Extra . needed
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I was playing with classes and adding a closure to an attribute.
I discovered that to call a closure on object I need `.()` rather than
just `()`. See REPL below.
raku
Welcome to 𝐑𝐚𝐤𝐮𝐝𝐨™ v2020.12.
Implementing the 𝐑𝐚𝐤𝐮™ programming language v6.d.
Built on MoarVM version 2020.12.
To exit type 'exit' or '^D'
> class A { has &.f = -> { 'xyz' }}
(A)
> my A $a .=new
A.new(f => -> { #`(Block|94272504746848) ... })
> say $a.f()
-> { #`(Block|94272504749656) ... }
> say $a.f.()
xyz
>
I was wondering whether it was intended for `()` to return something
other than `.()`?
My first thought would be that `.()` would have the same syntactic sugar
as `.[]` on an Array object.
I looked in the Documentation and in Classes found
&!callback();
inside class Task.
So I think there may be something a bit wrong. Or is this an artifact of
REPL?
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<p>I was playing with classes and adding a closure to an attribute.</p>
<p>I discovered that to call a closure on object I need `.()` rather
than just `()`. See REPL below.</p>
<p>raku<br>
Welcome to 𝐑𝐚𝐤𝐮𝐝𝐨™ v2020.12.<br>
Implementing the 𝐑𝐚𝐤𝐮™ programming language v6.d.<br>
Built on MoarVM version 2020.12.<br>
<br>
To exit type 'exit' or '^D'<br>
> class A { has &.f = -> { 'xyz' }}<br>
(A)<br>
> my A $a .=new<br>
A.new(f => -> { #`(Block|94272504746848) ... })<br>
> say $a.f()<br>
-> { #`(Block|94272504749656) ... }<br>
> say $a.f.()<br>
xyz<br>
> <br>
</p>
<p><br>
</p>
<p>I was wondering whether it was intended for `()` to return
something other than `.()`?</p>
<p>My first thought would be that `.()` would have the same
syntactic sugar as `.[]` on an Array object.</p>
<p>I looked in the Documentation and in Classes found <br>
</p>
<div class="line"><span class="source raku"><span class="meta block
raku"><span class="meta block raku"><span class="meta block
raku"><span></span></span></span></span></span></div>
<div class="line"><span class="source raku"><span class="meta block
raku"><span class="meta block raku"><span class="meta block
raku"><span> </span><span class="meta variable
container raku"><span class="variable other identifier
sigil raku"><span>&</span></span><span
class="support class twigil raku"><span>!</span></span><span
class="variable other identifier raku"><span>callback</span></span></span><span>();</span></span></span></span></span></div>
<div class="line"><span class="source raku"><span class="meta block
raku"><span class="meta block raku"><span class="meta block
raku"><span>inside class Task.</span></span></span></span></span></div>
<div class="line"><span class="source raku"><span class="meta block
raku"><span class="meta block raku"><span class="meta block
raku"><span><br>
</span></span></span></span></span></div>
<div class="line"><span class="source raku"><span class="meta block
raku"><span class="meta block raku"><span class="meta block
raku"><span>So I think there may be something a bit wrong.
Or is this an artifact of REPL?<br>
</span></span></span></span></span></div>
</body>
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rnhainsworth
1/3/2021 6:30:00 PM
perl.perl6.users
1547 articles. 
0 followers.
3 Replies
17 Views
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You've already asked a similar question.
https://stackoverflow.com/questions/54033524/perl6-correctly-passing-a-rout=
ine-into-an-object-variable
When you call $a.f() you are getting the value in &!f which is a function.
When you call $a.f().() you are getting the value in &!f, and then also
calling that function.
You don't need the parens on a method call if they are empty.
So $a.f() is the same as $a.f
and $a.f().() is the same as $a.f.()
On Sun, Jan 3, 2021 at 12:30 PM Richard Hainsworth <rnhainsworth@gmail.com>
wrote:
> I was playing with classes and adding a closure to an attribute.
>
> I discovered that to call a closure on object I need `.()` rather than
> just `()`. See REPL below.
