3 ms·

TypeScript is sort of "dynamically typed but statically verified".

nine_k 2y ago
Much like C++ then — the machine code to which it translates lacks types! A TS compiler will reject an ill-typed program. You of course can just strip the type syntax and get a valid (though buggy) JavaScript code.
- LoganDark 2y ago
  > Much like C++ then — the machine code to which it translates lacks types! Ehh, not exactly. Most C++ compilers won't output machine code for inputs they don't understand. Though of course, you could simply translate some C++ code yourself into machine code and then say C++ is just like TypeScript in that way. "If you turn C++ into machine code, the machine code lacks types!" "If you turn TypeScript into JavaScript, the JavaScript lacks types!" The main difference is the C++ compiler won't generate machine code for you if the code you provided it doesn't compile, but the TypeScript compiler essentially treats types as a lint (unless extended by compiler plugins such as `typescript-is`, which I greatly enjoyed back in the day). Also, CHERI begs to differ. And even other than that, machine code isn't dynamically typed because it's not typed at all. Usually, everything is data (usually even the machine code itself, except on Harvard architectures), aside from any architecture-specific memory protections (and other protections), if applicable. I could probably go on about this for days. > A TS compiler will reject an ill-typed program. You of course can just strip the type syntax and get a valid (though buggy) JavaScript code. Can't Deno execute TypeScript directly? Last I checked, it didn't do typechecking itself because [the size and complexity of tsc]. For what that's worth, cling also exists, so try tricking that into executing compiler errors. I don't think it would.
  - mabster 2y ago
    I would argue that machine code is typed, but this will be up to interpretation. I.e. you can add two 32 but floating point numbers or two 16 bit integers or store an 8 bit value. It's just doesn't require you to purposefully type pun in some circumstances (e.g. where floating point and integer registers are shared).
    - jerf 2y ago
      A "typed" machine code would imply that you can say "Add these two 32-bit floating points" and the CPU will say "No, I can't, those are 4 8-bit unsigned integers". I don't believe the CPU will ever say that, so it is not typed by any sensible measure. Best you can do is that there may be some registers that can only be used by floating point units and others that can only be used by ints, but even that is really just hardware limitations for performance and not any sort of type assertion; the CPU will happily bit-slam them back and forth without anything like an "exception".
  - weinzierl 2y ago
    "And even other than that, machine code isn't dynamically typed because it's not typed at all." Well, we have bytes, words, doublewords and quadwords on the machine level. They are usually referred to as data types in the processor manuals.
    - nine_k 2y ago
      I'd say that instructions are typed, but data are not. You can use an integer arithmetic, bit manipulation, floating point arithmetic, or vector SSE instruction on the very same data in the very same register, and it will just work without any complaints for most bit patterns. A CPU of course does analyze the code, but only the short segment currently in the pipeline, and not for any high-level semantics, just for data dependencies and very local jumps.
  - nine_k 2y ago
    > TypeScript compiler essentially treats types as a lint Sorry, I think you've been swindled. The Typescript compiler is made by Miscrosoft and is called tsc. It very much heeds the type annotations, and very much rejects ill-typed programs. An LSP based on it does the same in an editor. Also tsc supports refinement types via flow control analysis and a bunch of other static correctness checks. Deno, bun, swc are not true compilers like tsc, they don't do much correctness checking at all. They discard al the type info, and then operate on pure JS (modules conversion, minification, etc).
    - nurettin 2y ago
      I think they are confused by the tslint project, which is different than tsc and is not supported by Microsoft
      - nine_k 2y ago
        Or maybe even https://github.com/bloomberg/ts-blank-space https://github.com/bloomberg/ts-blank-space But I bet on swc, which is used by Deno internally, or on the Bun's built-in transpiler that does things similar to swc or ts-blank: they all assume that the code is semantically correct (not just syntactically valid) Typescript, and then just ignore the Typescript-specific bits.
      - LoganDark 2y ago
        I used tsc directly to develop https://github.com/LoganDark/waifu2x-unlimited https://github.com/LoganDark/waifu2x-unlimited. I have experience with tsc.
    - debugnik 2y ago
      > and very much rejects ill-typed programs No it doesn't. Even on the strictest settings, Typescript is unsound in trivial ways, which I hit every time I use it in anger (e.g. undefined in unassigned variables). And Microsoft libraries seem perfectly ok with asserting their type errors away without any validation, specially for JSON values. I had a similar experience with Python until I found Pydantic. I haven't had a chance to try Elixir's new type system (is it ready yet?), but at least their strong-arrow model would ensure that runtime checks for dynamically-typed values are done eventually.

