6 ms·

Set in Your Ways: Perl 6’s Setty and Baggy Types

60 points by kumaranvpl 10y ago

throwaway7645 10y ago
I really like all the built-in functionality. As long as the doc is good I can live with the complexity.
- throwanem 10y ago
  Consistency of inconsistency would be nice. For example, I don't see why Set "values" should ever be exposed anywhere, since the semantics of the collection type don't include them. Seems like a great big gotcha waiting to happen.
  - gunnihinn 10y ago
    > Seems like a great big gotcha waiting to happen. In Perl? Never!
  - justinator 10y ago
    Where are they, "exposed". The post just says the values are always true and that you don't really need to care about them.
    - throwanem 10y ago
      From the post: > Set types always have True as values, and since we don’t care about iterating over Pair objects in our loop, we use the keys [function] to get just the keys of the set: the email addresses. The impression I took away from that was that you needed to make sure to pass keys(@set) rather than just @set in the operator, or else you'd get weirdness in the result. Having just installed Rakudo and fired up a REPL to find out for myself what'd happen, I find: - that my understanding from the post was erroneous - that there's some kind of weird set/string coercion going on that isn't replicable in the terms the REPL uses to describe it - that the given examples do not reliably generalize - that nothing which seems to make sense actually works - that nothing which seems to work actually makes sense - that I'm now bleeding slightly from both caruncles. Having not closely followed the Perl 6 development process, I am very glad to see it has taken on board the frequently uttered and extremely well justified criticism of Perl 5 that it's not consistent enough, and that there are so many syntactic and semantic special cases that no one who doesn't heavily specialize in the language can use it very reliably.
      - ab5tract 10y ago
        What are your expectations for reliable generalization? What were you expecting to work, in what way, that didn't work as you expected?
        throwanem 10y ago
        The Rakudo REPL apparently doesn't save history outside a session by default, so I don't have the exact details of what I was trying to do. In attempting to recreate it, though, I did manage to discover that Perl 6 "sets" appear simply to be syntactic sugar around strings split on whitespace, except when they're not, sometimes. That's not necessarily a bad thing, but why call it a type? What is it actually giving me that I can't get without having to bind and learn to use a whole new keymap full of exciting Unicode characters that I'm not a mathematician and therefore will also need to learn to identify on sight?
        ab5tract 10y ago
        I've never used a Unicode operators myself and there are no requirements to use Unicode characters. Every Unicode operator has a "Texas" counterpart in 100% ASCII. This was mentioned in the OP. I think you are mistaking `<a b c d>` with a `Set`. `< >` is a shorthand for "give me a `List` of these words" (or in this case, characters). `<a b c d>.Set` would coerce you a `Set` from that list. The set operators coerce by default, so you can pass it a list of words without requiring you to coerce it yourself beforehand.
        throwanem 10y ago
        Yeah, I cottoned to that eventually - it's short(er)-hand for Perl 5's qw() construct. I guess Set is a method (coercer!) of...lists? List-shaped things? Sets seem list-shaped, although indexing doesn't work by any syntax I could find, and certainly not by any that an @ sigil should suggest. Can I call Set on a set? Does it do something weird if I do? And if I'm going to deal with this kind of high weirdness, why not just bite the bullet and go with Haskell or even Urbit? This just feels like it's trying to out-Ruby Ruby, and Ruby is Ruby enough already. The OP had some snark to offer on the subject of "Texas" operators, and the documentation lists them by their Unicode glyphs. That they work I get. But I think it's reasonable to gather a sense of second-class citizenship from their presentation.
  - gpvos 10y ago
    In general, [Perl operators] do what you want, unless you want consistency. — man perlfunc (of Perl5)
    - throwanem 10y ago
      I thought I remembered hearing part of the idea with Perl 6 was that there'd be less of that. Apparently I have mistaken a forlorn hope for a vague memory.