>
> raku
> Welcome to =F0=9D=90=91=F0=9D=90=9A=F0=9D=90=A4=F0=9D=90=AE=F0=9D=90=9D=
=F0=9D=90=A8=E2=84=A2 v2020.12.
> Implementing the =F0=9D=90=91=F0=9D=90=9A=F0=9D=90=A4=F0=9D=90=AE=E2=84=
=A2 programming language v6.d.
> Built on MoarVM version 2020.12.
>
> To exit type 'exit' or '^D'
> > class A { has &.f =3D -> { 'xyz' }}
> (A)
> > my A $a .=3Dnew
> A.new(f =3D> -> { #`(Block|94272504746848) ... })
> > say $a.f()
> -> { #`(Block|94272504749656) ... }
> > say $a.f.()
> xyz
> >
>
>
> I was wondering whether it was intended for `()` to return something othe=
r
> than `.()`?
>
> My first thought would be that `.()` would have the same syntactic sugar
> as `.[]` on an Array object.
>
> I looked in the Documentation and in Classes found
> &!callback();
> inside class Task.
>
> So I think there may be something a bit wrong. Or is this an artifact of
> REPL?
>
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<div dir=3D"ltr">You've already asked a similar question.<div><br></div=
><div><a href=3D"https://stackoverflow.com/questions/54033524/perl6-correct=
ly-passing-a-routine-into-an-object-variable">https://stackoverflow.com/que=
stions/54033524/perl6-correctly-passing-a-routine-into-an-object-variable</=
a><br></div><div><br></div><div>When you call $a.f() you are getting the va=
lue in &!f which is a function.</div><div><br></div><div>When you call =
$a.f().() you are getting the value in &!f, and then also calling that =
function.</div><div><br></div><div>You don't need the parens on a metho=
d call if they are empty.</div><div><br></div><div>So $a.f() is the same as=
$a.f</div><div>and $a.f().() is the same as $a.f.()</div></div><br><div cl=
ass=3D"gmail_quote"><div dir=3D"ltr" class=3D"gmail_attr">On Sun, Jan 3, 20=
21 at 12:30 PM Richard Hainsworth <<a href=3D"mailto:rnhainsworth@gmail.=
com">rnhainsworth@gmail.com</a>> wrote:<br></div><blockquote class=3D"gm=
ail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,=
204,204);padding-left:1ex">
=20
=20
=20
<div>
<p>I was playing with classes and adding a closure to an attribute.</p>
<p>I discovered that to call a closure on object I need `.()` rather
than just `()`. See REPL below.</p>
<p>raku<br>
Welcome to =F0=9D=90=91=F0=9D=90=9A=F0=9D=90=A4=F0=9D=90=AE=F0=9D=90=
=9D=F0=9D=90=A8=E2=84=A2 v2020.12.<br>
Implementing the =F0=9D=90=91=F0=9D=90=9A=F0=9D=90=A4=F0=9D=90=AE=E2=
=84=A2 programming language v6.d.<br>
Built on MoarVM version 2020.12.<br>
<br>
To exit type 'exit' or '^D'<br>
> class A { has &.f =3D -> { 'xyz' }}<br>
(A)<br>
> my A $a .=3Dnew<br>
A.new(f =3D> ->=C2=A0 { #`(Block|94272504746848) ... })<br>
> say $a.f()<br>
->=C2=A0 { #`(Block|94272504749656) ... }<br>
> say $a.f.()<br>
xyz<br>
> <br>
</p>
<p><br>
</p>
<p>I was wondering whether it was intended for `()` to return
something other than `.()`?</p>
<p>My first thought would be that `.()` would have the same
syntactic sugar as `.[]` on an Array object.</p>
<p>I looked in the Documentation and in Classes found <br>
</p>
<div><span><span><span><span><span></span></span></span></span></span><=
/div>
<div><span><span><span><span><span>=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0</span><span><span><span>&</span></=
span><span><span>!</span></span><span><span>callback</span></span></span><s=
pan>();</span></span></span></span></span></div>
<div><span><span><span><span><span>inside class Task.</span></span></sp=
an></span></span></div>
<div><span><span><span><span><span><br>
</span></span></span></span></span></div>
<div><span><span><span><span><span>So I think there may be something a =
bit wrong.
