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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. Graydon Hoare‏ @graydon_pub Sep 3
      Replying to @graydon_pub @wycats

      Many users have experienced "my program is simple, but type system is so complex that I can't for the life of me get it to typecheck" which is .. a thing you want to reserve for only the gravest / most-pervasive problems if you want anyone to have the patience to use the thing.

      2 replies 1 retweet 11 likes
    2. Sam Tobin-Hochstadt‏ @samth Sep 3
      Replying to @graydon_pub @wycats

      My experience is that mostly people who want their simple program to type check are asking for either significantly greater type system complexity or to be able to ignore some aspect of the underlying language (such as concurrency or mutability).

      2 replies 0 retweets 7 likes
    3. Graydon Hoare‏ @graydon_pub Sep 3
      Replying to @samth @wycats

      IME it's more often subtle misreadings in the user's model of the type system, such as mistaking type envs / bindings for values, mistaking static bounds for existentials, wrong model of unification, variance, implicits, interaction with subtyping, etc.

      3 replies 1 retweet 11 likes
    4. Graydon Hoare‏ @graydon_pub Sep 3
      Replying to @graydon_pub @samth @wycats

      I.e. the user doesn't want an unsafe or wrong program as such, they just have typed what they want in a way that doesn't quite fit with the way the type system wants to describe or deduce it, and they can't find the place where it differs.

      2 replies 3 retweets 22 likes
    5. Yehuda Katz  🥨‏Verified account @wycats Sep 3
      Replying to @graydon_pub @samth

      I totally agree with this diagnosis! But I think it implies we should look harder at the standard ways we express typed programs to see why there problems come up over and over, and try to tweak the trade-offs.

      1 reply 0 retweets 6 likes
    6. Graydon Hoare‏ @graydon_pub Sep 3
      Replying to @wycats @samth

      Agreed. This is where I point to generics as "a standard way we express typed programs" and express some ambivalence. Perhaps a bit like my ambivalence over (say) lambdas. They work, but it seems they introduce a lot of room for mismatched meanings.

      2 replies 0 retweets 4 likes
    7. Yehuda Katz  🥨‏Verified account @wycats Sep 3
      Replying to @graydon_pub @samth

      The existence of uninstantiated type parameters is kind of there under the surface no matter what you do, but I completely agree that the syntax of generics that most languages use is a weak local maximum.

      1 reply 0 retweets 5 likes
    8. 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
    9. 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
    10. 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
      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.

      9:47 AM - 7 Sep 2018
      1 reply 0 retweets 0 likes
        1. New conversation
        2. 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
        3. 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
        4. 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
        5. 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
        6. 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
        7. 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
        8. 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?

          2 replies 0 retweets 0 likes
        9. 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
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