zokier 10y ago
say 42 ∈ <42 55 1>; # False; ∈ operator cares about object identity As an outsider, this seems like a huge gotcha. I suppose the weirdest thing (after reading some docs) is why < > quotation is used as a set literal here. Would something like say 42 ∈ (42, 55, 1); work as expected? Or what would be the canonical way of writing an Int (not IntStr) set literal?
- labster 10y ago
  perl6 -e 'say 42 ∈ (42, 55, 1)' True That works fine -- and probably better than the quote-words operator <>. ∈ works on anything list-like, not just set types.
- sp332 10y ago
  The angle brackets are explicitly string operators. So the set contains the string "42" but not the number 42. Perl does generally have different operators for strings vs numbers, so that's something you'd be used to thinking about already. Probably not a huge gotcha. Edit: these things are weird though. https://docs.perl6.org/type/IntStr https://docs.perl6.org/type/IntStr
- ab5tract 10y ago
  To clarify, it isn't being used as a set literal. It's a list passed to an operator that happily coerces your lists to sets. Allomorphs are tricky things, but I think it was the right decision to treat them separately in collections. `Set.new(42, 55, 1)` is the most formal way to create a new set, but Perl 6 provides `set(42, 55, 1)` as a shorthand.
dscpls 10y ago
One of the best punny titles I've ever heard. Well done. Really well done.
andrewpk 10y ago
those hyper operators...
bshimmin 10y ago
I stared at .put for @wanted.combinations.grep: { $materials ≽ [⊎] |$^stuff-we-want }; and the preceding lines for some time, and then read the description, clicked through a few of the links on the different operators and read the explanations of those, and then I finally understood what was happening here. I worry, though, that at this point in my life I would either 1) never be able to remember all this stuff; 2) even if I could remember it, never be in a position where it would dawn on me that whatever I was trying to do was a good fit for it.
- smitherfield 10y ago
  Yeah, as someone whose go to languages are C++, Scala and Ruby[1], it's awesome that Perl 6 does so much[2], but I think I'd have a hard time keeping track of it all. [1] Meaning I like having lots of features in my toolbox. [2] And, amazingly, Rakudo is a pretty compact executable compared to most other langs.
jlarocco 10y ago
Every Perl6 article I read makes it even less likely that I'll ever use it. It's so ugly, with so many arcane things to remember, with so many weird naming conventions that just don't make any sense to me. > We intersected two sets with the ∩, U+2229 INTERSECTION, intersection operator and received a set that contains only the elements present in both original sets. I'm not against having built-in Unicode operators, but the non-Unicode version should be the name of the character. What's the non-Unicode version of "∩"? Obviously it's "(&)"! Good thing there are only 57 of them to remember! I tried to enter "∩" just now in Emacs: (ctrl-x, 8, enter, i, n, t, tab, r, tab, s, e, c, tab). It would have been shorter to just type "intersection"... And why is that called the "Texas" version?
- cygx 10y ago
  What's the non-Unicode version of "∩"? Obviously it's "(&)"! I find that pretty obvious, actually. After all A ∩ B = { x ∈ A & x ∈ B }
  - jlarocco 10y ago
    That at least explains where it comes from, but I'd still argue it won't be obvious to people at first. And it's still kind of confusing. If the goal is to match math notation then wouldn't (^) or (+) make more sense? A ∩ B = { x ∈ A ∧ x ∈ B }
    - cygx 10y ago
      If the goal is to match math notation then wouldn't (^) or (+) make more sense? Not necessarily. & is the ASCII symbol associated with logical 'and' that most programming languages have settled on, including Perl6, so for internal consistency, it makes sense to use it. Also note that the ampersand, while pretty rare, is sometimes used for that purpose in mahematical notation (https://en.wikipedia.org/wiki/List_of_logic_symbols https://en.wikipedia.org/wiki/List_of_logic_symbols).
- MichaelBurge 10y ago
  > What's the non-Unicode version of "∩"? Obviously it's "(&)"! That convention has decades of precedence in programming: int bitset_a = 0x01234567, bitset_b = 0x89ABCDEF; int bitset_c = bitset_a & bitset_b; And at least a century in math.