Or is this an artifact of REPL?<br>
</span></span></span></span></span></div>
</div>
</blockquote></div>
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b2gills
1/3/2021 6:59:08 PM
Hi Richard, it doesn't appear to be a REPL-only result:
user@mbook:~$ cat richard_closure.p6
class A { has &.f =3D -> { 'xyz' }};
my A $a .=3Dnew;
say $a.f();
say $a.f.();
user@mbook:~$ raku richard_closure.p6
-> { #`(Block|140238954644472) ... }
xyz
user@mbook:~$ raku --version
Welcome to =F0=9D=90=91=F0=9D=90=9A=F0=9D=90=A4=F0=9D=90=AE=F0=9D=90=9D=F0=
=9D=90=A8=E2=84=A2 v2020.10.
Implementing the =F0=9D=90=91=F0=9D=90=9A=F0=9D=90=A4=F0=9D=90=AE=E2=84=A2 =
programming language v6.d.
Built on MoarVM version 2020.10.
I took a brief glance at the StackOverflow post referred to elsewhere
in this thread, but it's unclear to me how the two issues are related.
I understood the results in the SO post to be a consequence of
declaring private methods. Further study on my part is needed.
HTH, Bill.
On Sun, Jan 3, 2021 at 10:30 AM Richard Hainsworth
<rnhainsworth@gmail.com> wrote:
>
> I was playing with classes and adding a closure to an attribute.
>
> I discovered that to call a closure on object I need `.()` rather than ju=
st `()`. See REPL below.
>
> raku
> Welcome to =F0=9D=90=91=F0=9D=90=9A=F0=9D=90=A4=F0=9D=90=AE=F0=9D=90=9D=
=F0=9D=90=A8=E2=84=A2 v2020.12.
> Implementing the =F0=9D=90=91=F0=9D=90=9A=F0=9D=90=A4=F0=9D=90=AE=E2=84=
=A2 programming language v6.d.
> Built on MoarVM version 2020.12.
>
> To exit type 'exit' or '^D'
> > class A { has &.f =3D -> { 'xyz' }}
> (A)
> > my A $a .=3Dnew
> A.new(f =3D> -> { #`(Block|94272504746848) ... })
> > say $a.f()
> -> { #`(Block|94272504749656) ... }
> > say $a.f.()
> xyz
> >
>
>
> I was wondering whether it was intended for `()` to return something othe=
r than `.()`?
>
> My first thought would be that `.()` would have the same syntactic sugar =
as `.[]` on an Array object.
>
> I looked in the Documentation and in Classes found
>
> &!callback();
> inside class Task.
>
> So I think there may be something a bit wrong. Or is this an artifact of =
REPL?
|
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perl6
1/3/2021 9:51:14 PM
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Mea culpa. Super embarrassing.
Comes from having to do something else for a year.
Thanks Brad
On 03/01/2021 18:59, Brad Gilbert wrote:
> You've already asked a similar question.
>
> https://stackoverflow.com/questions/54033524/perl6-correctly-passing-a-routine-into-an-object-variable
> <https://stackoverflow.com/questions/54033524/perl6-correctly-passing-a-routine-into-an-object-variable>
>
> When you call $a.f() you are getting the value in &!f which is a function.
>
> When you call $a.f().() you are getting the value in &!f, and then
> also calling that function.
>
> You don't need the parens on a method call if they are empty.
>
> So $a.f() is the same as $a.f
> and $a.f().() is the same as $a.f.()
>
> On Sun, Jan 3, 2021 at 12:30 PM Richard Hainsworth
> <rnhainsworth@gmail.com <mailto:rnhainsworth@gmail.com>> wrote:
>
> I was playing with classes and adding a closure to an attribute.
>
> I discovered that to call a closure on object I need `.()` rather
> than just `()`. See REPL below.
