Re^2: [Perl 6] Object methods on the fly?

[TimToady]

You're on the right track. You want something like:

    @array does role {
        method insert ($x) {
            @.push($x) unless any(self) eqv $x;
        }
    }

Arguably we could provide syntactic sugar to reduce that to:

    @array does method insert ($x) {
        @.push($x) unless any(self) eqv $x;
    }

Perhaps that use of does is redundant with but= and could be removed, but it does read better, I think. In any case, doing an operation like this on an object ends up creating an anonymous class that derives from the original class and adds in the extra method, so you don't clobber the original Array class.

[blazar]

    @array does role {
        method insert ($x) {
            @.push($x) unless any(self) eqv $x;
        }
    }

Whoa! And it evens runs on Pugs:

pugs> my @array does role {
....> method insert ($x) { @.push($x) if none(self) eqv $x }
....> }
()
pugs> my @array=(1..5);
pugs> @array.insert($_) for 1,2,6;
pugs> say @array
123456
Bool::True

BTW: Could I put the initialization in the definition too? I tried with

pugs> my @array does role {
....> method insert ($x) { @.push($x) if none(self) eqv $x }
....> } = (1..5);
(1, 2, 3, 4, 5)

and it works, but it doesn't with the assignment directly to the right of @array, OTOH I'm sure most people would find it to be more intuitive, while this way they would just say: "for clarity, initialize it in a separate statement."

BTW: why doesn't the following work, instead?

pugs> my @array does role {
....>     multi method insert ($x) { @.push($x) if none(self) eqv $x }
....>     multi method insert (@x) { @.insert($_) for @x }
....> } = 1..5;
(1, 2, 3, 4, 5)
pugs> @array.insert(3..7);
pugs> say @array
1234534567
Bool::True

(If I use *@x, pugs "hangs", instead.)

BTW: (the last, really!) what is self supposed to be? After all no suitable and short enough variable/pronoun was found? The following is all that pugs can tell me:

pugs> self
macro {Prim ([Pugs.AST.Internals.Val] -> Pugs.AST.Eval.Eval Pugs.AST.I
+nternals.Val)}

Update: Two of the questions asked here were reposted in separate new threads in

• [Perl 6] Problem with multi methods
• [Perl 6] Initialization within complex declarations

[TimToady]

self is just a built-in function returning the invocant. If you want a different name for it, you can always declare it explicitly.

Also, it's probably bogus to say any(self). It should probably be a function that is not context sensitive, in which case we'd have to say any(self[]) or some such to pull out the elements.

Finally, I think the failure of the multi form is just hitting some things that aren't completely implemented in pugs yet.