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wycats's profile
Yehuda Katz 🥨
Yehuda Katz 🥨
Yehuda Katz  🥨
Verified account
@wycats

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Yehuda Katz  🥨Verified account

@wycats

Tilde Co-Founder, OSS enthusiast and world traveler.

Portland, OR
yehudakatz.com
Joined August 2007

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    1. Yehuda Katz  🥨‏Verified account @wycats Sep 7
      Replying to @wycats @graydon_pub @samth

      I can say what I was trying to say a little more strongly: I strongly agree that today's generic system sucks both in terms of noise burden AND in terms of how closely it matches programmer intuition about parameterized types and functions.

      2 replies 0 retweets 0 likes
    2. Nasal Demon‏ @ubsanitizer Sep 7
      Replying to @wycats @graydon_pub @samth

      I think you could probably argue the same for functions - before someone gets an intuition for what [type] functions are, [type] functions are confusing. They don't actually seem that hard, especially if you remove all the complicated (implicit or explicit) interface stuff

      3 replies 0 retweets 0 likes
    3. Yehuda Katz  🥨‏Verified account @wycats Sep 7
      Replying to @ubsanitizer @graydon_pub @samth

      I don't think so, at least for me. I know both concepts extremely well (to the point of having written both frameworks using the concepts and implementations of the concepts), and type parameters feel much harder to me.

      1 reply 0 retweets 0 likes
    4. Yehuda Katz  🥨‏Verified account @wycats Sep 7
      Replying to @wycats @ubsanitizer and

      Part of that is because when types feel "easy", it's possible to mentally elide them and focus on normal function execution. But type parameters require you to first run a "type interpreter" in your head to understand what you're looking at.

      1 reply 0 retweets 0 likes
    5. Yehuda Katz  🥨‏Verified account @wycats Sep 7
      Replying to @wycats @ubsanitizer and

      I think this is the explanation for why people have an intuition that parameters are existentials: it's much easier to avoid the "type interpreter" step when you think about them that way.

      2 replies 0 retweets 1 like
    6. Sam Tobin-Hochstadt‏ @samth Sep 7
      Replying to @wycats @ubsanitizer @graydon_pub

      I think I (maybe like @ubsanitizer) don't understand the mental model you're describing. I think about (and teach) type parameterization as a precise analogue of function parameterization. You have two similar things (functions, type defs), and you abstract by adding a parameter.

      1 reply 0 retweets 2 likes
    7. Nasal Demon‏ @ubsanitizer Sep 7
      Replying to @samth @wycats @graydon_pub

      Right, that's my mental model of type parameters. I know functions are really hard to "get" before you have the intuition; I imagine type parameters are the same way.

      1 reply 0 retweets 0 likes
    8. Nasal Demon‏ @ubsanitizer Sep 7
      Replying to @ubsanitizer @samth and

      (but once you have that intuition, then you're fine)

      1 reply 0 retweets 0 likes
    9. Yehuda Katz  🥨‏Verified account @wycats Sep 7
      Replying to @ubsanitizer @samth @graydon_pub

      I agree with this model, but do you agree that you first have to mentally instantiate the function with types before you can mentally instantiate it with parameters?

      1 reply 0 retweets 0 likes
    10. Sam Tobin-Hochstadt‏ @samth Sep 7
      Replying to @wycats @ubsanitizer @graydon_pub

      Only if you need to typecheck the function (perhaps if you need to do that in order to figure out what the function does in the first place because static types determine runtime behavior).

      1 reply 0 retweets 0 likes
      Yehuda Katz  🥨‏Verified account @wycats Sep 7
      Replying to @samth @ubsanitizer @graydon_pub

      an earlier sub-thread in this chain stated (without objection) that a mismatch between parameter and existential intuitions is the source of problems. Did I misunderstand that? Can you elaborate?

      11:43 AM - 7 Sep 2018
      2 replies 0 retweets 0 likes
        1. New conversation
        2. Sam Tobin-Hochstadt‏ @samth Sep 7
          Replying to @wycats @ubsanitizer @graydon_pub

          The existential intuition is wrong, just like lots of wrong intuitions about functions are wrong. I think you said that people use the existential intuition because it's simpler, but I disagree that it's simpler than the abstraction intuition I described.

          1 reply 0 retweets 1 like
        3. Nasal Demon‏ @ubsanitizer Sep 7
          Replying to @samth @wycats @graydon_pub

          I actually literally don't understand the existential model people apparently have...

          0 replies 0 retweets 1 like
        4. End of conversation
        1. New conversation
        2. Paolo G. Giarrusso‏ @Blaisorblade Sep 8
          Replying to @wycats @samth and

          Paolo G. Giarrusso Retweeted Vincent Esche

          You mean https://twitter.com/regexident/status/1037996144893349891?s=21 … ? That’s about Swift protocols, but those do *seem* different from System F and much closer to existentials (better: to Scala abstract type members or ML translucent sums). OTOH, it seems they cut out many features of type members?

          Paolo G. Giarrusso added,

          Vincent Esche @regexident
          Replying to @graydon_pub @anandabits and 2 others
          This right there is the story of generic protocols and Swift. 9 out of 10 people talking about them actually mean existentials (or HKTs), making it almost impossible to start a healthy discussion about (e.g. the possibility of adding) the former in a productive way. 🙁
          1 reply 0 retweets 0 likes
        3. Nasal Demon‏ @ubsanitizer Sep 8
          Replying to @Blaisorblade @wycats and

          what do people man when they're saying existentiels

          2 replies 0 retweets 0 likes
        4. Nasal Demon‏ @ubsanitizer Sep 8
          Replying to @ubsanitizer @Blaisorblade and

          *mean in this thread

          1 reply 0 retweets 0 likes
        5. Nasal Demon‏ @ubsanitizer Sep 8
          Replying to @ubsanitizer @Blaisorblade and

          what is wrong with my keyboard

          0 replies 0 retweets 0 likes
        6. End of conversation

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