60 points by kumaranvpl 10y ago

throwaway7645 10y ago

I really like all the built-in functionality. As long as the doc is good I can live with the complexity.

throwanem 10y ago
Consistency of inconsistency would be nice. For example, I don't see why Set "values" should ever be exposed anywhere, since the semantics of the collection type don't include them. Seems like a great big gotcha waiting to happen.
- gunnihinn 10y ago
  > Seems like a great big gotcha waiting to happen. In Perl? Never!
- justinator 10y ago
  Where are they, "exposed". The post just says the values are always true and that you don't really need to care about them.
  - throwanem 10y ago
    From the post: > Set types always have True as values, and since we don’t care about iterating over Pair objects in our loop, we use the keys [function] to get just the keys of the set: the email addresses. The impression I took away from that was that you needed to make sure to pass keys(@set) rather than just @set in the operator, or else you'd get weirdness in the result. Having just installed Rakudo and fired up a REPL to find out for myself what'd happen, I find: - that my understanding from the post was erroneous - that there's some kind of weird set/string coercion going on that isn't replicable in the terms the REPL uses to describe it - that the given examples do not reliably generalize - that nothing which seems to make sense actually works - that nothing which seems to work actually makes sense - that I'm now bleeding slightly from both caruncles. Having not closely followed the Perl 6 development process, I am very glad to see it has taken on board the frequently uttered and extremely well justified criticism of Perl 5 that it's not consistent enough, and that there are so many syntactic and semantic special cases that no one who doesn't heavily specialize in the language can use it very reliably.
    - ab5tract 10y ago
      What are your expectations for reliable generalization? What were you expecting to work, in what way, that didn't work as you expected?
      - throwanem 10y ago
        The Rakudo REPL apparently doesn't save history outside a session by default, so I don't have the exact details of what I was trying to do. In attempting to recreate it, though, I did manage to discover that Perl 6 "sets" appear simply to be syntactic sugar around strings split on whitespace, except when they're not, sometimes. That's not necessarily a bad thing, but why call it a type? What is it actually giving me that I can't get without having to bind and learn to use a whole new keymap full of exciting Unicode characters that I'm not a mathematician and therefore will also need to learn to identify on sight?
        ab5tract 10y ago
        I've never used a Unicode operators myself and there are no requirements to use Unicode characters. Every Unicode operator has a "Texas" counterpart in 100% ASCII. This was mentioned in the OP. I think you are mistaking `<a b c d>` with a `Set`. `< >` is a shorthand for "give me a `List` of these words" (or in this case, characters). `<a b c d>.Set` would coerce you a `Set` from that list. The set operators coerce by default, so you can pass it a list of words without requiring you to coerce it yourself beforehand.
        throwanem 10y ago
        Yeah, I cottoned to that eventually - it's short(er)-hand for Perl 5's qw() construct. I guess Set is a method (coercer!) of...lists? List-shaped things? Sets seem list-shaped, although indexing doesn't work by any syntax I could find, and certainly not by any that an @ sigil should suggest. Can I call Set on a set? Does it do something weird if I do? And if I'm going to deal with this kind of high weirdness, why not just bite the bullet and go with Haskell or even Urbit? This just feels like it's trying to out-Ruby Ruby, and Ruby is Ruby enough already. The OP had some snark to offer on the subject of "Texas" operators, and the documentation lists them by their Unicode glyphs. That they work I get. But I think it's reasonable to gather a sense of second-class citizenship from their presentation.
- gpvos 10y ago
  In general, [Perl operators] do what you want, unless you want consistency. — man perlfunc (of Perl5)
  - throwanem 10y ago
    I thought I remembered hearing part of the idea with Perl 6 was that there'd be less of that. Apparently I have mistaken a forlorn hope for a vague memory.

