On Tue, Feb 05, 2008 at 11:57:37AM -0800, Jonathan Lang wrote: : Larry Wall wrote: : > : Is it forbidden to use placeholder parameters in conjunction with : > : "my"? Or would it simply not do anything useful? I ask because "Do : > : what I mean" would seem to imply that 'my Dog $^foo' would specify : > : $^foo's type as 'Dog'. Though if you start doing too much of that, : > : you're almost certainly better off explicitly defining a signature. : > : > Indeed. : : So we're agreed that it could be abused if permitted. Still, is it permitted?
No. The only twigils currently permitted in a signature (and what follows a declarator is a signature even if it doesn't look like it) are "." and "!". I don't see a good case for relaxing this. I don't think we should allow a "my" to retroactively override a parameter's type in any case. : > : Also, how much trouble would we get in if we spelled the ubiquitous : > : alias for a method's invocant as C< $^_ > instead of C< $self >? : > : > Then we're back to confusing people over the difference between the : > object and the topic, and the topic-as-self breaks as soon as you : > topicalize some other way. And you can always throw in a "$_ := self" : > or a "given self" if you really want it. Plus $.foo is still only : > one character longer than .foo so it doesn't really get you much most : > of the time. : : Huh. My intention was not to topicalize the invocant. Rather, I : thought that $_ and $^_ would be treated as two separate variables: $_ : would be the topic, while $^_ would be the invocant. I'm trying to : think of why this distinction might not be. Right now the placeholder twigils are specced in terms of rewrite rules to twigil-less signatures, so the real variables never actually carry the twigil. Therefore $^foo and $foo are the same underlying variable as it currently stands, just as $+foo really maps to a contextual variable name somewhere that has no '+' as part of its name. Note also that $!foo and $foo are likewise really the same variable within a method. The $! form is just more emphatically private. : Unless I'm missing something, it would be very much like what we have : now, except that '$self' would be spelled '$^_' (shorter and not tied : to English, but instead evocative of "I'm using a parameter that I may : not have declared in the signature, sort of like what placeholder : parameters do" and "I'm using the parameter that defines what this : routine is talking about, sort of like what the topic variable does"). There is no $self, it's just the 0-ary function "self". There is only a variable if you specify it explicitly as the invocant in a signature. Besides $^_ is just uglier than anything else I've seen today... Larry
