Borrow-checking without type-checking(scattered-thoughts.net) |
Borrow-checking without type-checking(scattered-thoughts.net) |
x^
x*
It seems like either one evaluates the contents of the `box`, and would only make a difference if you tried to use `x` afterwards? Essentially if you final-line eval `x^` and then decide you want to continue that snippet, you can't use `x` anymore because it's been moved. Awkwardly, it also hasn't been assigned so I'm not sure the box is accessible anymore?
More or less. x^ moves the whole box whereas x* copies the contents of the box.
> Awkwardly, it also hasn't been assigned so I'm not sure the box is accessible anymore?
Yes, if you move something and don't assign it then it gets dropped, same as rust.
> Most people who think they have a problem with dynamic typing actually have a problem with weak typing.
Ironically, I would counter that, in my experience, most people who have a problem with static typing actually have a problem with verbose type systems, like Java's or C++'s — or Rust's. (Rust is at least gaining something for its verbosity.)
Type inference is a neat way to bridge the gap. OCaml, Haskell, and Swift (to name a few) all feature distinct type inferencing that give you the benefits of static types without as much syntactic overhead.
It's not just Python too, I've hit the same issue in Common Lisp.
Yes one can run contracts and unit tests and static analysis, but what's a type checker anyway other than a very strict static analysis tool?
No, the real actual problem is with invisibility aka: the absence of readability:
In a "dynamic typing" program the interpreter knows what `a` is but YOU not.
In very strong sense. You can imagine that `a` is a `int` because, well, you write the program, right? But in fact, is only probabilistic assumption.
Some day, `a` will be a program that delete the files of your computer.
It is no accident that all mainstream dynamic languages now have optional typing support, either in the language directly or via linters.
The correct term for languages that don’t have syntactic types is “untyped”.
> Most people who think they have a problem with dynamic typing actually have a problem with weak typing.
All people who say things like this have never studied computer science.
The point of types is to prove the absence of errors. Dynamic typing just has these errors well-structured and early, but they're still errors.
"syntactic type" is a weird term to me, though. Is that in common use?
I used "syntactic type" to underscore that formally, typing is a syntactic system that assigns types to terms, where terms are syntactic expressions.
Because of that, it's usually redundant to include "syntactic". You'll typically see it used when it's being contrasted to some other less standard approach to typing, e.g.: https://blog.sigplan.org/2019/10/17/what-type-soundness-theo...
As for type errors, the strictness that static typing enforces is simply not needed in the majority of cases. And in the ones where it is needed, most languages I know provide a way for you to enforce the usage of the correct type.
Maybe for you. Originally static typing was to make the job of the compiler easier. Dynamic typing was seen as a feature that allows for faster prototyping.
And no, dynamic typing does not mean untyped. It just means type errors are checked at runtime instead of compile time.
You can have strongly typed dynamic languages. Common Lisp is a very good example.
Weak typing is a design mistake. Dynamic typing has its place as it allows you to have types that are impossible to express in most static type systems while avoiding the bureaucratic overhead of having to prematurely declare your types.
The best languages allow for gradual typing. Prototype first then add types once the general shape of your program becomes clear.
> It just means type errors are checked at runtime instead of compile time.
This is a fundamental misconception. A type checker proves the absence of errors. It doesn't check for error conditions. That is: A program that isn't (cannot be proven to be) well-typed can very well be correct. But a program that is well-typed is guaranteed to be free from certain errors.
What you call "dynamically typed", in contrast, is comsequent just value inspection and stopping the evaluation/execution early. A program that has been executed successfully often is not necessarily correct.
If you want to apply the same operation on all of them, then they share some API commonality -- therefore you can use polymorphism or type erasure.
If they don't, you still need to know what types they are -- therefore you can use `std::variant`.
If they really are unrelated, why are you storing them together in the same container? Even then, it's trivial in C++: `std::vector<std::any>`.