4 ms·

So basically == is overloaded to also be an operator which means "intersects". I mean, it's nice that this sort of functionality has nice and concise operators

So basically == is overloaded to also be an operator which means "intersects". I mean, it's nice that this sort of functionality has nice and concise operators, but I'm coming from a school of thought where overloading the equality operator should not be done lightly :)

masklinn 11y ago
> So basically == is overloaded to also be an operator which means "intersects". Junctions seem way more complex than that, first there are 4 different junction contains (any, all, one and none), second they overload 12 comparison operators each and third the other operand doesn't have to be a junction. So e.g. any(@ar1) == any(@ar2) is an intersection but any(@ar1) == $val is a containment, and I've no idea what all(@ar1) < any(@ar2) would be, I guess it would check that max(ar1) < max(ar2)?
- senekerim 11y ago
  This looks awful to my (mathematically trained) eyes. What is the rationale behind introducing this language feature?
  - masklinn 11y ago
    I really couldn't tell you. I guess "it's perl, we can"?
  - hahainternet 11y ago
    Could you explain why you think this is awful? Perl 6 has proper sets, bags and the appropriate operators for 'normal' set operations too.
  - raiph 11y ago
    One that I recall that I'm hoping still applies is having a syntactically and conceptually lightweight way to express semantically parallel computation logic. Given the code: junction1 = val1 | val2 | val3; junction2 = val4 & val5; if junction1 op junction2 { ... }; the compiler is free to fire off several threads, or set up a lower level SIMD parallel process, with short-circuiting, to compute the conditional result.
  - awwaiid 11y ago
    * Seems kinda cool * Makes $x == 5|6 look kinda cool * $string ~~ /<first>/ & /<second>/ & /<third>/ # matches all three regexes. huh. kinda cool * (5|6).foo maybe we can do that in cpu-parallel (it doesn't now)? That might be kinda cool * sub is-prime($n where $n > 2) { $n % none(2..sqrt($n)) == 0 } # Logical O(1) prime test if only you had that quantum-coprocessor? That... would be kinda cool * ... you might notice a pattern to the motivation for this feature :)
- Estragon 11y ago
  no idea what all(@ar1) < any(@ar2) would be Subset?
  - raiph 11y ago
    I think that means something like all the individual values in the @ar1 list of values are less than at least one of the individual values in @ar2.
    - awwaiid 11y ago
      Yes exactly. To take the code snippet a cousin-reply mentioned one step further, swaping @a and @b: > my @a = <1 2 3 4>; [1 2 3 4] > my @b = <2 3>; [2 3] > say so all(@a) < any(@b); False > say so all(@b) < any(@a); True
- hahainternet 11y ago
  > I've no idea what all(@ar1) < any(@ar2) would be, I guess it would check that max(ar1) < max(ar2)? It seems that it just expands the lists using the operator. The output from junctions is quite nice: > my @a = <1 2 3 4>; > my @b = <2 3>; > say all(@a) < any(@b); all(any(True, True), any(False, True), any(False, False), any(False, False)) > say so all(@a) < any(@b); False
raiph 11y ago
I'm very much not sure of the following but I'm going to say it anyway and let folk explain how I'm wrong. :) Each operator and its overloads -- certainly built ins, users are recommended to follow suit -- conceptually maintains its own single high level semantics. Thus, while some langs have a `+` op that does numeric addition or string concat based on operand types, in Perl 6 a `+` will always mean numeric addition (unless a user breaks this convention). `==` is always numeric value equality. `==` does what most folk would expect between any pair of values that are a subclass of Any (the root of the type hierarchy for most purposes). Junction is a direct subclass of Mu (the ultimate root of the type hierarchy), outside the Any hierarchy. When a scalar operation is applied to one or more Junction values, the relevant operation is "autothreaded" over the superposed values inside the Junctions and returns a new Junction value. If a Junction is treated as a boolean the Junction collapses to a regular single boolean value.
mst 11y ago
If operator overloading in perl6 was like operator overloading in most languages, that would be a very valid school of thought. Thing is, operators in perl6 are basically multimethods under the hood, as is pretty much everything else - so it's a much saner, more predictable thing than, say, the bag of razorblades that is perl5 overloading (which I've used to good effect, but, still, razorblades ;).
- deleted 11y ago
  [deleted]