>
> raku
> Welcome to 𝐑𝐚𝐤𝐮𝐝𝐨™ v2020.12.
> Implementing the 𝐑𝐚𝐤𝐮™ programming language v6.d.
> Built on MoarVM version 2020.12.
>
> To exit type 'exit' or '^D'
> > class A { has &.f = -> { 'xyz' }}
> (A)
> > my A $a .=new
> A.new(f => -> { #`(Block|94272504746848) ... })
> > say $a.f()
> -> { #`(Block|94272504749656) ... }
> > say $a.f.()
> xyz
> >
>
>
> I was wondering whether it was intended for `()` to return
> something other than `.()`?
>
> My first thought would be that `.()` would have the same syntactic
> sugar as `.[]` on an Array object.
>
> I looked in the Documentation and in Classes found
>
> &!callback();
> inside class Task.
>
> So I think there may be something a bit wrong. Or is this an
> artifact of REPL?
>
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<p>Mea culpa. Super embarrassing.<br>
</p>
<p>Comes from having to do something else for a year.</p>
<p>Thanks Brad</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 03/01/2021 18:59, Brad Gilbert
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAD2L-T0yEEvLoAMFiwQAA6VkzWfr2hS0J7xtW0bswVt_F2zX6w@mail.gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div dir="ltr">You've already asked a similar question.
<div><br>
</div>
<div><a
href="https://stackoverflow.com/questions/54033524/perl6-correctly-passing-a-routine-into-an-object-variable"
moz-do-not-send="true">https://stackoverflow.com/questions/54033524/perl6-correctly-passing-a-routine-into-an-object-variable</a><br>
</div>
<div><br>
</div>
<div>When you call $a.f() you are getting the value in &!f
which is a function.</div>
<div><br>
</div>
<div>When you call $a.f().() you are getting the value in
&!f, and then also calling that function.</div>
<div><br>
</div>
<div>You don't need the parens on a method call if they are
empty.</div>
<div><br>
</div>
<div>So $a.f() is the same as $a.f</div>
<div>and $a.f().() is the same as $a.f.()</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Sun, Jan 3, 2021 at 12:30
PM Richard Hainsworth <<a
href="mailto:rnhainsworth@gmail.com" moz-do-not-send="true">rnhainsworth@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>
<p>I was playing with classes and adding a closure to an
attribute.</p>
<p>I discovered that to call a closure on object I need
`.()` rather than just `()`. See REPL below.</p>
<p>raku<br>
Welcome to 𝐑𝐚𝐤𝐮𝐝𝐨™ v2020.12.<br>
Implementing the 𝐑𝐚𝐤𝐮™ programming language v6.d.<br>
Built on MoarVM version 2020.12.<br>
<br>
To exit type 'exit' or '^D'<br>
> class A { has &.f = -> { 'xyz' }}<br>
(A)<br>
> my A $a .=new<br>
A.new(f => -> { #`(Block|94272504746848) ... })<br>
> say $a.f()<br>
-> { #`(Block|94272504749656) ... }<br>
> say $a.f.()<br>
xyz<br>
> <br>
</p>
<p><br>
</p>
<p>I was wondering whether it was intended for `()` to
return something other than `.()`?</p>
<p>My first thought would be that `.()` would have the same
syntactic sugar as `.[]` on an Array object.</p>
<p>I looked in the Documentation and in Classes found <br>
</p>
<div><span><span><span><span><span></span></span></span></span></span></div>
<div><span><span><span><span><span> </span><span><span><span>&</span></span><span><span>!</span></span><span><span>callback</span></span></span><span>();</span></span></span></span></span></div>
<div><span><span><span><span><span>inside class Task.</span></span></span></span></span></div>
<div><span><span><span><span><span><br>
</span></span></span></span></span></div>
<div><span><span><span><span><span>So I think there may be
something a bit wrong. Or is this an artifact of
REPL?<br>
</span></span></span></span></span></div>
</div>
</blockquote>
</div>
</blockquote>
</body>
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rnhainsworth
1/4/2021 6:51:46 PM