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wcrichton's profile
Will Crichton
Will Crichton
Will Crichton
@wcrichton

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Will Crichton

@wcrichton

Articulating the ineffable. Programming language theory 🤝 cognitive psychology. PhD @Stanford

he/him
willcrichton.net
Joined September 2011

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    1. Will Crichton‏ @wcrichton 21 Jul 2020

      Are there any programming languages with *intentionally* unsound static type systems?

      13 replies 6 retweets 21 likes
    2. Josh Horowitz‏ @qualmist 21 Jul 2020
      Replying to @wcrichton

      Does TypeScript count? https://www.typescriptlang.org/docs/handbook/type-compatibility.html … says things like "The places where TypeScript allows unsound behavior were carefully considered", which sounds like what you're looking for.

      1 reply 0 retweets 12 likes
    3. Will Crichton‏ @wcrichton 21 Jul 2020
      Replying to @qualmist

      Will Crichton Retweeted Will Crichton

      It does, although I'm realizing "sound" is hard to characterize. In a PLT sense, Typescript statics + dynamics are collectively sound b/c anything not caught by type system is checked at runtime. No stuck states / UB / segfaults / etc.https://twitter.com/wcrichton/status/1285700061712785408 …

      Will Crichton added,

      Will Crichton @wcrichton
      Replying to @wcrichton @nick_r_cameron
      Hmm, the original tweet may be poorly phrased. This is the kind of example I want, but the Dart type system is still sound here when paired with runtime checks. Like soundness of gradual typing.
      6 replies 0 retweets 2 likes
    4. Josh Horowitz‏ @qualmist 21 Jul 2020
      Replying to @wcrichton

      I can't quite see how a segfault is different (in practice) from "undefined is not a function". Is it caught-by-OS vs. caught-by-interpreter that you are noting here?

      2 replies 0 retweets 0 likes
    5. Will Crichton‏ @wcrichton 21 Jul 2020
      Replying to @qualmist

      Putting the PL theory hat on... If Javascript had a formal language semantics, "Undefined is not a function" would be listed as a rule. If C had a formal language semantics, *NULL would not be listed as a rule, i.e. have no semantic meaning defining the behavior.

      1 reply 1 retweet 0 likes
      Will Crichton‏ @wcrichton 21 Jul 2020
      Replying to @wcrichton @qualmist

      In practice, we define *some* kind of semantics for UB, often punted to a different computation layer (e.g. the OS). But from a PL design perspective, it's important to know whether a program can enter a state for there's no official semantics.

      4:11 PM - 21 Jul 2020
      0 replies 0 retweets 0 likes

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