masklinn 11y ago

> So basically == is overloaded to also be an operator which means "intersects". Junctions seem way more complex than that, first there are 4 different junction contains (any, all, one and none), second they overload 12 comparison operators each and third the other operand doesn't have to be a junction. So e.g. any(@ar1) == any(@ar2) is an intersection but any(@ar1) == $val is a containment, and I've no idea what all(@ar1) < any(@ar2) would be, I guess it would check that max(ar1) < max(ar2)?

senekerim 11y ago
This looks awful to my (mathematically trained) eyes. What is the rationale behind introducing this language feature?
- masklinn 11y ago
  I really couldn't tell you. I guess "it's perl, we can"?
- hahainternet 11y ago
  Could you explain why you think this is awful? Perl 6 has proper sets, bags and the appropriate operators for 'normal' set operations too.
- raiph 11y ago
  One that I recall that I'm hoping still applies is having a syntactically and conceptually lightweight way to express semantically parallel computation logic. Given the code: junction1 = val1 | val2 | val3; junction2 = val4 & val5; if junction1 op junction2 { ... }; the compiler is free to fire off several threads, or set up a lower level SIMD parallel process, with short-circuiting, to compute the conditional result.
- awwaiid 11y ago
  * Seems kinda cool * Makes $x == 5|6 look kinda cool * $string ~~ /<first>/ & /<second>/ & /<third>/ # matches all three regexes. huh. kinda cool * (5|6).foo maybe we can do that in cpu-parallel (it doesn't now)? That might be kinda cool * sub is-prime($n where $n > 2) { $n % none(2..sqrt($n)) == 0 } # Logical O(1) prime test if only you had that quantum-coprocessor? That... would be kinda cool * ... you might notice a pattern to the motivation for this feature :)
Estragon 11y ago
no idea what all(@ar1) < any(@ar2) would be Subset?
- raiph 11y ago
  I think that means something like all the individual values in the @ar1 list of values are less than at least one of the individual values in @ar2.
  - awwaiid 11y ago
    Yes exactly. To take the code snippet a cousin-reply mentioned one step further, swaping @a and @b: > my @a = <1 2 3 4>; [1 2 3 4] > my @b = <2 3>; [2 3] > say so all(@a) < any(@b); False > say so all(@b) < any(@a); True
hahainternet 11y ago
> I've no idea what all(@ar1) < any(@ar2) would be, I guess it would check that max(ar1) < max(ar2)? It seems that it just expands the lists using the operator. The output from junctions is quite nice: > my @a = <1 2 3 4>; > my @b = <2 3>; > say all(@a) < any(@b); all(any(True, True), any(False, True), any(False, False), any(False, False)) > say so all(@a) < any(@b); False

raiph 11y ago

I'm very much not sure of the following but I'm going to say it anyway and let folk explain how I'm wrong. :) Each operator and its overloads -- certainly built ins, users are recommended to follow suit -- conceptually maintains its own single high level semantics. Thus, while some langs have a `+` op that does numeric addition or string concat based on operand types, in Perl 6 a `+` will always mean numeric addition (unless a user breaks this convention). `==` is always numeric value equality. `==` does what most folk would expect between any pair of values that are a subclass of Any (the root of the type hierarchy for most purposes). Junction is a direct subclass of Mu (the ultimate root of the type hierarchy), outside the Any hierarchy. When a scalar operation is applied to one or more Junction values, the relevant operation is "autothreaded" over the superposed values inside the Junctions and returns a new Junction value. If a Junction is treated as a boolean the Junction collapses to a regular single boolean value.

mst 11y ago

If operator overloading in perl6 was like operator overloading in most languages, that would be a very valid school of thought. Thing is, operators in perl6 are basically multimethods under the hood, as is pretty much everything else - so it's a much saner, more predictable thing than, say, the bag of razorblades that is perl5 overloading (which I've used to good effect, but, still, razorblades ;).

deleted 11y ago
[deleted]