Thank you yary. I'm not sure we've seen any clarification on this. There's a reference to "Literal Lists" in the Perl 6 docs that looks related, but I don't have a "plain-speak" explanation for how semicolons, lists, push() and arrays inter-relate.
https://docs.perl6.org/language/list Hoping a Perl_6 guru can chime in? Thank you. --Bill. On Sun, Apr 14, 2019 at 1:26 PM yary <not....@gmail.com> wrote: > 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[dot]youtube[dot]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. >> > >> >