Much like C++ then — the machine code to which it translates lacks types! A TS compiler will reject an ill-typed program. You of course can just strip the type syntax and get a valid (though buggy) JavaScript code.

LoganDark 2y ago
> Much like C++ then — the machine code to which it translates lacks types! Ehh, not exactly. Most C++ compilers won't output machine code for inputs they don't understand. Though of course, you could simply translate some C++ code yourself into machine code and then say C++ is just like TypeScript in that way. "If you turn C++ into machine code, the machine code lacks types!" "If you turn TypeScript into JavaScript, the JavaScript lacks types!" The main difference is the C++ compiler won't generate machine code for you if the code you provided it doesn't compile, but the TypeScript compiler essentially treats types as a lint (unless extended by compiler plugins such as `typescript-is`, which I greatly enjoyed back in the day). Also, CHERI begs to differ. And even other than that, machine code isn't dynamically typed because it's not typed at all. Usually, everything is data (usually even the machine code itself, except on Harvard architectures), aside from any architecture-specific memory protections (and other protections), if applicable. I could probably go on about this for days. > A TS compiler will reject an ill-typed program. You of course can just strip the type syntax and get a valid (though buggy) JavaScript code. Can't Deno execute TypeScript directly? Last I checked, it didn't do typechecking itself because [the size and complexity of tsc]. For what that's worth, cling also exists, so try tricking that into executing compiler errors. I don't think it would.
- mabster 2y ago
  I would argue that machine code is typed, but this will be up to interpretation. I.e. you can add two 32 but floating point numbers or two 16 bit integers or store an 8 bit value. It's just doesn't require you to purposefully type pun in some circumstances (e.g. where floating point and integer registers are shared).
  - jerf 2y ago
    A "typed" machine code would imply that you can say "Add these two 32-bit floating points" and the CPU will say "No, I can't, those are 4 8-bit unsigned integers". I don't believe the CPU will ever say that, so it is not typed by any sensible measure. Best you can do is that there may be some registers that can only be used by floating point units and others that can only be used by ints, but even that is really just hardware limitations for performance and not any sort of type assertion; the CPU will happily bit-slam them back and forth without anything like an "exception".
- weinzierl 2y ago
  "And even other than that, machine code isn't dynamically typed because it's not typed at all." Well, we have bytes, words, doublewords and quadwords on the machine level. They are usually referred to as data types in the processor manuals.
  - nine_k 2y ago
    I'd say that instructions are typed, but data are not. You can use an integer arithmetic, bit manipulation, floating point arithmetic, or vector SSE instruction on the very same data in the very same register, and it will just work without any complaints for most bit patterns. A CPU of course does analyze the code, but only the short segment currently in the pipeline, and not for any high-level semantics, just for data dependencies and very local jumps.
- nine_k 2y ago
  > TypeScript compiler essentially treats types as a lint Sorry, I think you've been swindled. The Typescript compiler is made by Miscrosoft and is called tsc. It very much heeds the type annotations, and very much rejects ill-typed programs. An LSP based on it does the same in an editor. Also tsc supports refinement types via flow control analysis and a bunch of other static correctness checks. Deno, bun, swc are not true compilers like tsc, they don't do much correctness checking at all. They discard al the type info, and then operate on pure JS (modules conversion, minification, etc).
  - nurettin 2y ago
    I think they are confused by the tslint project, which is different than tsc and is not supported by Microsoft
    - nine_k 2y ago
      Or maybe even https://github.com/bloomberg/ts-blank-space https://github.com/bloomberg/ts-blank-space But I bet on swc, which is used by Deno internally, or on the Bun's built-in transpiler that does things similar to swc or ts-blank: they all assume that the code is semantically correct (not just syntactically valid) Typescript, and then just ignore the Typescript-specific bits.
    - LoganDark 2y ago
      I used tsc directly to develop https://github.com/LoganDark/waifu2x-unlimited https://github.com/LoganDark/waifu2x-unlimited. I have experience with tsc.
  - debugnik 2y ago
    > and very much rejects ill-typed programs No it doesn't. Even on the strictest settings, Typescript is unsound in trivial ways, which I hit every time I use it in anger (e.g. undefined in unassigned variables). And Microsoft libraries seem perfectly ok with asserting their type errors away without any validation, specially for JSON values. I had a similar experience with Python until I found Pydantic. I haven't had a chance to try Elixir's new type system (is it ready yet?), but at least their strong-arrow model would ensure that runtime checks for dynamically-typed values are done eventually.