4 ms·

Scala Traits

51 points by harlock81 13y ago

deleted 13y ago
[deleted]
- x3ro 13y ago
  What did you expect it to print, and why, if I may ask?
  - lmm 13y ago
    I expected it to print "B", because D is visually closer to B so it would make more sense to me for it to be biased in that direction. (I was quite conscious that I was guessing, and wouldn't have written code depending on my assumption without testing it first)
    - harlock81 13y ago
      The behavior you get is because of class linearization: this article explains it quite clearly: https://code.google.com/p/scala-discovery/wiki/Linearization https://code.google.com/p/scala-discovery/wiki/Linearization
    - x3ro 13y ago
      I'm not quite sure what you mean by "visually" closer. Do you mean the actual distance in characters between "class D" and "with B"? Intuitively, I expected the compiler to first add the "B" trait, and then the "C" trait, which overwrites what was previously added by the "B" trait. But this seems to be much more subjective that I would've thought, apparently ;)
      - lmm 13y ago
        >Do you mean the actual distance in characters between "class D" and "with B"? Yes, exactly that.
leothekim 13y ago
Artima wrote an article describing how the use of traits (along with other scala features) can contribute to increased compile times.[1] FTFA: "... the compile time cost of mixing in a trait compared to extending a superclass likely exists because the compiler must insert forwarding methods for all the methods declared in the trait into the body of the subclass when mixing in, but when extending a superclass it does not. Instead, the subclass simply inherits the superclass implementations of those methods. We did observe that the larger the number of methods to be mixed in the more the compile time was increased." [1] http://www.artima.com/articles/compile_time.html http://www.artima.com/articles/compile_time.html
gtani 13y ago
Good article, (need to work on colorizing REPL output tho) Here's a Cake Pattern and type class followups: Slides https://speakerdeck.com/marakana/ne-scala-2012-the-typeclass-pattern-an-alternative-to-inheritance https://speakerdeck.com/marakana/ne-scala-2012-the-typeclass... https://dl.dropbox.com/u/1679797/NE%20Scala/Bakery%20from%20the%20Black%20Lagoon.pdf https://dl.dropbox.com/u/1679797/NE%20Scala/Bakery%20from%20... videos of above: http://marakana.com/s/post/1397/2013_northeast_scala_symposium_videos http://marakana.com/s/post/1397/2013_northeast_scala_symposi...

Scala Traits

51 points by harlock81 13y ago

deleted 13y ago

[deleted]

x3ro 13y ago
What did you expect it to print, and why, if I may ask?
- lmm 13y ago
  I expected it to print "B", because D is visually closer to B so it would make more sense to me for it to be biased in that direction. (I was quite conscious that I was guessing, and wouldn't have written code depending on my assumption without testing it first)
  - harlock81 13y ago
    The behavior you get is because of class linearization: this article explains it quite clearly: https://code.google.com/p/scala-discovery/wiki/Linearization https://code.google.com/p/scala-discovery/wiki/Linearization
  - x3ro 13y ago
    I'm not quite sure what you mean by "visually" closer. Do you mean the actual distance in characters between "class D" and "with B"? Intuitively, I expected the compiler to first add the "B" trait, and then the "C" trait, which overwrites what was previously added by the "B" trait. But this seems to be much more subjective that I would've thought, apparently ;)
    - lmm 13y ago
      >Do you mean the actual distance in characters between "class D" and "with B"? Yes, exactly that.

leothekim 13y ago

Artima wrote an article describing how the use of traits (along with other scala features) can contribute to increased compile times.[1] FTFA: "... the compile time cost of mixing in a trait compared to extending a superclass likely exists because the compiler must insert forwarding methods for all the methods declared in the trait into the body of the subclass when mixing in, but when extending a superclass it does not. Instead, the subclass simply inherits the superclass implementations of those methods. We did observe that the larger the number of methods to be mixed in the more the compile time was increased." [1] http://www.artima.com/articles/compile_time.html http://www.artima.com/articles/compile_time.html

gtani 13y ago

Good article, (need to work on colorizing REPL output tho) Here's a Cake Pattern and type class followups: Slides https://speakerdeck.com/marakana/ne-scala-2012-the-typeclass-pattern-an-alternative-to-inheritance https://speakerdeck.com/marakana/ne-scala-2012-the-typeclass... https://dl.dropbox.com/u/1679797/NE%20Scala/Bakery%20from%20the%20Black%20Lagoon.pdf https://dl.dropbox.com/u/1679797/NE%20Scala/Bakery%20from%20... videos of above: http://marakana.com/s/post/1397/2013_northeast_scala_symposium_videos http://marakana.com/s/post/1397/2013_northeast_scala_symposi...