zokier 10y ago

say 42 ∈ <42 55 1>; # False; ∈ operator cares about object identity As an outsider, this seems like a huge gotcha. I suppose the weirdest thing (after reading some docs) is why < > quotation is used as a set literal here. Would something like say 42 ∈ (42, 55, 1); work as expected? Or what would be the canonical way of writing an Int (not IntStr) set literal?

labster 10y ago
perl6 -e 'say 42 ∈ (42, 55, 1)' True That works fine -- and probably better than the quote-words operator <>. ∈ works on anything list-like, not just set types.
sp332 10y ago
The angle brackets are explicitly string operators. So the set contains the string "42" but not the number 42. Perl does generally have different operators for strings vs numbers, so that's something you'd be used to thinking about already. Probably not a huge gotcha. Edit: these things are weird though. https://docs.perl6.org/type/IntStr https://docs.perl6.org/type/IntStr
ab5tract 10y ago
To clarify, it isn't being used as a set literal. It's a list passed to an operator that happily coerces your lists to sets. Allomorphs are tricky things, but I think it was the right decision to treat them separately in collections. `Set.new(42, 55, 1)` is the most formal way to create a new set, but Perl 6 provides `set(42, 55, 1)` as a shorthand.

dscpls 10y ago

One of the best punny titles I've ever heard. Well done. Really well done.

andrewpk 10y ago

those hyper operators...

bshimmin 10y ago

I stared at .put for @wanted.combinations.grep: { $materials ≽ [⊎] |$^stuff-we-want }; and the preceding lines for some time, and then read the description, clicked through a few of the links on the different operators and read the explanations of those, and then I finally understood what was happening here. I worry, though, that at this point in my life I would either 1) never be able to remember all this stuff; 2) even if I could remember it, never be in a position where it would dawn on me that whatever I was trying to do was a good fit for it.

smitherfield 10y ago
Yeah, as someone whose go to languages are C++, Scala and Ruby[1], it's awesome that Perl 6 does so much[2], but I think I'd have a hard time keeping track of it all. [1] Meaning I like having lots of features in my toolbox. [2] And, amazingly, Rakudo is a pretty compact executable compared to most other langs.

jlarocco 10y ago

Every Perl6 article I read makes it even less likely that I'll ever use it. It's so ugly, with so many arcane things to remember, with so many weird naming conventions that just don't make any sense to me. > We intersected two sets with the ∩, U+2229 INTERSECTION, intersection operator and received a set that contains only the elements present in both original sets. I'm not against having built-in Unicode operators, but the non-Unicode version should be the name of the character. What's the non-Unicode version of "∩"? Obviously it's "(&)"! Good thing there are only 57 of them to remember! I tried to enter "∩" just now in Emacs: (ctrl-x, 8, enter, i, n, t, tab, r, tab, s, e, c, tab). It would have been shorter to just type "intersection"... And why is that called the "Texas" version?

cygx 10y ago
What's the non-Unicode version of "∩"? Obviously it's "(&)"! I find that pretty obvious, actually. After all A ∩ B = { x ∈ A & x ∈ B }
- jlarocco 10y ago
  That at least explains where it comes from, but I'd still argue it won't be obvious to people at first. And it's still kind of confusing. If the goal is to match math notation then wouldn't (^) or (+) make more sense? A ∩ B = { x ∈ A ∧ x ∈ B }
  - cygx 10y ago
    If the goal is to match math notation then wouldn't (^) or (+) make more sense? Not necessarily. & is the ASCII symbol associated with logical 'and' that most programming languages have settled on, including Perl6, so for internal consistency, it makes sense to use it. Also note that the ampersand, while pretty rare, is sometimes used for that purpose in mahematical notation (https://en.wikipedia.org/wiki/List_of_logic_symbols https://en.wikipedia.org/wiki/List_of_logic_symbols).
MichaelBurge 10y ago
> What's the non-Unicode version of "∩"? Obviously it's "(&)"! That convention has decades of precedence in programming: int bitset_a = 0x01234567, bitset_b = 0x89ABCDEF; int bitset_c = bitset_a & bitset_b; And at least a century in math.