role is easy enough.
Luke
Re: $value but lexically ...
Luke Palmer skribis 2005-10-06 14:23 (-0600):
my role is_default {} # empty
sub foo($a, ?$b = 0 but is_default) {...}
Would this work too?
0 but role {}
Juerd
--
http://convolution.nl/maak_juerd_blij.html
http://convolution.nl/make_juerd_happy.html
http://convolution.nl/gajigu_juerd_n.html
Re: $value but lexically ...
On 10/6/05, Juerd [EMAIL PROTECTED] wrote:
Luke Palmer skribis 2005-10-06 14:23 (-0600):
my role is_default {} # empty
sub foo($a, ?$b = 0 but is_default) {...}
Would this work too?
0 but role {}
Most certainly, but you would have no way to refer to that role later,
so it is questionable how useful that construct is. No, it's not
questionable. That is a useless construct.
Luke
