In the hope this saves Allison time, and/or
clarifies things for me, I'll attempt some
answers.
> In your article at perl.com you describes
> various ways and situations when perl
> creates a topic and this is described as
> perl making the following binding on my behalf:
>
> $_ := $some_var ; *1*
Well, $_ might not be bound to a named variable
but instead be just set to a value, or it might
be bound to an array cell or some other unnamed
container.
> is *1* _all_ that topic is about ?
Sorta. To quote an excellent summary:
"Topic is $_".
> my $x,$z;
> given $x->$y {
> $_ := $z ;
> when 2 { ... } #checks against $z ???
> }
Yes.
> methods topicalize their invocant. Is $self
> aliased to $_ inside the method in this ex. ?
>
> method sub_ether ($self: $message) {
> .transmit( .encode($message) );
> }
Yes.
> will it be an error to write
> method sub_ether ($self: $message, $x is topic) {...}
No.
> what happens if I write
> method sub_ether ($self: $message) {
> $_ := $message ;
> }
> or
>
> method sub_ether ($self: $message) {
> $_ = $message ;
> }
Both Ok. $_ is "it" and has the value $message;
in the former case $_ and $message are bound.
> is $_ always lexical variable.
Yes.
> Or I can have $MyPackage::_ ?
You can copy or alias any value.
> * can I alias $something to $_ ?
> $something := $_
Sure. Because...
> (it seems that I can , because $_ is just
> another variable )
> $b := $a ;
> $c := $b ;
>
> ( now changing value of one variable will
> change other two ??? )
Yes.
> or e.g.
>
> $a = 1 ;
> $Z = 10 ;
>
> $b := $a ;
> $c := $b ;
>
> print $c # prints 1
> $a := $Z ;
> print $c # prints 10
> $a = 5;
> print $Z # prints 5
Yes.
> also
>
> @a := ( $a, $b)
Er, I don't think (it makes sense that) you
can bind to a literal.
> $b := $c
> @a[1] = 10 ;
> print $c # prints 10
Lost you there, even ignoring the literal issue.
--
ralph
