Looks like perl6 semicolon has different meaning in a list vs a capture. In
a list, it "makes sense to me"
> perl6 --version
This is Rakudo Star version 2018.10 built on MoarVM version 2018.10
implementing Perl 6.c.
>perl6
To exit type 'exit' or '^D'
> ('a').perl
"a"
> ('a';).perl
"a"
> ('a', 'b' ;).perl
("a", "b")
> ('a', 'b' ; 'c').perl
(("a", "b"), "c")
> ('a', 'b' ; 'c' ;).perl
(("a", "b"), "c")
> ('a', 'b' ; 'c' ; ;).perl
(("a", "b"), "c", Nil)
> ('a', 'b' ; 'c' , ; ;).perl
(("a", "b"), ("c",), Nil)
- the rule "a single thing is a scalar, a single thing followed by a comma
is a list" applies in the last example
But there's inconsistency with captures.
>\('a').perl
\("a")
> \('a';).perl; # Unexpected empty list at end
\(("a",), ())
> \('a', 'b' ;).perl; # Unexpected empty list at end
\(("A", "b"), ())
> \('a', 'b' ; 'c').perl; # unexpected "c" as list
\(("a", "b"), ("c",))
> \('a', 'b' ; 'c' ;).perl; # "c" as list, and empty list at end
\(("a", "b"), ("c",), ())
> \('a', 'b' ; 'c' ; ;).perl; # "c" as list, and 2 empty lists instead of
single nil at end
\(("a", "b"), ("c",), (), ())
> \('a', 'b' ; 'c' , ; ;).perl; # 2 empty lists instead of single nil at end
\(("a", "b"), ("c",), (), ())
This cries for an explanation, or a bug report.
-y
On Sun, Apr 14, 2019 at 11:57 AM Joseph Brenner <doom...@gmail.com> wrote:
> Just in case it wasn't clear from Bill's discussion, I think the
> reason this case seems weird is normally we expect trailing separators
> to be ignored, as with the extra comma here:
>
> > my @monsters = ('ghidora', 'mothera', 'wolfman', 'zuckerberg',);
> [ghidora mothera wolfman zuckerberg]
>
> If you do this, and type in a trailing semi-colon in the wrong place,
> you stumble across some odd behavior:
>
> > @monsters.push('tingler';)
> [ghidora mothera wolfman zuckerberg (tingler) ()]
>
> It seems a bit LTA, though it might be unavoidable because this is valid:
>
> my @monsters = ('ghidora', 'mothera'; 'frankenstein',
> 'wolfman';'purple-people-eater')
> [(ghidora mothera) (frankenstein wolfman) purple-people-eater]
>
> Though even here, the behavior seems a bit strange, because
> "purple-people-eater" ended up as an element in the top-level list.
> Hm, no empty list is appended if you do this:
>
> my @monsters = ('ghidora', 'mothera'; 'frankenstein', 'wolfman';)
> [(ghidora mothera) (frankenstein wolfman)]
>
> But the push method seems to interpret it differently:
>
> @monsters.push('purple-people-eater';)
> [(ghidora mothera) (frankenstein wolfman) (purple-people-eater) ()]
>
>
>
> On 4/14/19, William Michels via perl6-users <perl6-us...@perl.org> wrote:
> > Hello,
> >
> > I've been working through Patrick Michaud's excellent videos from the
> > The Perl Conference 2016. At about 35:45 of the following 2016 video
> > (Part 1 of 2), Patrick discusses arrays:
> >
> > https://www.youtube.com/watch?v=ySch4xpoPA0
> >
> > At this point in the video, Patrick also discusses push() and pop()
> > calls on arrays. For practice I tried pushing and popping strings in
> > the REPL. However, I discovered an unusual property when I misplaced a
> > semicolon during call to push(). See what happens below when a
> > semicolon is included within the parentheses of push():
> >
> > "This is Rakudo version 2018.12 built on MoarVM version 2018.12
> > implementing Perl 6.d."
> >
> >> my @countries = "UK", "Spain", "Slovakia", "Sweden";
> > [UK Spain Slovakia Sweden]
> >> @countries.push("Finland");
> > [UK Spain Slovakia Sweden Finland]
> >> my @countries = "UK", "Spain", "Slovakia", "Sweden";
> > [UK Spain Slovakia Sweden]
> >> @countries.push("Finland";)
> > [UK Spain Slovakia Sweden (Finland) ()]
> >> my @countries = "UK", "Spain", "Slovakia", "Sweden";
> > [UK Spain Slovakia Sweden]
> >> @countries.push("Finland";);
> > [UK Spain Slovakia Sweden (Finland) ()]
> >
> > Misplacing a semicolon within the push() call adds two elements to the
> > array. When I examine these two elements, I see that they are both
> > "List" elements:
> >
> >> @countries[3].WHAT
> > (Str)
> >> @countries[4].WHAT
> > (List)
> >> @countries[5].WHAT
> > (List)
> >
> > Apparently, multiple semicolons within push() will add multiple list
> > elements to the end of the intended array:
> >
> >> my @countries = "UK", "Spain", "Slovakia", "Sweden";
> > [UK Spain Slovakia Sweden]
> >> @countries.push("Finland";;);
> > [UK Spain Slovakia Sweden (Finland) () ()]
> >> my @countries = "UK", "Spain", "Slovakia", "Sweden";
> > [UK Spain Slovakia Sweden]
> >> @countries.push(;;;;;;;);
> > [UK Spain Slovakia Sweden () () () () () () () ()]
> >
> > It is surprising to me that "List" elements are appended to the array
> > with push() as described above. If one tries to add one or more
> > elements via indexing and there 'aren't enough elements' so to speak
> > (by accident or design), the array grows by inserting "Any" elements,
> > not "List" elements:
> >
> >> my @countries = "UK", "Spain", "Slovakia", "Sweden";
> > [UK Spain Slovakia Sweden]
> >> @countries[5] = "Finland";
> > Finland
> >> say @countries
> > [UK Spain Slovakia Sweden (Any) Finland]
> >>
> >> my @countries = "UK", "Spain", "Slovakia", "Sweden";
> > [UK Spain Slovakia Sweden]
> >> @countries[6..7] = "Finland", "Norway";
> > (Finland Norway)
> >> say @countries
> > [UK Spain Slovakia Sweden (Any) (Any) Finland Norway]
> >
> > I've briefly checked pop() to see if there are similar issues, but 1)
> > placing a string within the parentheses of pop() will throw an error,
> > and 2) placing a semicolon within the parentheses of pop() will throw
> > an error. However, these error message are slightly different. A
> > string argument to pop() will result in an error that says "Too many
> > positionals passed; expected 1 argument but got 2" while a semicolon
> > argument to pop() will result in an error that says "Too many
> > positionals passed; expected 1 argument but got 3".
> >
> >> my @countries = "UK", "Spain", "Slovakia", "Sweden";
> > [UK Spain Slovakia Sweden]
> >> @countries.pop("Finland")
> > Too many positionals passed; expected 1 argument but got 2
> > in block <unit> at <unknown file> line 1
> >
> >> @countries.pop(;)
> > Too many positionals passed; expected 1 argument but got 3
> > in block <unit> at <unknown file> line 1
> >
> >>
> >
> >
> > Any help appreciated,
> >
> > Bill.
> >
> > William Michels, Ph.D.
> >
> > PS Thanks to Joe Brenner for talking over this Perl6 code with me.
> >
>
