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

https://perl6advent.wordpress.com/2016/12/07/set-in-your-ways-perl-6s-setty-and-baggy-types/

by kumaranvpl • 10 years ago

60 34 10 years ago

perl6advent.wordpress.com

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

throwanem7• 10 years 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• 10 years ago

Seems like a great big gotcha waiting to happen.

In Perl? Never!

justinator• 10 years 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.

gpvos• 10 years ago

In general, [Perl operators] do what you want, unless you want consistency. — man perlfunc (of Perl5)

zokier• 10 years 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?

labster2• 10 years 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• 10 years 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

ab5tract4• 10 years 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• 10 years ago

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

andrewpk• 10 years ago

those hyper operators...

bshimmin• 10 years 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• 10 years 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.

jlarocco2• 10 years 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?

cygx2• 10 years 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 }

jlarocco2• 10 years 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 }

MichaelBurge• 10 years 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.

CIAvash• 10 years ago

There is a doc for entering unicode characters: https://docs.perl6.org/language/unicode_entry.html

It also has an Emacs section. For a more detailed explanation for Emacs see my blog post: https://blog.ciavash.name/2016/01/09/entering-perl6-unicode-...

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

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